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The study of natural hazard interrelations exposes the complexity of extreme climatological, geophysical and hydrological processes and poses new science challenges. This PhD thesis is located at the confluence of multivariate statistics, climatology and natural hazard modelling and aims to provide new approaches to model and quantify natural hazard interrelations. Chapter 2 consists of a critical literature review of 146 sources. From these, the historical context for quantitative single-hazard and multi-hazard assessment is discussed, and 19 different modelling methods to model multi-hazard interrelations are identified and organized into three broad approaches (empirical, stochastic, mechanistic). Chapter 3 examines the multi-hazard landscape of the European Atlantic Region (EAR) but has global relevance in its application. A total of 16 relevant natural hazards for the EAR region are identified on three main criteria: (i) frequency of occurrence, (ii) spatial relevance, (iii) potential to impact energy infrastructures. Based on the knowledge of hazard interrelations and physical drivers, natural hazards are grouped into five multi-hazard networks. Through a review of 32 single hazard catalogues, 50 historic major multi-hazard events in the EAR are pinpointed for each network. Within each network, the prevalence of each hazard interrelation is discussed. After identifying the main modelling approaches and dominant hazard interrelations in the EAR, the abilities of a group of modelling method for multi-hazard modelling is assessed. Chapter 4 evaluates the efficacy of bivariate extreme modelling approaches for multi-hazard scenarios. Six bivariate extreme models are evaluated and compared by using each model's fitting capabilities to 60 synthetic datasets. The properties of the synthetic datasets are matching bivariate time series of environmental variables. The systematic framework contrasts model strengths (model flexibility) and weaknesses (poorer fits to the data). The benefits of this framework are highlighted with two applications to natural hazard interrelation modelling. Using the findings of Chapter 3, two pairs of natural hazard are selected: extreme hot temperature-wildfire; extreme wind-extreme rainfall. Chapter 5 analyses the spatiotemporal features of hazard interrelations using climate reanalysis data for two hazards (extreme wind and extreme rainfall) for 1979-2019 within a region including Great Britain and the British channel. A clustering algorithm is used to create hazard clusters with extreme values (above the 99% quantile) of hourly precipitation and wind gust. A total of 4555 compound wind-rainfall clusters are detected for 1979-2019 by assessing the spatiotemporal overlap of the two hazards. The characteristics (e.g., size, duration, season, intensity) of created clusters are confronted with observations and analysed. One of the bivariate modelling methods assessed in Chapter 4 is used to estimate return periods of compound hazard events. The relationship between the return period of compound hazard events and the spatial and temporal attributes of compound hazards events is then analysed. Throughout the thesis, the following main aspects of a quantitative multi-hazard approach are addressed: interrelation characterisation, multivariate modelling, physical drivers, spatiotemporal overlap, data. Robust solutions to identify, discriminate and model hazard interrelations at different spatial and temporal scales are offered.

Climate has changed throughout geological history as part of the natural process, which consequently altered the extent and the level of seas. However, the rate of these changes has accelerated from the second half of the last century. There is much scientific evidence that climate change has and will continue to accelerate the rate of sea level rise in the 21st century. This creates a significant risk for many countries in terms of flooding, coastal erosion and wetland inundation, which in turn will impact human communities (socially and economically) and ecosystems. It is therefore vital to have reliable strategies for modelling and reducing the impact of climate change. This study provided a methodology based on geospatial technology to provide stakeholders with a decision-making tool for better understanding of uncertainties in climate change study and future flood defence planning. This study integrated the uncertainties from both DEM and RCPs to provide a better projection of flooding that results from sea level rise. The study also looked at the errors and the spatial autocorrelation aspect and provides evidence that the independency of the error did not improve the outcomes significantly. Identifying the critical area in studying sea level rise inundation is crucially important for the decision makers to plan to and prevent future flooding by building barriers. This study developed a method to include the factors affecting the site selection by integrating the multi-criterial evaluation with GIS tool for site selection. In Qatar and many other countries, industrial activities, especially from the oil and gas industry, are concentrated in the coastal areas. The economic benefit of protecting the coastal areas from flooding is important for the wider economy of the country. Therefore, prioritising the areas based on the risk of flooding and identification of the critical areas to build barriers will help in making decisions on future investments by governments and companies operating in those areas.

This thesis aims to enhance the current understanding of the response of SW Iberian ecosystems to abrupt and orbital-scale climate changes. The last ~28 thousand years can provide such insight, containing several abrupt North Atlantic climate events superimposed on orbital-scale global changes. This study presents new high-resolution pollen and leaf-wax n-alkane records combined with palaeoceanographic proxies from the same deep-sea cores (SHAK06-5K and MD01-2444) on the Southwestern (SW) Iberian Margin. The chronology of these records is based on high-resolution Accelerator Mass Spectrometry radiocarbon dating of planktonic foraminifer Globigerina bulloides from cores SHAK06-5K and MD01-2444. Changes in temperate and steppe records during the Last Glacial Maximum and subsequent deglaciation are closely coupled with changes in sea surface temperatures (SSTs), and global ice volume. This coupling continues during the onset of the Holocene, with the peak in thermophilous woodland lagging the boreal insolation maxima by ~2 kyr. This possibly arises from the persistence of residual high-latitude ice-sheets into the Holocene. A close correlation between rapid oscillations in pollen percentages and millennial/centennial-scale variations in SSTs, planktonic 18O, and lithology suggests extrinsically-forced SW Iberian ecosystem changes in response to abrupt North Atlantic climate events. In contrast, the abrupt thermophilous woodland decline at ~7.8 thousand years before present (cal ka BP) indicates an intrinsically-mediated abrupt vegetation response to the gradually declining boreal insolation, resulting in the crossing of an ecological threshold. The leaf-wax n-alkane 13C record from SHAK06-5K combined with the pollen record from the same core and modern leaf-wax n-alkane 13C data from SW Iberia suggest that this geochemical proxy is directly or indirectly driven by SW Iberian climate variations. Two potential mechanisms are proposed: i) n-alkane 13C is directly controlled by changes in regional moisture availability; or ii) climate change leads to a turnover of plant species with inherently different n-alkane 13C signatures.

Weather phenomena have long been objects of studies in atmospheric and climate science research. Studies on weather phenomena incorporate meteorological data, climate model simulations, and knowledge of physical processes of the Earth's atmosphere. Understanding of the developing mechanisms, life cycles, and spatiotemporal dependencies of these phenomena requires accurately identifying them in space and time. Moreover, identifying weather phenomena in large-scale climate model simulations is critical for advancing our understanding of the Earth's climate and risks of future extreme weather events. The main goal of this thesis is to design and develop pattern recognition methods that directly learn from examples of weather phenomena in climate data, rather than following heuristic algorithms containing threshold requirements on physical variables. In particular, we aim to classify and localise atmospheric river and blocking phenomena in global climate simulations and reanalysis data. In this thesis, we propose a novel pattern recognition method for identifying atmospheric river phenomena in climate datasets. This method consists of topological data analysis and machine learning methods. We demonstrate that the proposed method is reliable, robust, and achieves high accuracy. Also, we test the method on a wide range of spatial and temporal resolutions of global climate model outputs. We find that the method achieves the highest classification accuracy for low-resolution climate model outputs. Moreover, we propose a hierarchical pattern recognition method for identifying atmospheric blocking phenomena in climate reanalysis products. This pattern recognition method is based on deep convolutional neural networks. We demonstrate that the proposed method accurately detects and localises atmospheric blocks in climate reanalysis data. We also find that the method achieves higher accuracy for classification and lower estimation error for localisation of blocking phenomena in regions of the Northern Hemisphere than in regions of the Southern Hemisphere. Research outcomes presented in this thesis show that the proposed pattern recognition methods can be complementary tools to the existing identification methods of atmospheric rivers and blocks in climate data. In addition to that, the proposed methods offer automatic post-processing, quantitative assessment of climate datasets, and can facilitate analysis of the local impacts of weather phenomena on specific geographical areas.

The global response to climate change depends on you ... and everyone else. The decisions we make, for better or worse, contribute to the global response. This study explores decision making, climate change signals and responses, actors and interests, and the "conditions" under which we might limit climate change and related impacts. Twenty-seven experts from around the world were asked to provide scenarios where the global response succeeds or fails to limit climate change and related impacts (i.e. the UNFCCC objective). From their responses, 175 scenarios were compiled forming a "searchable sample of possible futures". Themes included social change and behaviour, political will and policy, business and economic activity. For these themes, multiple "pathways" were mapped. The study focused on pathways towards effective global responses (i.e. fulfilling the UNFCCC objective) and understanding the most important elements of the response system. The study finds there is a "crisis of response" that risks becoming a "crisis of impacts". The signal that drives effective responses (i.e. impacts on people, property and livelihoods) was undetectable, is detectable now, and is rapidly strengthening. As such, timely global responses at scale are essential. Other preconditions include a mix of ambition and serendipity. From the analysis of effective response scenarios, serendipitous preconditions include the scale of climate change and related impacts being limited and reversible meanwhile unexpected events help limit climate change or related impacts. Ambition driven preconditions include global responses being timely with adaptation, mitigation and atmospheric GHG removals at scale, and having contingencies available in case of extreme climate change or other unexpected events. The transformative scale of required responses means social permissions and leadership are essential, as are coalitions of actors with the capacity to apply technologies and practices (policies included) and power to ensure each of us are contributing towards effective global responses.

Despite anthropogenically induced climate change being viewed by many as one of the greatest societal challenges of the 21st century, discernment from the public, especially young people, remains under explored within the mitigation debate. This is surprising given research demonstrating the potential for collective action to reduce greenhouse gas emissions nationally through individual behaviour changes. Young people are those in society that will live with the effects of future climate change the longest but are typically overlooked in forward planning. Consequently, this PhD thesis aims to provide detailed understanding of intersecting perception of climate change and levels of engagement being undertaken to explore how people, particularly the young, are reacting to climate change. The nexus of these themes was explored using a mixed method approach through the use of primary data collection, including interviews (N = 5), two national surveys (N = 1,134, survey 1 and N = 1,700, survey 2) and a participatory workshop using the Yonmenkaigi System Method approach (N = 16). In addition, this primary data is cross-analysed through the use of secondary data (BEIS and Eurobarometer) to extrapolate a more comprehensive picture based on the case of the United Kingdom. The research found that in the United Kingdom (and implicitly elsewhere) there are high-levels of perception of climate change as a major concern, especially amongst young people, and more extensively since 2013 when a social tipping point around this issue occurred. This has occurred despite of the 'finite pool of worry', a theory suggesting a likely plateauing or decline in concern when other crises start to predominate in people's day to day, such as during the aftermath of the Brexit vote, COVID-19 and associated economic uncertainty. In terms of youth and perception, this thesis found that whilst young people were the most likely to believe a climate change was happening and most likely to view that climate change is a serious problem, they were one of the least likely group of people to be able to determine what impacts were already being felt within the United Kingdom due to climate change. Although there is this high level of belief in climate change amongst young people and civil society more widely, the level of engagement through mitigation strategies varies. Those strategies that are behavioural are generally undertaken, especially among the youngest in society and those who view climate change as serious. However, this applies when there is substantive investment. This demonstrates that if the government wants to implement significant change through the will of society to reduce greenhouse gas emissions, investment for those on low incomes is needed to enable the requisite behaviour change needed. This research also confirms a view, as iterated by many of its respondents, that education on climate change within the United Kingdom is lacking; application of participatory methods, such as the Yonmenkaigi System Method, demonstrated how education would progress the interconnection between perception and engagement. This study recognises complexity involved in the interconnection between perception, engagement and reaction. However, it is argued that if social media generates fake news especially around climate change, then young people who are the most personal users of social media should be the most exposed. The results show that they are the most believing of climate change and that it is likely social media self-reinforces consistent beliefs through echo chambers. Into the current lacuna of action by the government during this PhD research period, climate activism groups of 'Extinction Rebellion' and 'School Strikes for Climate Change' materialised. It is argued that the actions of these groups are a form of 'post-normal engagement', where people apply their understanding, and that arises through a lack of facilitation of 'post-normal science' in relation to climate change within the United Kingdom. It was found that the majority of survey respondents were overall supportive of "Extinction Rebellion". In addition, it was found that there was also a majority of support for the children striking for climate change and the mass civil disobedience that "Extinction Rebellion" called for in London in April 2019, though at varying levels across the demographic. However, respondents were generally not willing to themselves join future "Extinction Rebellion" protests. Women, younger people and left-leaning voters were more likely to support these two types of protests. The monitoring of the demographic composition of climate protests in terms of perception and engagement drivers helps to assess the nature of likely reactions and resistance to future climate policy including that associated with the content of COP26 being hosted in the UK during 2021. However, the implementation of a post-normal climate change science might help reduce the need for climate activism.

As I write, climate change scientists are predicting that, unless we take immediate and radical action, this century will end in catastrophic climate change. My daughter is 19, she has already lived through the 18 hottest years, since records began (Nasa, 2020). The IPCC reports she will, in her lifetime, see dramatic changes to the climate that are likely to severely impact food growing and supplies, endanger species' and wildlife and lead to large scale human migration, with the likely potential of small and large scale conflicts in the face of scarcity of resources. On this theme, BBC Radio 4 ushered in the third decade of the 21st century by bringing together wildlife presenter David Attenborough and teenage climate change activist Greta Thunberg to share their perspectives on the climate emergency. During the broadcast these two generations, representing the two extremes of a lifespan, shared their frustrations at a lack of adequate government action. In the same programme Greta's father, Svante, gave an interview, something which happens rarely given his daughters fame. During the discussion he admitted, despite travelling the globe supporting his daughter's campaign, he does not himself identify as a climate activist. Indeed he says he has only ever wanted to support Greta, not to save a planet, but so that she, and her sister, are happy. Prior to Greta becoming an activist she had suffered from depression which had included her going on hunger strike for three months, a difficult thing for a parent to watch. Once she started the school climate strikes her depression lifted and, as Svante pointed out to the interviewer, wouldn't any parent be happy if their child started being happy and eating again? Svante Thunberg's comments offer a good starting point for the topic and interest of my research; in the face of overwhelming (and frightening) evidence of global warming he does not become a climate activist, instead he sees himself as just a devoted father, motivated to support his daughter to flourish and be happy. Svante is like most of us who, in the face of significant evidence of long term threats (alcohol consumption, obesity, lack of a pension, climate catastrophe) fail to respond in the most rational way. Rather, we do what we think will work best in the short term, based not on evidence, but on how we feel, and what we see people around us are doing. We do things to support our friends and family, and in response to the demands of our many and changing contexts of home and work. My research, rooted in a career working on environmental behaviour change and social inequality, explores how emotions and perception influence our reasoning, and in turn how this affects the quality of the decisions we make, and the actions we take particularly in policy making organisations, situated in the wider context of climate and social change.

Across Europe, palaeoclimatic records dated to the Last Glacial-Interglacial Transition (LGIT; 16-8 cal. ka BP) provide evidence for several abrupt climatic oscillations on millennial and centennial-timescales. Understanding the spatial and temporal environmental response to these climatic events on a continental scale is important for providing insight into future climate scenarios. This relies on providing precise chronologies for palaeoenvironmental records, but issues with large dating uncertainties, and the practice of tuning/wiggle-matching different records together, has limited our ability to test for (a)synchroneity for abrupt climate transitions. In this study, the temporal and spatial complexity of LGIT climatic events, specifically, the Younger Dryas (YD) and earliest Holocene (EH) were investigated. Several of the most precisely dated pollen records were selected, spanning from northern to southern Europe. These sites were chosen using selection criteria that required independent chronologies based on radiocarbon dating and tephrochronology. To broaden the geographic range, a cryptotephra investigation was also undertaken on two palaeoenvironmental records from Romania (Lake Lia and Lake Brazi). Using Bayesian chronological modelling, each site's ages and the widespread tephra layers were remodelled. Pollen records were also re-investigated using the statistical methods of Principal Curve analysis to assist in identifying abrupt climatic transitions. The INTIMATE Integration tool was utilised to enable quantified comparisons between these terrestrial sites and the high-resolution Greenland ice core records. The results from the Romanian cryptotephra investigation highlight the importance of this region to expand tephrostratigraphic frameworks across Europe, the Mediterranean and Anatolia. The identification of ultra-distal tephra layers allowed for a broader investigation into the timing of LGIT events. This study showed that even with the most precisely dated sites and, despite the methodological approaches employed here, identifying a clear time-transgression for the YD and centennial-scale events within the EH remains difficult due to chronological uncertainties. Issues with proxy and dating resolutions currently limit the chronological approach undertaken. Nonetheless, using widespread tephra layers and statistical methods on proxy records can help to evaluate the potential asynchrony of abrupt climate transitions and the possible climatic drivers. Overall, this study highlights the need to provide robust chronologies by undertaking high-resolution radiocarbon dating and proxy reconstruction, supplemented by tephrochronology. By employing these approaches with Bayesian age modelling, the temporal and spatial response to abrupt climatic shifts can be further explored.

Scientists are often wary of engaging in policy advocacy as they fear it may result in the perception of bias in their science or abuse of their position. Whilst advocacy need not always result in biased science or an abuse of position, the mere suspicion that it might can be enough to deter a scientist from engaging in it. For climate scientists, this tension is well known, especially given how politically polarising action on climate change can be. This thesis identifies how, both in theory and practice, climate scientists can engage in policy advocacy in a way that is acceptable to them and their scientific community. By providing a new way of defining advocacy and the roles that scientists can engage in when communicating, I create an advocacy spectrum that maps different communication roles for scientists. Position on this spectrum is influenced by 'contextual factors' which determine how a scientist's communication may be perceived. Depending on which contextual factors are at play, even silence may be interpreted as advocacy. The advocacy spectrum is informed by semi-structured interviews with 47 climate scientists in the UK and USA. In the interviews, I explore their concerns about advocacy and the practical methods they use for managing the tensions they experience when communicating. Analysis of this data helps to further develop arguments in the theoretical literature about science communication, the role of values in science, and the conceptions about scientists as citizens in society. As a result, I identify what constitutes acceptable and unacceptable forms of policy advocacy as perceived by scientists and the scientific community. Combining the experience of climate scientists with the understanding from the theory, I then establish eight methods scientists can use that allow scientists qua scientists to engage in policy advocacy whilst also preserving their scientific credibility and independence.

The European Centre for Medium-Range Weather Forecasts (ECMWF) manages the largest archive of meteorological data in the world. At the time of writing, it holds around 300 petabytes and grows at a rate of 1 petabyte per week. This archive is now mature, and contains valuable datasets such as several reanalyses, providing a consistent view of the weather over several decades. Weather analogue is the term used by meteorologists to refer to similar weather situations. Looking for analogues in an archive using a brute force approach requires data to be retrieved from tape and then compared to a user-provided weather pattern, using a chosen similarity measure. Such an operation would be very long and costly. In this work, a wavelet-based fingerprinting scheme is proposed to index all weather patterns from the archive, over a selected geographical domain. The system answers search queries by computing the fingerprint of the query pattern and looking for close matched in the index. Searches are fast enough that they are perceived as being instantaneous. A web-based application is provided, allowing users to express their queries interactively in a friendly and straightforward manner by sketching weather patterns directly in their web browser. Matching results are then presented as a series of weather maps, labelled with the date and time at which they occur. The system has been deployed as part of the Copernicus Climate Data Store and allows the retrieval of weather analogues from ERA5, a 40-years hourly reanalysis dataset. Some preliminary results of this work have been presented at the International Conference on Computational Science 2018 (Raoult et al. (2018)).

The study of climate parameters and their feedback mechanisms have become exceedingly important in light of anthropogenic CO2 release and its initiation of climate change. In this thesis, I investigate the interaction between different climate parameters during Late Pleistocene climate cycles and the Mid-Pleistocene transition(MPT). I use ocean sediment core-derived foraminiferal shells and geochemical analyses to reconstruct surface water temperature, salinity, and atmospheric CO2 from a new site U1476 in the Mozambique Channel. I show for the first time that a peak in glacial Indian Ocean surface salinity creates a particularly salty Agulhas Leakage during Late Pleistocene deglaciations. This may influence changes in global climate by altering the surface salinity budgets at deep water convection sites, potentially driving a more vigorous overturning circulation. Late Pleistocene climate transitions established during the MPT “900kyr event”, when glacial ice volume significantly increased forming a 100kyr cycle. I demonstrate that ice sheets during the early MPT sustained glacial ice volume, despite increases in summer duration insolation and temperature. The data combined with new pCO2 reconstructions suggest that the early de-coupling of ice sheet dynamics caused a disruption in the forcing of earth’s internal feedback mechanisms, leading to the global phenomenon of the “900kyr event”. The pCO2 data was reconstructed using multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) boron isotope analysis. I present accuracy and precision data of boron isotope standard measurements conducted on a new Nu plasma II instrument. Best results were achieved after adopting a PFA cyclonic spray chamber, 1011Ω resistors, and concentrated solutions. My additional laboratory test studies provide evidence that cleaning large samples, as used in boron isotope analyses, can be efficiently conducted without the necessity for scaling reagents. My research concludes that Late Pleistocene Indian Ocean circulation and early Pleistocene ice sheet dynamics are important internal climate drivers that have the potential for shaping Pleistocene climate when coupled with insolation - or atmospheric CO2 change.

This thesis was funded by the Natural Environment Research Council (NERC) and is presented in the alternative format. The thesis comprises three separate journal articles that together form a coherent research project. The climatology of tropospheric inertial instability and the instability's effect on tropical cyclogenesis are determined in three papers. In the first paper, a hierarchy of instability criteria are derived, from which, two are used to construct global climatologies of tropospheric inertial instability using the ERA-Interim reanalysis. Seasonal occurrence maps reveal that instability is most frequent in the tropical upper troposphere of the winter hemisphere, with several local maxima of instability occurrence also identified. Synoptic composites reveal that these local maxima are associated with the midlatitude jet stream, cross-equatorial flow, and the Somali jet, as well as two previously unrecognised environments: gap wind outflow and tip jets. Furthermore, long-lived and synoptic-scale regions of instability are identified in the midlatitudes, in contrast to statements in contemporary textbooks. The effect of inertial instability on tropical cyclogenesis is then investigated via statistical and idealised numerical modelling approaches. For the statistical approach, best-track data and the ERA-Interim reanalysis are used to determine statistical relationships between inertial instability aloft and the 24-h change in mean sea-level pressure for East Pacific and North Atlantic hurricanes. No correlation is found between the spatial extent of 250-hPa instability and the 24-h intensification rates in either basin. Additionally, hypothesis testing reveals no statistical difference between the 24-h intensification rates of storms that originate in environments where the upper-tropospheric flow is predominantly inertially stable vs. storms that originate in environments where the upper-tropospheric flow contains inertial instability. Subsequently, idealised numerical modelling is used to explicitly control the inertial stability of the nascent synoptic environment via an initialised zonal jet. Although nascent synoptic environments of inertial instability are more conducive for intensification, no evidence is found to support the hypothesis that this is because the instability promotes convective outflow. Instead, we find that intensification is modulated by the environmental vertical wind shear associated with the evolution of each jet.

Interactions between multiple hazards can cause socio-economic damages that exceed those expected by the individual hazard components. Over the past decade, the multi-hazards paradigm has emerged to the extent that the Sendai Framework for Disaster Risk Reduction 2015-2030 advocated a multi-hazard approach. This thesis examines three types of concurrent hydroclimatic hazards that can occur at catchment to global scales. The first multi-hazard is the link between multi-basin flooding (MBF) and extra-tropical cyclones (ETCs) over Great Britain during the period 1975-2014. Results show that during the most geographically widespread MBF episode, up to 108 river catchments (or ~46% of the study area) recorded a peak flow annual maximum within a 16-day window. Most extreme MBF episodes were linked to cyclonic Lamb Weather Types (LWTs), atmospheric rivers and very severe gales. These episodes were associated with significant socio-economic impacts due to widespread flooding.

Ecological responses to Anthropogenic climate warming are occurring across the globe. The aim of this thesis is to critically examine knowledge gaps in: i) how assemblages respond to multidimensional temperature change; ii) patterns of realised niches across species' assemblages. I investigate these gaps to build the requisite knowledge to describe and predict assemblage scale responses to climatic warming. Chapter 2 develops a conceptual framework relating the processes of individual movements and population dynamics to the spatial and temporal dimensions of temperature change. I find that most studies do not consider the dimensionality of temperature change when quantifying assemblage dynamics. Chapter 3 finds that, on average, the abundance of reef fish species across their thermal ranges supports the 'abundant-niche centre' hypothesis. I also find a systematic pattern in the skew of realised thermal niches amongst species, which relates to latitude and biogeographic habitat variation. Chapter 4 quantifies spatial patterns in the diversity of species' responses to heatwave events in five functional groups of reef fishes on the Great Barrier Reef and western Coral Sea. Browsing herbivores, scraping herbivores and corallivores have spatially homogenous patterns of response diversity indicating resilience at a regional scale. Further, all functional groups positively respond to temperature warming but only corallivores and excavators negatively respond to coral loss, and no functional groups strongly respond to algae loss. Chapter 5 critically examines the 'wide-ranged winners' paradigm for terrestrial ectotherms (insects) across land-use types that represent a microclimatic gradient. I find that species' niche metrics consistently outperform geographic range size in predicting species occurrence. Species with warmer and drier affinities increased in occupancy in agricultural land uses which matched the expected warmer and dryer conditions. Overall, realised niches are structured by abundance, exhibit diversity within local assemblages and regional species pools, and can predict occupancy at local scales even in thermally heterogeneous terrestrial systems. This thesis therefore further establishes the thermal niche as a core concept to quantify the dynamics of assemblages in a warming world. Chapter 6 critically evaluates the benefits and limitations of this niche perspective for quantifying biodiversity change and suggests future research avenues.

Climate change induced shifts in precipitation threaten the future carbon balance of Amazon rainforests. Our understanding of water constraints to photosynthesis is largely limited to physiology-climate effects. Less is known about the effects of carbon allocation and trait shifts in response to water availability. Mechanisms linking carbon allocation and trait responses are not well represented in current ecosystem models, causing uncertainty in predicted carbon dynamics under future climates. We ask (i) What drives the coupling between photosynthesis and precipitation is it canopy structure (leaf area index; LAI), leaf traits, or solely a physiology-climate response? (ii) Why do LAI and leaf traits vary with precipitation? (iii) What is the role of water availability and plant traits in driving carbon allocation between leaves and roots? Process based modelling allows the links between photosynthesis, water availability, carbon allocation and traits to be quantified explicitly, exploring interaction space not available to insitu experiments. We calibrated the Soil Plant Atmosphere model (SPA) to eight permanent sample plots across an Amazon mean annual precipitation gradient (1400-2800mm), as part of the Global Ecosystems Monitoring network. The model's representation of local carbon fluxes was evaluated against biometric estimates. We then conducted a series of model experiments to quantify the principal drivers of photosynthesis across the precipitation gradient and explore mechanisms of LAI, leaf trait and carbon allocation responses to water availability. LAI increased with precipitation (R2=0.42, p=0.08), and was the principal driver of differences in photosynthesis across the gradient, accounting for 36% of observed variation. Differences in leaf traits accounted for 20% of variance and physiology-climate interactions accounted for a further 12%. Spatial variance in LAI was underpinned by carbon economics, and best predicted by an optimality approach that maximised net canopy carbon export (R2=0.87, p < 0.001). Across the precipitation gradient, leaf trait strategies shifted from fast to slow as water availability increased (where fast leaf traits are a cohort of high photosynthetic capacitance, high metabolic rate, high nitrogen content, low LMA and short lifespan and vice versa for slow leaf traits). Leaf traits had a determinate effect on LAI optimality, and higher leaf areas at wet plots were supported by longer leaf lifespans rather than an increase in leaf net primary production (NPP). At dry plots, short leaf lifespans, inherent of fast leaf trait cohorts, effected lower LAI. However, fast leaf trait strategies did prove optimal at dry plots, as carbon losses during the dry season were minimised, whilst photosynthesis during the wet season was maximised. Field estimates showed that leaf NPP was highest at dry plots and declined with increasing precipitation, whilst root NPP was highest at wet plots, converse to optimal partitioning theory, which suggests prioritisation of roots under moisture stress and leaves under light limitation. Yet model results show that leaf:root NPP across the precipitation gradient was optimal, and was similarly best predicted by the maximisation of net canopy carbon export (R2=0.60, p=0.02). Optimality was supported by concurrent shifts in leaf and root traits, which together accounted for 63% of variation in optimal leaf:root NPP. Our findings demonstrate that optimality approaches can be used to successfully predict spatial variation in LAI, leaf:root NPP and leaf traits across an Amazon precipitation gradient. Leaf traits fundamentally shaped modelled optimal responses, ultimately determining carbon assimilation. The response of Amazon forests to increased moisture stress is therefore dependent on the current spatial distribution of leaf traits, their plasticity and the likelihood of future shifts in floristic and functional trait composition. Future work should expand on the findings presented by exploring the responses of carbon allocation and traits to water availability over different timescales.

The effect of increasing green house gases (GHGs) is already changing the worlds climate, increasing atmospheric temperatures and affecting the land-surface, for example, by changing water availability and the viability of crops. These direct and indirect climate change impacts interact with each other, thereby increasing or decreasing the overall impact of a changing climate. South Asia (SA) is a region with complex orography, ranging from high glaciated mountains, the headwaters for large rivers that flow through several countries to feed vast lowland deltas. The region has extensive irrigation systems that support an intensive agricultural industry. These features, together with a highly variable climate, make SA vulnerable to climate change and important for developing understanding of interactions between land-surface climate impacts. This thesis develops simulations to study the interactions between water resources and crop production for SA using a land surface model. Analysis of SA river flows from regional climate model (RCM) simulations indicate an increasing water resource toward 2100. However this RCM does not include abstraction or irrigation. The Joint UK Land Environment Simulator (JULES) represents rivers but irrigation and crops require development to represent key features of the SA crop calendar; these include: the correct growing season inputs for crops, the capability to simulate several crops in rotation during a single growing period (sequential cropping) and crop specific irrigation. This thesis addresses the main development needs for representing the SA region. A method is presented for estimating sowing and harvest dates for SA based on the dominating climatological phenomena, the Asian Summer Monsoon (ASM). This method provides a more accurate alternative to the global datasets of cropping calendars than is currently available and generates more representative inputs for climate impact assessments. In order to model the SA cropping system more accurately, the development and implementation of sequential cropping in JULES with crop specific irrigation is presented to develop simulations to understand how changes in the SA climate could affect water resources and crops. Finally I present simulations in which all of the individual developments from this thesis are brought together; these show the progress that has been made towards simulations that enable analysis of the impacts of climate on rivers, irrigation and crops for SA in a fully integrated way.

Societies in the Maritime Continent depend on monsoon rainfall for their water supply. Large spatio-temporal variability of the rains has a significant socio-economic impact and affects the global circulation. However, the Maritime Continent remains a major modelling challenge. In this thesis, the fidelity of the fifth Coupled Model Intercomparison Project (CMIP5) models at simulating mean climate and its variability over the Maritime Continent is assessed. We find that model horizontal resolution is not a good indicator of performance in atmosphereonly models. Instead, a given model's local Maritime Continent biases are somewhat related to biases in the local Hadley circulation and global monsoon. Cluster analysis on Maritime Continent annual cycle precipitation results in two distinct clusters: Cluster I models are able to capture both the winter monsoon and summer monsoon shift, whereas Cluster II models simulate weaker seasonal migration than observed. A model's Maritime Continent climatological mean-state precipitation is shown to be negatively correlated with sea-surface temperature (SST) biases in central tropical Pacific Ocean (CTPO) and western tropical Indian Ocean (WTIO) regions in coupled CMIP5 models. On interannual timescales, the El Nino-Southern Oscillation (ENSO) and Indian Ocean ˜ Dipole (IOD) teleconnections to Maritime Continent precipitation are well simulated by both uncoupled and coupled CMIP5 models. However, the spatial pattern of these teleconnections is not well captured, especially in coupled models. Idealized Maritime Continent SST-perturbation experiments are performed using the HadGEM3-GA6 atmospheric model in the CPTO and WTIO regions. These result in remote responses of Maritime Continent mean precipitation, somewhat comparable with the signals related to biases found in the CMIP5 coupled models. This suggests that remote Indo-Pacific SST biases in the CMIP5 coupled models could plausibly cause the precipitation biases over the Maritime Continent, and thus highlights the importance of reducing these biases to improve Maritime Continent mean state and climate variability.

The Indian Summer Monsoon, a subsystem of the Asian Monsoon, is one of Earth's most dynamic expressions of oceanic atmospheric-terrestrial processes affecting some of Earth's most densely populated regions. Therefore, it is imperative to have a comprehensive understanding of the Indian Summer Monsoon in order to understand how its behaviour may be manifested by anthropogenic induced climate changes. Reconstructing how the monsoon behaved in the past presents an opportunity to disentangle its sensitivities to a range of forcing parameters (e.g. ice volume) during periods of different climatic states. However, understanding of how the Indian Summer Monsoon behaved in the past has been limited both spatially and temporally, further constrained by discrepancies among climate proxy records. This thesis fills both a temporal and spatial gap in our knowledge of the past behaviour of the Indian Summer Monsoon. High-resolution (millennial scale) records of Indian Summer Monsoon induced river runoff and surface freshening from the core convective region of the Indian Summer Monsoon, the northern Bay of Bengal and Andaman Sea, have been generated from 140 to 70 thousand years ago. These records provide an insight into how the Indian Summer Monsoon responded to the penultimate deglaciation (Termination II), the subsequent warmth of the Last Interglacial Period and ensuing oscillations between warm interstadial and cold stadial periods of Marine Isotope Stage 5. These records are compared with both high-latitude and low-latitude climate records in order to understand how the monsoon responded to changes in Earth's internal climate system and the influence of external forcing.

Climate change is expected to cause changes in the general atmospheric circulation. Particularly important to the global population is an understanding of how weather and climate will change. North Atlantic jet stream changes will drive weather and climate changes, primarily over North-Western Europe, but also over North America, Asia and other parts of the globe. This makes it vital to understand how climate change will affect the jets to determine how the weather and climate will respond. However, the exact nature of the climate change forcings affecting the jet are uncertain. Here, sensitivity studies using a hierarchy of models to determine possible circulation changes due to the thermal forcing of the atmosphere are performed. It is found that the location of forcing, both its latitude-longitude position and its height, has a profound effect on how the circulation responds. A simple mechanistic understanding for shifts and strengthening of the jet through changes in the mean meridional temperature gradients is presented, along with mechanisms for how Hadley circulation changes can affect the jet, and for how tropically forced waves affect the Northern Hemisphere circulation. Important differences between the responses in winter and summer are observed, which can lead to seasonally dependent extreme temperature and precipitation responses. Key forcing locations that force the atmospheric circulation effectively are highlighted. In these locations, the uncertainties in how the forcing due to climate change will manifest must be reduced so that the circulation response can be better quantified. An important uncertainty is how the atmosphere heats up compared to how sea surface temperatures change and connected to this, how the land-sea temperature contrast will respond. As these uncertainties are reduced, the results from these sensitivity studies will provide a guide to understanding how the circulation will change and the associated impacts of the changes.

Investigating past changes in Earth's climate can provide useful information for assessing future climate change scenarios. Planktic foraminifera preserved in marine sediment are commonly used as a tool to reconstruct past environmental change. Here I present a combination of modern census and multinet data from the North Pacific, a new compilation of global census data, a new global calibration for Mg/Ca ratios in Neogloboquadrina pachyderma, and foraminifera assemblage, trace element, and boron isotope data from the North Pacific spanning the last deglaciation. New modern census data from the North Pacific shows that two key sub-polar proxy carrying species, N. pachyderma and Globigerina bulloides, predominantly live between 0-50 m in the water column. Global planktic foraminifera diversity is observed to be driven primarily by sea surface temperature, with upwelling and ocean productivity providing key secondary roles. In the North Pacific, a preservation bias of N. pachyderma over G. bulloides is observed when comparing multinet and core-top samples, highlighting the importance of tracking dissolution during downcore studies. To improve the use of Mg/Ca ratios in N. pachyderma downcore, I produced a new global calibration with a temperature sensitivity of 6 % per °C. This calibration was combined with boron isotope and Mg/Ca data from sediment core MD02-2489 to investigate changes in North Pacific circulation, productivity, and CO₂ during the last deglaciation. Two intervals of high surface CO₂ were observed, the first during Heinrich Stadial 1, where deep ventilation mixed CO₂ and nutrients throughout the water column. The second occurred during the Bølling-Allerød, where stratification pooled nutrients and CO₂ in surface waters, leading to enhanced productivity and CO₂ outgassing. Overall, this thesis improves the use of planktic foraminifera as tools for investigating past climate change and highlights the role of the North Pacific in deglacial CO₂ release.

How are global discourses on climate change negotiated in national policy contexts, and how do they materialise ‘on the ground’, shaping adaptation at a local level? This is the overarching question that this dissertation addresses, as it traces the evolution of climate policy in Malawi since the establishment of an international framework for climate-resilient development in the late 1990s. Drawing on a theoretical framework that combines approaches from Science and Technology, Postcolonial, and Feminist Science Studies, this work spans across international, national and local spaces of knowledge and policy production, revealing the material and often unintended consequences of global scientific constructions of climate change. Fieldwork in Malawi, including interviews with policymakers in Lilongwe and climate-affected communities in Kasache, has revealed tensions at various stages and scales, examined here through a multi-sited ethnographic approach that situates local weather and climate practices in the lineage of colonial and postcolonial narratives and relations. The findings indicate that the discourse on climate change is a mobile, power-laden and socio-cultural practice transversally connecting spatial (international, national, local), historical (colonialism, neoliberalism) and epistemological (élite/subaltern, gender) localities. The exclusion of locally produced knowledge and meanings (by decision makers, farmers, women and elders) from national mainstream adaptation programmes obscures how vulnerability is locally produced, foreclosing opportunities for context-relevant decision-making. While formally increasing women’s participation in local decisional structures, gender and climate change interventions disregard the presence of biophysical and socio-economic factors, including ‘global’ essentialising narratives, which can exacerbate unequal power relations. At the same time, women in Kasache have engaged in collective responses outside international frames of gender empowerment through informal networks that build on historical matrilineal solidarity and democratic participatory practices. Several ‘policy recommendations’ on how to decolonise and democratise climate adaptation interventions can be drawn from the findings of this work. In a nutshell, interventions should be based on the identification of underlying causes of vulnerability and adaptation strategies across societal groups (rather than on homogenous conceptualisations of climate risk exposure) and should acknowledge and address the forms of marginalisation and human agency produced by the discourse of climate-resilient development.

Teleconnections are one of the main sources of intra-annual to inter-decadal variation in weather and climate and are one way that changes at the largest scales can be cascaded to adjustments at the smaller scales. This thesis aims to identify how atmospheric teleconnections might change with a warmer climate. A new method based on point correlation maps and self-organising maps (SOMs) is presented. Proof of concept is demonstrated using 60 years of National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) sea level pressure (SLP) re-analysis data and the medium complexity climate model FORTE (Fast Ocean Rapid Troposphere Experiment). It is shown that the method can identify known teleconnections from historical data and be used to assess how realistically teleconnections are reproduced in a climate model. The method is then applied to an assessment of the capability of three CMIP5 (Climate Model Intercomparison Project 5) models to simulate realistic teleconnections, as a precursor to understanding how teleconnections change with different climate forcings. The three models used are CM5B-LR, GFDL-ESM2G and HadGEM-ES. The performance is variable by region, with each model having different strengths and weaknesses. There are areas where all models perform relatively well, such as the North Atlantic Oscillation, and others where all three models perform badly, such as the Indian monsoon. The teleconnections modelled using historical conditions and under two Representative Concentration Pathways (RCP4.5 and RCP8.5) are compared. There is a lack of agreement between the models as to the changes expected, with few changes being statistically significant. There is no large-scale rearrangement of teleconnections or any new forms of teleconnections in any of the models. Suggested improvements to the method and ideas for further investigation are presented.

The investigation of extreme precipitation events over the western coast of Saudi Arabia is necessary to estimate their potential impact on both socioeconomic activities and the regional environment. The current study aims at understanding the atmospheric dynamics leading to extreme precipitation, to improve weather forecasting in the target region and the development of long-term adaptation policies. Preliminary results reveal that extreme precipitation events in this region occur during the wet season (Nov–Jan). The synoptic mechanisms of these events are a function of the complex interaction between tropical, subtropical and middle-latitude dynamics. The synoptic dynamic processes were identified by a subjective study of the highest 30 extreme events. In addition, the weather circulation patterns (WCPs) of all extreme events were classified objectively by means of an empirical orthogonal function (EOF) analysis based on the mean sea level pressure. WCPs were linked with synoptic dynamic processes and teleconnected with large-scale climate variability modes. Furthermore, WCPs, precipitation and data regarding other atmospheric variables from different regional climate models were used to investigate future changes in extreme precipitation events under climate change. The most important weather circulation patterns, which are associated with extreme precipitation events, were identified. The possibility of extreme precipitation events increases with great uncertainty.

This thesis proposes an innovative model for citation analysis and applies it to 1186 citations derived from twenty papers from one interdisciplinary journal: Global Environmental Change. The main aim of this thesis is to build, not to quantify, a model which facilitates understanding of how citations act, and are acted upon, in citing texts. The model builds on, extends and modifies certain aspects of some existing models on citation form, stance and function. This thesis argues that stance and function are different but related concepts in the analysis of citation. They operate in different directions and, when combined, can reflect the role of citation in the citing text. In order to achieve a fine-grained understanding of the role of citation, citations are analysed within and beyond the level of the statements in which they occur. To achieve this, a new level is proposed for the analysis of citation function: the ‘citation block’. In this thesis, it is argued that citations operate in different directions within and beyond the proposition-level. The current thesis aligns and compares analyses at the clause- and block-levels for every citation. This alignment results in the identification of conventional and unconventional patterns of citing. The model is applied to four sub-corpora of texts from two time periods and representing the more ‘science-like’ and ‘social science-like’ papers in the journal. The text-based analysis demonstrates the complexity of citation practices in interdisciplinary discourse. Overall it is suggested that in this journal the ‘social science’ papers over time have become more similar to the ‘science’ papers. The results also show variation in citation practices between the individual selected papers in each sub-corpus. This variation is attributed to the interdisciplinary nature of GEC. The proposed model has the potential to be used to investigate variation in citation practices beyond interdisciplinary discourse, within and between disciplines or genres.

El Niño Southern Oscillation (ENSO) is the most important interannual mode of climate variability in the tropical Pacific affecting the globe through teleconnections. The evolution of ENSO is studied with focus on individual El Nino (EN) events; factors and processes explaining the behaviours of different EN flavours are identified. The comparison to model simulations reveals a number of biases that explain differences in model behaviour. Based on reanalysis data, ENs are divided into Central Pacific (CPEN), Eastern Pacific (EPEN), and Hybrid (HBEN). ENs are found to form a continuous spectrum of events with CPEN and EPEN as its end members depending on: (1) the Western Pacific subsurface potential temperature anomaly (PTA) about 1 year before the EN peak, and (2) the Western to Central Pacific cumulative zonal wind anomaly (ZWA) between the onset and peak of the EN. Using these two parameters, about 70% of the total variance of the maximum EN SSTA can be explained up to 6 months in advance. ZWA describes the potential for triggering Kelvin waves for a given initial West Pacific recharge state as captured by PTA. A cross-validated statistical model is developed to hindcast the 1980-2016 Nov-Dec-Jan (NDJ) mean Niño3.4 SSTA based on the two parameters. The model is comparable to, or even outperforms, many NOAA Climate Prediction Centre's statistical models during the boreal spring predictability barrier. The explained variance between observed and predicted NDJ Niño3.4 SSTA at a lead-time of 8 months is 57% using five years for cross-validation. Predictive skills are lower after 2000 when the mean climate state is more La Niña-like due to stronger equatorial easterly ZWA caused by an intensification of both, Walker and Hadley cell. The ability of climate models to simulate and predict EN is assessed with data from the Climate Model Inter-comparison Project 5 (CMIP5). Most models are able to capture the main features of different EN types. But models struggle to reproduce large intensity ENs as found in observations. This issue can be traced back to a failure to realistically simulate the oceanic recharged state and the subsequent Kelvin waves for intense EN. Causes of EN involve Kelvin waves that are triggered by westerly wind bursts (WWB). From higher temporal resolution of reanalysis data, WWBs above a certain threshold are required to trigger a Kelvin wave. Kelvin waves are triggered in locations of positive Ocean Heat Content (OHC) anomalies. Intensity, longitudinal coverage and duration of a WWB, the strength of the OHC anomaly and gradient influence the amplitude of Kelvin waves as they propagate. Synoptic pattern analysis suggests that most WWBs are caused by cyclones with the combination of an active Madden-Julian Oscillation. The NorESM is able to reproduce many characteristics of observed WWBs, OHC anomalies and their relation to Kelvin waves. However, differences are noticeable for the distribution of synoptic patterns causing WWBs in the model. In future work, climate models can be used to disentangle causes and effects of EN for correlations identified here with the ultimate goal to advance our understanding of ENSO, its variability and future changes.

The Tana River Basin is one of the most economically-important and ecologically-diverse river basins in Kenya. It contains internationally-recognised biodiversity areas. It is also central to Kenya's future development agenda. However, projected climate change may undermine this agenda and threaten the basin's unique ecosystems. The changing climate, along with issues arising from planned socio-economic development, is likely to increase the existing problems of limited water and land resources. This research projects the impacts of climate change upon three key sectors (water, biodiversity and agriculture) within the Tana River Basin in order to inform national climate change adaptation plans using a range of climate scenarios and models. Once the projected effects of climate change on the three sectors were determined, possible adaptation measures were identified. Then, potential trade-offs or synergies between sectors and adaptation measures were determined. All three sectors are projected to be significantly affected by climate change, even under the lowest levels of warming. Projected increases in precipitation of basin-average of around 12-16% will lead to greater water availability across the basin, but these increases are unlikely to outweigh the increases in water demand caused by the rapidly growing population and industrial development. By contrast, higher temperatures are projected to substantially reduce species richness (of a basin and taxa-average of 30-42% of species at risk of local extinction) and yields of most major crops (including maize, wheat and sugarcane). As climate change is a cross-cutting and multifaceted challenge, results from the individual sectors were combined using GIS and compared to government development plans. Hotspots of projected climate change impacts and development plans were identified in the Upper Tana and Tana Delta regions. This is the first cross-sectoral GIS analysis of the impacts of climate change and development plans in the Tana River Basin and contributes to a greater understanding of impacts and adaptation options in Kenya.

Global temperatures are expected to rise by 2-2.5°C by the middle of the 21st century, posing a significant threat to human populations and the natural environment. Tropical West Africa has been classified as a highly vulnerable region; naturally-driven multi-decadal droughts are predicted to become more frequent and intense 20 years ahead of the global average. Examination of past records of large scale climate change is critical in order to validate climate models and mitigate against future global warming. This thesis examines the land-ocean interactions of a small-scale Western Equatorial African (WEA) river catchment and explores its potential as a record of regional and global climatic change during the Late Quaternary Period. Previous research has documented large-scale WEA climate change using marine cores offshore the Niger and Congo Rivers, however the response of the smaller, medially positioned, Ogooué River catchment remains to be investigated. In 2003, the IMAGES programme recovered 34 m of sediment, spanning the last 150 ka, from the Ogooué Fan, offshore Gabon. Geochemical, sedimentological, isotopic (δ¹⁸O and δ¹³C), trace element and palynological analyses were carried out. Three research objectives were established: (1) reconstruct the hydrological variability of the Ogooué River catchment through the identification of terrigenous fluvial discharge events; (2) explore the glacial and interglacial control of surface and bottom water δ¹³C in the Eastern Equatorial Atlantic (EEA); and (3) examine WEA vegetation biome changes in order to infer the drivers of past regional hydrological and climatic change. Sedimentological and geochemical investigations demonstrated the strong potential of using a Fe/Ti ratio and foraminiferal planktic δ¹⁸O as proxies for Ogooué River discharge variability. Ogooué discharge events were synchronous with the neighbouring Sanaga and Congo Rivers and were also concomitant with precessional maxima. A preliminary sea surface temperature (SST) reconstruction evidenced coeval SST and salinity responses to riverine discharge variability and highlights an opportunity to undertake further trace element analysis on the study material. Planktic and benthic δ¹³C stratigraphies were constructed in order to produce the first Δδ¹³C gradient record from a region of EEA not dominated by upwelling. Thermocline - bottom water Δδ¹³C evidenced an alternation of nutrient-poor North Atlantic Deep Water influx during glacial periods and nutrient-rich Antarctic Intermediate Water masses during interglacial periods. Locally, planktic d18O data support that precessionally driven riverine discharge events contributed to the δ¹³C of the planktic foraminifera Globigerinoides ruber (white variety). Finally, vegetation change in the Ogooué River catchment, and wider WEA, was documented through palynomorph reconstructions. Pollen data evidences a transition from grassland vegetation in glacial marine isotope stage (MIS) 6, through to more precipitation dependent lowland rainforest and swamp biomes from interglacial MIS 5 (~ 100 ka) to present day. High abundances of rainforest taxa in MIS 4-2 suggests rainforests remained as refugia facilitated by a weaker monsoon. The mangrove pollen, Rhizophora, is interpreted as an indicator of sea level change, with high abundances in MIS 5 and 1 evidencing sea level rise. Lastly, the Afromontane pollen Podocarpus, shows a strong correspondence with precession minima, suggesting alternating dominance of trade wind and monsoon intensity over the 23 ka precessional cycle.

This thesis explores how δ18O values in horse hair relate to local meteorological observations; how Greenland ice core records relate to European terrestrial climate records; and how atmospheric changes are reflected in terrestrial and biological records. Bringing together analysis of increasingly complex palaeoenvironmental proxies, δ18O measurements within atmospheric, terrestrial and biological systems are critically assessed across geographical transitions, ultimately leading to greater understanding of the utilisation of oxygen isotope data for seasonal climate analysis. Horse hair sampling and δ18O analysis were conducted on horse hair from: the Icelandic Food and Veterinary Authority (MAST) in Selfoss, Iceland; the Thordale Stud in the Shetland Islands, United Kingdom; the Exmoor Pony Centre (EPC) in Somerset, UK; and the Pigeon House Equestrian centre in Oxfordshire, UK. The North Greenland Ice Core (NGRIP2) was sampled and analysed for δ18O, and compared to a master tree ring dataset of compiled δ18O values in the UK. The results confirm that rainfall quantity and continental effects dominate both the horse hair and ice core δ18O records. The growth rates of the hair were seen to decrease with an increase in latitude; and comparison between horse hair δ18O and meteorological variables clearly indicates a rainfall influence. Comparison between the ice core δ18O and historical coastal temperature reconstruction shows a similar gradient to what is seen in modern temperature records. The comparison between tree ring isotopes can be interpreted as showing a similar amplitude to the historic temperatures, but with a slight dampening in regards to lower peaks values. Comparison of the tree ring and ice core values indicated a significant negative correlation, with smaller amplitude changes within the tree ring δ18O results. Wavelet analysis suggested a common influence from teleconnections at several timescales in both the tree ring and ice core datasets, including the El Niño Southern Oscillation and the North Atlantic Oscillation. This study demonstrates that geographical and meteorological influences are similarly reflected within palaeoenvironmental proxies of increasing complexities. It also identifies periods of common influence from climate drivers and provides detail of the greatest effects on isotopic variation in the UK, Iceland and Greenland.

Global climate change will likely alter rainfall at a regional scale. This is a particular concern in southern Africa, where rainfall is central to socioeconomic wellbeing and where we do not understand the full complexity of the climate system. Climate models are the only tools available to estimate future rainfall change, but in the southern African summer rainfall season the latest generation of general circulation models disagree on the sign and magnitude of this change. Some models project small increases in rainfall (~20 mm.season-1) while other simulate large decreases (~100 mm.season-1), and this diversity occurs in the context of large positive rainfall biases (up to 300%) in the present day. Regional policymakers are thus left with the task of designing strategies for climate change adaptation across a wide range of possible futures. With a view to assessing model reliability, this thesis addresses this problem by investigating the physical processes which underlie present day rainfall biases over southern Africa, and which explain the range in future rainfall projections. In tropical and eastern regions of southern Africa, present day intermodel variability in the strength of an important regional circulation feature, the Angola Low, accounts for 40 to 60% of intermodel rainfall variability. Meanwhile, in the subtropical region, intermodel variability in the strength of anomalous northeasterlies across the high topography of Tanzania and Malawi explains 72% of the intermodel spread in rainfall. These findings suggest that improving the representation of the Angola Low, topography and the northeasterly flow should be targets for model development. In the future projections, the model diversity in rainfall response is associated with differences in the large scale adjustment of the tropical atmosphere to warming. In models projecting the highest magnitude drying, the northern tropical oceans warm at a faster rate than the tropical mean (+0.5 K), and this is associated with enhanced subsidence and greater atmospheric stability over southern Africa. However, the most severe projections of drying (>60 mm.season-1) only occur in models with large biases in the present day circulation, tropical sea-surface temperatures, topography and rainfall. The thesis therefore suggests that extreme drying is an unlikely scenario.

The Northern Isles are strongly influenced by changes in the North Atlantic Ocean atmosphere system and, as they project northwards from the British Isles, provide an ideal geographical opportunity to study changing climatic gradients during the last glacial/interglacial transition along with the detection of regime shifts. Three proxies, diatoms, pollen, and micro-XRF sediment chemistry, have been employed to explore the nature and timing of environmental changes within the water columns and the wider catchments of Loch of Sabiston, Orkney, and Loch of Clumlie and Loch of Grimsetter, Shetland to better understand the nature and timing of environmental change within and among the island groups. The records are constrained by radiocarbon dating, supported by tephrochronology, and the Greenland ice core chronology to enable the comparison of the records produced by this study with previous research in the North Atlantic region. The diatom and lithological results from Loch of Sabiston suggest early deglaciation at c. 23,000 cal BP followed by gradual warming (GI-1e) punctuated by the cooling events coeval with GS-1 and GI-1b. However, the pollen record reflects a lagged response in the development from colonising cold tolerant vegetation to more temperate shrub and woodland communities. The Oracadian signal is dominated by the switching on and off of the accumulation of marl which serves as a supporting indicator of warmer conditions. The Shetland landscape appears to have been deglaciated later at c. 16,400 cal BP, but also has clear representation of GI-1e and the cooling events of GI-1b and GS-1. Both the Shetland and Orkney records record the dramatic cooling of the Younger Dryas but also suggest a two stage change from colder and drier to colder and wetter conditions before the onset of the Holocene. Shetland appears to have experienced less extreme climatic changes in comparison to Orkney despite being in the same present phytogeographical region. This is likely due to the former persisting in the arctic domain and the latter being closer to the latitudinal shifts in the warmer ocean circulation of the North Atlantic during the LGIT. Comparison of the three proxies demonstrates that they may differ by several hundred years in their response to dramatic climatic changes and, therefore, highlights the strength of multi-proxy approaches to reconstructing Quaternary environments. Combining proxies such as diatom and μ-XRF scanning techniques will provide a greater understanding of the processes occurring during environmental change in this region.

The study of past climates provides a unique opportunity to test our understanding of the Earth system and our confidence in climate models. The nature of this subject requires a fine balance between complexity and efficiency. While comprehensive models can capture the system’s behaviour more realistically, fast but less accurate models are capable of integrating on the long timescale associated with Palaeoclimatology. In this thesis, a statistical approach is proposed to address the limitation of our simple atmospheric module in simulating glacial climates by incorporating a statistical surrogate of a general circulation model of the atmosphere into our Earth system modelling framework, GENIE. To utilise the available model spectrum of different complexities, a multi-level Gaussian Process (GP) emulation technique is proposed to established the link between a computationally expensive atmospheric model, PLASIM (Planet Simulator), and a cheaper model, EMBM (energy-moisture balance model). The method is first demonstrated by emulating a scalar summary quantity. A dimensional reduction technique is then introduced, allowing the high-dimensional model outputs to be emulated as functions of high-dimensional boundary forcing inputs. Even though the two atmospheric models chosen are structurally unrelated, GP emulators of PLASIM atmospheric variables are successfully constructed using EMBM as a fast approximation. With the extra information gained from the cheap model, the emulators of PLASIM’s 2-D surface output fields, are built at a reduced computational cost. The emulated quantities are validated against simulated values, showing that the ensemble-wide behaviour of the spatial fields is well captured. Finally, the emulator of PLASIM’s wind field is incorporated into GENIE, providing an interactive statistical wind field which responds to changes in the bound- ary condition described by the ocean module. While exhibiting certain limitation due to the structural bias in PLASIM’s wind, the new hybrid model introduces additional variations to the over-diffusive spatial outputs of EMBM without incurring a substantial computational cost.

The mid- to late Miocene marks one of the last warm periods of the Neogene, before the descent in to the ice house climate of the late Pliocene and Pleistocene. The mid- to late Miocene climate was long overlooked, but receives increasingly more interest. This study used organic geochemical biomarker distributions and their isotopic signatures in sediment samples from the Japan Sea, recovered during IODP Expedition 346 and ODP Leg 127/128. It was the aim to reconstruct paleoceanographic and paleoclimatic changes over the last 18 Ma. Reconstructed sea surface temperatures revealed declining temperatures since the Mid-Miocene Climatic Optimum, possibly driven by a long-term decline in atmospheric CO2. Reconstructed pCO2 using alkenone paleobarometry, revealed a late Miocene decline from circa 520 μatm to 380 μatm. A decline in this range is required to trigger the onset of the late Miocene C4 plant expansion, which was also fully detected in the sedimentary record from the Japan Sea. Stable isotope analysis of n-alkanes (δD and δ13C) revealed an intensified summer monsoon from 5-3 Ma, which also led to a freshening of surface waters in the Japan Sea. Overall, the Japan Sea is a suitable study area for the late Miocene climate change.

This thesis presents new micro palaeontological and geochemical palaenvironmental proxy data through the late Eocene into the earliest Oligocene from a clay-rich succession from the US Gulf Coast. It is based on samples from the Yazoo Clay Formation, recovered in the Mossy Grove Core near Jackson, Mississippi. This represents an apparently continuous section of relatively uniform lithology, clay-rich deposits that host very well preserved assemblages of calcareous nannofossils, foraminifera and organic biomarkers. This thesis makes use of these to generate a detailed calcareous nannofossil taxonomy, high-resolution calcareous nannofossil assemblage data and coccolith-fraction bulk isotope data, as well as pilot planktonic foraminifera abundance and isotope records. It also develops pilot data for organic biomarkers that demonstrate the presence and utility of biomarker proxies for ancient sea surface temperatures within the Yazoo Clay. The results of this project characterize the late Eocene US Gulf Coast as a sub-tropical shelf sea environment that experiences several stages of sea surface cooling and increasing nutrient contents - potentially linked to sea level fall - in the late Eocene and earliest Oligocene. The most important finding of this project is evidence for cooling and major perturbations to the climate-carbon cycle significantly before the onset of the major phases of Antarctic glaciation.

The timing of glacial-interglacial cycles shows a clear dependence on the periodic variations in the Earth’s orbital parameters. However, the Earth’s climate is an extremely complex, non-linear system, with many internal feedback mechanisms and there are still features of the climate record for which a definitive explanation remains elusive. Understanding reef history is important due to significant predicted feedbacks between changes in global climate and carbonate production via the carbon cycle; phases of rapid reef growth in shallow water areas being associated with increased release of carbon dioxide to the atmosphere. Previous work on Pleistocene reef history, investigated via reef boreholes, shows a large global expansion of reefs between 800-400ka; approximately concurrent with one of the major unexplained alterations in the climate system, the Mid-Pleistocene Transition (MPT). Quaternary reef history is usually investigated via reef boreholes, which provide limited spatial information and are subject to dating uncertainties of the order of ±100kyrs. This means that any inferences made about the relationship between reef expansion and specific changes in the climate system are not well constrained. This thesis instead, presents a novel approach to reconstructing reef growth history, using a trial site near the island of New Caledonia, in the south west Pacific. The initiation of carbonate production on shallow shelves is known to produce a signal in the surrounding deeper basins, via sediment shedding. Therefore, this research set out to independently verify the proposed expansion of the New Caledonia Barrier Reef at ~ 400ka (Marine Isotope Stage [MIS] 11) by examining the composition of turbidites deposited in the New Caledonia Trough. Deep sea sediment core MD06-3019, was collected south west of the New Caledonia Barrier Reef (22oS, 165oE; 3,500m water depth). It is predominantly composed of pelagic carbonate ooze, into which 79 sandy turbidite layers have been deposited. These layers interrupt, but do not disturb, the background sedimentation and source material from the shallow shelf, which is carried to the deep sea via submarine canyons. A core age model based principally on orbital tuning, yields a core bottom age of 1,260ka, ~MIS38. This chronology has allowed the timing of deposition of the turbidite layers within the core to be assigned to within ±10kyr. Turbidite layers vary in width (1-35cm), grain size (φ=4 to -2) and composition, containing among other shelf derived material, well preserved coral fragments from 1.26Ma through to the present day. Patterns in turbidite timing and frequency, grain size and composition (investigated via point counting, carbonate coulometry and aragonite content) have been analysed, to assess whether there are any temporal changes which may reflect variation in shallow shelf reef extent. This included the development of XRF scanning measurements for [Sr], as a new proxy for the aragonite content of samples. A calibration line with the equation: Aragonite %=0.0011* Sr count +2.64 (R2 =0.6105, p-value < 0.001) was obtained for turbidite samples from sediment core MD06-3019. The method shows significant promise as a new proxy for quickly establishing the aragonite content of sediment samples. Corroborating the work of previous investigators, turbidites deposited since MIS11 show an increase in average bulk carbonate and aragonite content, a greater dominance of shallow water bioclasts and a higher occurrence of coral fragments. Additionally, both coarse and fine grained turbidites are present, whereas directly before this period only fine grained turbidites occur. However, there is another significant shift in depositional style further back in the record. Prior to MIS23 both coarse and fine grained turbidites are present, the average carbonate content of turbidite layers is higher and there is a greater dominance of shallow water biota. Coral abundance for turbidites at the base of the core can equal values for turbidites at the top of the core. These results challenge the assumption that the only significant evolution on the western New Caledonia margin over the last 1.2Myrs was the expansion of the barrier reef at MIS11. This suggests that the history of the western New Caledonia margin may be more complicated than initially anticipated. These temporal variations in turbidite deposition are interpreted as reflecting changes in the level of carbonate production on the shallow shelf over the course of the 1.26Myr record. Shallow water carbonate production having decreased substantially during the period MIS23-MIS11. There are many possible controls on the shallow water carbonate production; such as: sea surface temperature and salinity, sea-level and nutrient availability. However, it is hypothesised that the principal control is glacial-interglacial sea-level change. It is proposed that prior to MIS23 sea-level was high enough during certain interglacial periods for significant carbonate production to occur on the shelf. However, from MIS23 onwards the climate proceeded into a period of ‘lukewarm’ interglacials which were both cooler and had lower sea-levels. It is hypothesised that during this period sea-level did not rise enough during highstands to flood the shelf sufficiently to allow for significant shallow water carbonate production. The high sea-levels of the long, warm MIS11then allowed for the expansion of the barrier reef (perhaps on substrates provided by former siliciclastic coast lines, deposited between MIS23-11) and its continuation during subsequent interglacial periods until the current day. This pattern of shallow shelf carbonate production is similar to those proposed for the Belize margin and the Gulf of Papua over the last 1.2Myrs. This thesis provides one of the first detailed investigations of gravity deposits in the New Caledonia Trough, providing information on their composition and timing over an unprecedented 1.26Myr time period. This study demonstrates that deep sea turbidites, sourced from shallow shelf areas, can be used to help reconstruct tropical reef growth histories. The results corroborate the work of previous researchers in the area and provide new insights into the history of reefs along the western New Caledonian margin. The main advantage of this method, compared to traditional borehole techniques, is the 10-fold reduction in the age uncertainty of events, to ±10 kyr. In addition, because turbidite material is sourced from a wide area along the coast, the method is able to provide information on reef history over a larger spatial area than single reef boreholes. This method can now be extended globally to help improve knowledge of the timing and history of tropical reef growth during the Quaternary. This will enable a better understanding of how reefs have impacted on, and been affected by, changes in climate, linked by feedbacks mechanisms via the global carbon cycle.

The aims of this research were to firstly help development of clumped isotope measurements of carbonate samples at UEA, and to then explore whether the technique could be used to retrieve robust environmental signals from geological material. This specifically looks at the Hirnantian glaciation at the boundary between the Ordovician and Silurian periods. Using the MIRA instrument, it is possible to make high precision measurements to enable the assessment of Earth surface temperatures. Long term precision of standard material is comparable to existing studies. MIRA is also absent of any non-linearity issues. Removal of contaminants and the identification of samples displaying contamination is stringent, as we find contamination has a serious effect on the Δ47 signal. Using modern biogenic carbonates and controlled temperature precipitates, the relationship between the clumped isotope signatures represented by the Δ47 value and temperature is: Δ47(ARF) = 3.5 x 10⁴/ T² + 0.2416. The relationship lies within measurement error of the theoretical estimate of temperature sensitivity. Applying this temperature calibration to fossil material collected from across the Ordovician/Silurian boundary found that the clumped isotope signal had been overprinted during diagenesis, and it has not been possible to extract an original Earth Surface temperature. However, the isotopic signal does show how the basin has developed during diagenesis under closed system conditions. As a result, the bulk δ¹⁸O and δ¹³C values have not been altered and record an original environmental signal.

Grounded in a methodology of critical discourse analysis and semi-structured interviews, this thesis investigates constructions of racial and national identities in US and EU climate security discourses. Utilizing a theoretical framework based on ‘essentializing logics’ (a concept developed to analyze how naturalized assumptions and associations about populations are held in relation to possible climate-insecure futures), the thesis argues that intersectional racial and national identities are constructed in context-specific moments of US and EU climate security discourses and are underpinned by multiple biopolitics of unequally valued lives. This argument is elaborated in three empirical chapters. First, the thesis examines the racialization of ‘Muslim’ and ‘African’ climate-induced migrant populations in particular, situated moments of climate security discourse. The second empirical chapter focuses on discursive representations of interconnections between climate change and terrorism and how such interconnections represent important points of intersection for racial and national identities in climate security. The final empirical chapter examines representations of American nationhood in US climate security discourse. These include constructions of American exceptionalism, the impacts of Hurricane Katrina and Hurricane Sandy for conceptions of American national identity, and the development of ‘climate-resilient’ American nationhood. The thesis concludes by reflecting on the project’s findings. I argue that multi-scalar interpretations of environmental justice (grounded in a manifesto for ‘abundant futures’ (Collard et al (2015)) and Koopman’s (2011) feminist ‘alter-geopolitics’) could provide a tentative means through which to think about more just, situated environmental securities.

Peatlands store ~30% of global soil organic carbon (SOC) and are frequently carbon dioxide (CO2) sinks, while also being sources of methane (CH4) due to anaerobic decomposition under waterlogged soil conditions. Hence, the role of peatlands in the radiative forcing of the Earth’s atmospheric system and their impact on the global climate system is complex. This study presents the first long-term direct flux measurements of land-atmosphere CO2 and CH4 exchange at a temperate lowland fen peatland in East Anglia, UK. The dynamics and magnitude of CO2, H2O, CH4 and energy fluxes were quantified using the eddy covariance (EC) technique at two sites: a former-arable regenerating site (Baker’s Fen, BF) and a semi-natural fen (Sedge Fen, SF) at Wicken Fen NNR. This allowed investigation and comparison of ecosystem responses to climate variability and restoration. EC measurements at BF covered three annual cycles (2013 - 2015), and at SF two and a half cycles (August 2013 - December 2015). BF acted as a net CO2 source in all years, emitting 161.03±12.51, 83.61±11.53 and 98.39±13.31 g CO2-C m-2yr-1 in 2013, 2014 and 2015, respectively; it was a net CH4 source of 6.067±0.096 g CH4-C m-2yr-1 in 2013 and 2.009±0.087 g CH4-C m-2yr-1 in 2015, and of 2.845±0.103 g CH4-C m-2 (8th April - 31st December 2014). The annual carbon balance for BF was lower than average carbon losses from arable fens, indicating that restoration can achieve net carbon emissions reduction. SF was also a net CO2 source of 297.59±9.16 g CO2-C m-2 (1st August - 31st December 2013), and a large net CO2 sink of -356.86±49.13 g CO2-C m-2yr-1 in 2014 and of -243.78±15.25 g CO2-C m-2yr-1 in 2015. Large inter-annual variability in CO2 exchange at SF indicates sensitivity to climatic conditions, and highlights the need to maintain an appropriate water level height to prevent or reduce soil carbon losses to the atmosphere as CO2.

This thesis examines the relationship between synoptic meteorology and particulate matter (PM10). PM10 is a pollutant of high interest to UK health policy (DEFRA, 2016) and this study evaluates the importance of Rossby wave breaking (RWB) on UK PM10 concentration ([PM10]). RWB can result in atmospheric blocking, which is one extreme of mid-latitude synoptic meteorological variability that favours the accumulation of PM10. This study finds significant increases (p < 0.01) in UK Midlands [PM10] resulting from winter-time northeast Atlantic/ European RWB. Furthermore, this study shows that northeast Atlantic/ European RWB increases the probability of exceeding a hazardous [PM10] threshold. We have identified the Omega block as the most hazardous RWB subset, with a probability of exceeding a hazardous [PM10] threshold (0.383) over three times that for days without RWB (0.129). We have implemented a tracer framework within a Hadley centre Met-Office climate model (HADGEM3-GA4) to identify flow regimes influencing the UK throughout northeast Atlantic/European RWB events. A present-day HADGEM3-GA4 simulation, nudged to ERA-Interim reanalysis data, is used to verify the tracer framework and to identify the flow regimes influencing Omega block events. This study finds that the advection of European tracer and the accumulation of locally sourced tracer contribute to hazardous [PM10] throughout Omega block events. This study’s principal aim is to determine climatic shifts in both the frequency of synoptic meteorological conditions conducive to UK PM10 accumulation and in the corresponding flow regimes. Using a further two HADGEM3-GA4 simulations, we find a north-eastward climate shift in northeast Atlantic/European RWB, with an overall reduction in events. Additionally, we find that uture RWB events result in significantly (p<0.01) increased European and reduced stagnant air masses within the UK. This result indicates a reduced frequency of UK [PM10] exceedances, however a tendency for increased transport of toxic particles from Europe.

Outcrops of late Quaternary deposits along the north–east coast of Mallorca were examined, and a high resolution chronological framework established using optically stimulated luminescence of quartz and feldspar grains. Coastal sections at Es Barrancar and Cala Mata record a complex succession of alluvial fan deposition with a minor aeolian component, mainly deposited during the last two glacial cycles. For the last ~200ka different orbital configurations appear to have produced a series of subtly different climatic scenarios that resulted in great variations in the regional availability of moisture. In turn, each of these climatic scenarios set in motion a distinct set of sedimentary processes, which imprinted themselves upon the character of fluvial system response recorded in the alluvial archives on Mallorca. Within the resulting complex of sediments were units of fluvially reworked aeolianite which, although truncated in places, were traceable laterally along wide sections of the sea front outcrops of both fan systems. These archives yielded 47 new OSL and pIRIR290 ages which suggest a number of previously unrecognised periods of enhanced fluvial activity. Luminescence ages identify significant ephemeral fluvial activity taking place during MIS 6, MIS 5 sub-stages d/c, b/a, and across the MIS 5/4 boundary. Another major phase of reworking corresponds with the middle part of MIS 3, and continued sporadically into the Last Glacial Maximum. These fluvial reworking events have been interpreted as having taken place during cold arid climatic intervals, when vegetation was at a minimum, precipitation was low and displayed a much higher degree of seasonality, enhancing the effects of runoff.

Data assimilation (DA) is an emerging research area in palaeoclimatology. Here, ensemble-based DA schemes are implemented and evaluated for the reconstruction of the climate of some of the key periods from the past millennium. The study is among the first to employ a General Circulation Model for palaeoclimate DA. An off-line and an on-line DA method are first compared, assimilating continental proxy-based temperature reconstructions and using the 17th century as testing period. Both schemes provide simulations that follow the assimilated targets on large scales better than without DA. The on-line scheme has the advantage of temporal consistency of the analysis, and is subsequently used to reconstruct the climate for 1750-1850 AD. The assimilation performs well on large-scale temperatures, but there is no agreement between the DA analysis and reconstructions for regional temperature patterns. Evidence is presented to suggest that this lack of information propagation to smaller spatial scales is likely due to the fact that the Northern Hemisphere continental mean temperatures are not the best predictors for large-scale circulation anomalies, or that the assimilated reconstructions include noise. The lack of regional skill is again found when instrumental data for 1850-1949 AD are assimilated. Based on these results, it is argued that a potential way of improving the performance of DA is the assimilation of temperature reconstructions with higher spatial resolution.

There is strong scientific consensus on the evidence of anthropogenic climate change which will increasingly present social, economic and institutional challenges. The Fifth Assessment report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) established that ‘human influence on the climate system is clear’ and that ‘changes in many extreme weather and climate events have been observed since about 1950’ (IPCC 2014a). Associated impacts include sea level rise and increased likelihood of extreme weather worldwide such extreme rainfall, heat waves, hurricanes and tornados (IPCC 2014a; Klijn et al. 2015). Climate change adaptation is the adjustment in natural or human systems in response to actual or expected climatic stimuli or their effects in order to minimise the impacts and to take advantage of new opportunities (IPCC 2007). Many vulnerable countries, regions and cities have accepted that some form of adaptation is inevitable (Swart et al. 2014). This thesis contributes to the research on decision-making for climate change adaptation in order to reduce vulnerability. Both bottom-up and top-down analyses are applied to complement one another with an application to flooding. Flood risk is expected to increase in the UK under climate change (Alfieri et al. 2016; Scottish Government 2016) associated significant economic damage (CEA 2007). From a top-down perspective, the thesis explores how to enhance economic decision-making under climate change uncertainty. In a situation of uncertainty the costs may be clear and immediate whereas the benefits are uncertain and often only realised in the distant future. This impedes the use of standard decision-making tools such as cost-benefit analysis that rely on the quantification of (expected) costs and benefits. The thesis begins on the macro scale with a taxonomy of economic decision-making tools for climate change adaptation, discusses the sector level and subsequently proceeds to the case study micro-scale with applications of adaptation decision-making. First, the potential of alternative decision-making tools, so-called robust decision-making approaches, is examined. The strengths and weaknesses of these tools relative to traditional decision-making processes such as CBA are explored and their future potential in the adaptation process evaluated. It is found that robust decision-making tools under uncertainty provide performance across a range of climate change scenarios, but they may yield lower overall performance if compared with the alternative strategy under the actual climate outturn. Furthermore, they are resource intense and decision makers need to balance the resources required for employing the methods with the added value they can offer. A flow-chart is developed to provide guidance on which decision-making tool should be applied depending on the scale and type of adaptation project. On the sector level, the economic appraisal of adaptation options for agriculture is explored. Agriculture is particularly vulnerable to climate change due to the direct impacts of weather and climate on agricultural output and the sector plays an indispensable role in providing (and improving) food security as well as creating employment. Many of the adaptation options in agriculture involve short-term managerial changes and can be appraised with standard economic decision-making and the options can be carried out after the climate signal has been observed. For those adaptations that do require a longer time to take effect or are long-lived and are (partly) irreversible in nature, robust approaches have a valuable role to play in decision-making. Suggestions are made regarding how robust decisionmaking tools under uncertainty can be practically applied to adaptations in agriculture, outlining the data needs and the steps of the data analysis for three different applications. On the micro level, for a case study in the Eddleston Water catchment in the Scottish borders, UK, two different economic appraisal tools are applied. These include a cost-benefit analysis of afforestation as a flood management measure under different climate change scenarios which can provide important insights for adaptation decisions when robust decision-making tools under uncertainty are not feasible due to resource constraints. It is found that the flood risk under climate change increases substantially in the case study area which needs to be taken into consideration for economic appraisal. The results of the CBA reveal that all modelled scenarios of afforestation have positive NPVs which are driven by further eco-system services (including climate regulation, water quality and recreation) rather than flood regulation benefits. It is concluded that eco-system services beyond flood regulation should be considered for the appraisal of NFM to enable policy-makers to make informed decisions. Second, the Expected values can be used in situations of quantifiable uncertainty, i.e risk. But for climate change we do not have a strong methodology to assess these subjective probabilities. They cannot be fully based on the past, because climate change is a new process for which we have no historical equivalent. Models share common flaws in their assumptions and their dispersion in results cannot be used to assess the real uncertainty (Hallegatte, 2012). The term deep uncertainty (Lempert et al., 2003) or severe uncertainty is used (Ben-Haim, 2006) in these contexts. Such uncertainty is characterised as a condition where decision makers do not know or cannot agree upon a model that adequately describes cause and effect or its key parameters (Walker et al., 2012). This leads to a situation where it is not possible to say with confidence whether one future state of the world is more plausible than another. The robust decision-making tool under uncertainty real option analysis is applied to the same case study to allow for adjusting adaptation options over time by integrating lessons learned about climate change in the appraisal process. A simplified ROA is presented to minimise the life cycle cost of a system that aims to prevent flooding of a return period of 1/20 using tools which should be available to most public authorities. This includes the use of UKCP09 climate data, analysis of changes of peak flow under the measure implemented, cost structures for the measure and damage cost under different outcomes. The analysis can be carried out in an excel spread sheet with the aforementioned types of input. The results of the analysis demonstrate that the obtained strategy is significantly cheaper than planting for the worst case scenario and presents the potential for learning under climate change uncertainty as a way to allocate resources in a more efficient way. The complementing bottom up approach investigates behavioural barriers to decisionmaking for adaptation. Standard economic theory tells us that self-interest will motivate most actors to engage in efficient private adaptation as long as the costs do not exceed the benefits. Thus, we would expect households at flood risk to invest in flood adaptation measures. However, it has been observed that households do not necessarily take action to protect themselves and their assets from flooding. In a study carried out in co-operation with 36 communities around Scotland, protection motivation theory is used to explain the uptake of household flood protection and whether community led flood action groups can increase uptake. It is found that flood action groups directly and indirectly influence the uptake of some flood protection measures positively in particular if tailored information is provided. Overall, it is concluded that both top-down and bottom-up approaches play an important role to move towards an economically efficient adaptation in the context of flooding., From a top-down perspective, uncertainty should be explicitly acknowledged and included in economic decision-making for adaptation (to flooding) to make an informed decision. The type of analysis will depend on the adaptation project and resources at hand. Developing and fostering bottom-up tools such as flood action groups to increase the uptake of the type of household flood protection with a benefit-cost ratio above 1 may also contribute towards the more efficient allocation of resources.

This thesis presents an empirical study of dendroclimatology, with the purpose of contributing to a wider understanding of the way scientists generate knowledge about climate change. Dendroclimatology is a science that produces knowledge about past climates from the analysis of tree growth. For two years, I have studied the work of a group of dendroclimatologists, joining them on fieldwork and sampling expeditions in the Scottish Highlands, observing how they generate data from tree samples to reconstruct past temperatures in Scotland and examining how they have mobilised a Scottish temperature reconstruction in a scientific debate over historical changes in climate. This thesis develops two parallel narratives about the practice of making dendroclimatological knowledge and the roles of trust and scepticism in this process. In describing how dendroclimatologists work to extract information about past climates from trees, I identify the importance of trust relationships and scepticism at each stage of their work. I conduct a symmetrical analysis of both trust and scepticism in science. In the past, scholars studying science have emphasised the critical role of either trust or scepticism in the construction of scientific knowledge, and have paid relatively little attention to examining the relationship between the two. In my study, I demonstrate that scepticism is part of the ordinary practice of dendroclimatology, and that scepticism in normal science (which I call “civil scepticism”) is fundamentally dependent (or “parasitic”) on existing trust relationships established through a variety of means. Dendroclimatologists engage in intimate interactions and mutual scrutiny of each other’s competence throughout the work they do in the field and in the laboratory, and they build upon and expand these trust relationships to create and defend climate reconstructions. I show that dendroclimatologists sustain trust relationships in part by demonstrating that they are competent sceptics (which I call “sceptical display”) and, in part by provisionally suspending their scepticism to permit agreement on what constitutes valid dendroclimatological knowledge. I also analyse how these internal practices of scepticism and agreement are influenced by sceptical challenges from actors external to the dendroclimatology community, including challenges grounded in similar trust relationships (a further instance of civil scepticism) and challenges that are not (which I call “uncivil scepticism”). I conclude that dendroclimatological knowledge is only possible as a result of contingent social negotiations over the distribution of trust and the boundaries of a trusting community.

The reliable prediction of the future climate change requires high-quality densely distributed climate records that clarify natural climate variability and its recent modulation by anthropogenic impacts. Stalagmites can meet those requirements; however, conservation concerns require new non-destructive techniques to preserve the natural environment of the caves. This thesis discusses two high-resolution Holocene climate reconstructions built using i) geochemical analyses of a Bermudan stalagmite and ii) novel and non-destructive Computed Tomography data from a Spanish stalagmite, as well as iii) supporting cave monitoring data. Considered together, these efforts provide a complementary view of diverse aspects of climate change across the North Atlantic, and provide insights into how anthropogenic CO2 emissions may further affect climate. Monitoring of environmental conditions took place at Leamington Cave (Bermuda) and Conch Bar Caves (Turks and Caicos Islands). To our knowledge, these are the first long-term monitoring efforts at coastal sites near sea level. The results of continuous monitoring of these two near shore caves in the tropical western North Atlantic are not dissimilar to previous results derived from inland caves. The microclimate and ventilation dynamics of Leamington Cave and Conch Bar Caves are controlled mainly by seasonal temperature differences between outside and cave air, wind, and rainfall totals. However, because hydrological connections with the sea, the microclimate of these near shore caves is also modulated by the seawater temperature, and sea level fluctuations. Following from the cave monitoring efforts, one stalagmite from Leamington Cave was collected. The 18O of stalagmite BER-SWI-13 provides an annually-resolved rainfall record for the last 700 years. The record suggests that the tropical cyclone activity in Bermuda following the Industrial Revolution has not exceeded its longer-term natural variability. Higher tropical cyclone activity during Bermuda’s pre-colonisation period is associated with more El Niño events and positive NAO phase and reflects the northeast-ward tropical cyclone tracks migration that coincides with the low TC activity in the Caribbean Sea. Finally, one stalagmite from southern Spain was used in a pilot study to assess the applicability of CT scanning to speleothem-based climate reconstruction. Internal density variability of stalagmite REF-07 (from Refugio Cave) was used to create a time-series record of stalagmite density, which was then linked to climate. The record reveals Holocene climate variability in southern Iberia, and suggests that the current Mediterranean climate in southern Iberia was initially emplaced at approximately 5.3 ka BP following gradual southward migration of the North Atlantic Subtropical High.

Climate exerts a profound control on the processes that shape landscapes and produce the sedimentary deposits with which we can interpret the Earth's history. However, we lack a complete understanding of how sensitive tectonically-active, eroding landscapes are to climate and climate change. How does a simple sediment routing system react to a change in rainfall rate? Can mountainous landscapes respond quickly enough to preserve a record of high-frequency climate changes, e.g., glacial-interglacial cycles? What effect does headwater glaciation have on downstream sediment characteristics? Can we quantify past climate changes using the sedimentological properties of terrestrial stratigraphy? Geologists lack complete answers to these questions, among many others. Theoretical work, using physical first principles and numerical models, has produced a range of hypotheses about landscape sensitivity to climate, but we now need empirical data to test and make sense of these ideas. This thesis therefore explores empirically how geomorphological and sedimentological records have responded to climatic gradients across time and space. In the first part of this thesis, the extent to which spatial climate gradients are recorded by the longitudinal geometry of river channels is investigated. I use a simple stream power erosion law to predict an inverse relationship between channel steepness and average precipitation rate, and then test this theory using data from a variety of study areas and two complementary analytical approaches. Climate is found to be an important control on river longitudinal geometry across a range of climatic and tectonic conditions, in a way that conforms to existing theoretical knowledge and also allows the climatic signal to be discriminated from tectonics. This work therefore demonstrates that a widely-used geomorphological measurement - the channel steepness index - is quantifiably sensitive to climate in tectonically-active areas, and these findings offer a new explanation for geographic variations in channel steepness that cannot be explained by tectonics alone. The second part of this thesis focuses on the sensitivity of simple mountain catchment-alluvial fan systems to climate changes associated with the last glacial-interglacial cycle, as expressed in the south-western United States. First, eight debris flow-dominated systems located in the south-eastern Sierra Nevada, California are examined. I establish a detailed chronostratigraphic model for these fan systems by building upon and integrating existing exposure age constraints reported by others, and additionally developing a new technique for estimating the ages of these fan deposits. This technique is based on calibrating the rate of enlargement of common weathering fractures observed in exposed surface boulders, which are shown to widen at a steady and predictable rate post-deposition, and can be used as reliable age indicators for > 100 ka at this location. Using the detailed temporal record of deposition established for these fan systems, a large ( > 30,000 particle) grain size data set that spans the last full glacial-interglacial cycle is examined. I demonstrate that debris flow grain size is a highly sensitive recorder of past climate changes, capturing the glacial-interglacial cycle as a sustained and high-amplitude time series with a rapid response timescale of < 10 ka. These debris flow deposits become significantly coarser-grained with warming and overall drying of the climate, and this thesis outlines quantitative reasons why this signal can be attributed to increasing storm intensity with warming. Finally, these debris flow-dominated systems are contrasted with two carefully-selected stream flow-dominated fan systems in Death Valley, California. Using measures of down-system grain size fining and a self-similarity model of sediment calibre, sediment flux estimates during arid interglacial and wetter glacial climate conditions are derived and compared. This study shows that a decrease in average rainfall rate of ~ 30 % produced a corresponding decrease in sediment flux of ~ 20 %. However, I also demonstrate the circumstances in which signal buffering due to incision and sediment recycling destroys this climate signal. Consequently, this thesis demonstrates both the causes and results of complexity in the relationship between climate change, geomorphology, and well-dated terrestrial sedimentary records. Ultimately, this is an expression of how sediment transport processes, tectonics, the magnitude-frequency distribution of rainfall, and other factors interact to generate different climate responses in different systems. Nevertheless, for both geomorphic and sedimentological records examined here, I demonstrate that the effects of climate can be quantified clearly: channel steepness can be quantified as a function of rainfall rate; debris flow sedimentology can be quantified as a function of storm intensity; and alluvial fan sedimentology in Death Valley can be quantified as a function of glacial-interglacial climate changes. Essentially, this thesis finds that terrestrial landscapes are sensitive to known climate changes in the recent geological past, and this result is profoundly important for improving our ability to decode geomorphic and stratigraphic archives effectively. The data and ideas within this Ph.D. research provide useful opportunities for (i) testing and updating our models of how sediment routing systems respond to climate, (ii) extracting quantitative information about past climates from the sedimentary record, and (iii) predicting the effects of future climate changes on the landscape.

This thesis provides a basin-level analysis of climate shocks and conflict links, utilising livelihoods and vulnerability toolboxes, including a newly assembled conflict dataset that captures communal, rebel and water conflicts in four Lake Chad Basin (LCB) zones. The thesis draws on multi-method approaches to assess: (i) the manner in which lake drying shapes livelihood drawbacks and opportunities, (ii) the directionality of occupation-based vulnerability to double exposures, (iii) climate conflict interactions in the context of contextual vulnerability and lake drying, and (iv) adaptation-water-conflict integration need for the LCB. Key findings reveal that: (i) asset holdings from unstable water-based activities are a medium through which drying influences livelihoods, (ii) pastoralists are more vulnerable to double exposures because they have limited social networks and income strategies, (iii) rainfall anomalies have dampening effects on conflict and lake drying does not represent a sufficient mediator for climate conflict links. Effects of rainfall anomalies on conflict are more pronounced in the presence of political exclusion in the Chad and Nigeria zones which occupy large areas of the LCB, (iv) policy initiatives increasingly acknowledge the need to preserve the Lake waters, yet initiatives that explicitly integrate adaptation, water and conflict concerns are only beginning to emerge. Two new documents indicating integration have been developed between 2015 and 2016. This thesis is the first to develop a new set of integrated vulnerability tools for use in framing climate conflict vulnerabilities in water scarce environments. It provides a piece of empirically-rich understanding that suggests that climate conflict studies that fail to account for vulnerability forces risk a critical misrepresentation and misunderstanding. The results offer an empirical case to buttress the theoretical critiques already available in the literature. The thesis concludes by outlining recommendations and ways forward that better integrate LCB-related adaptation, water governance and conflict management goals.

The East Asian Monsoon (EAM) is an active component of the global climate system and has a profound social and economic impact in East Asia and its surrounding countries. Its impact on regional hydrological processes may influence society through industrial water supplies, food productivity and energy use. In order to predict future rates of climate change, reliable and accurate reconstructions of regional temperature and rainfall are required from all over the world to test climate models and better predict future climate variability. Hokkaido is a region which has limited palaeo-climate data and is sensitive to climate change. Instrumental data show that the climate in Hokkaido is influenced by the East Asian Monsoon (EAM), however, instrumental data is limited to the past ~150 years. Therefore down-core climate reconstructions, prior to instrumental records, are required to provide a better understanding of the long-term behaviour of the climate drivers (e.g. the EAM, Westerlies, and teleconnections) in this region. The present study develops multi-proxy reconstructions to determine past climatic and hydrologic variability in Japan over the past 1000 years and aid in understanding the effects of the EAM and the Westerlies independently and interactively. A 250-cm long sediment core from Lake Toyoni, Hokkaido was retrieved to investigate terrestrial and aquatic input, lake temperature and hydrological changes over the past 1000-years within Lake Toyoni and its catchment using X-Ray Fluorescence (XRF) data, alkenone palaeothermometry, the molecular and hydrogen isotopic composition of higher plant waxes (δD(HPW)). Here, we conducted the first survey for alkenone biomarkers in eight lakes in the Hokkaido, Japan. We detected the occurrence of alkenones within the sediments of Lake Toyoni. We present the first lacustrine alkenone record from Japan, including genetic analysis of the alkenone producer. C37 alkenone concentrations in surface sediments are 18µg C37 g−1 of dry sediment and the dominant alkenone is C37:4. 18S rDNA analysis revealed the presence of a single alkenone producer in Lake Toyoni and thus a single calibration is used for reconstructing lake temperature based on alkenone unsaturation patterns. Temperature reconstructions over the past 1000 years suggest that lake water temperatures varies between 8 and 19°C which is in line with water temperature changes observed in the modern Lake Toyoni. The alkenone-based temperature reconstruction provides evidence for the variability of the EAM over the past 1000 years. The δD(HPW) suggest that the large fluctuations (∼40‰) represent changes in temperature and source precipitation in this region, which is ultimately controlled by the EAM system and therefore a proxy for the EAM system. In order to complement the biomarker reconstructions, the XRF data strengthen the lake temperature and hydrological reconstructions by providing information on past productivity, which is controlled by the East Asian Summer monsoon (EASM) and wind input into Lake Toyoni, which is controlled by the East Asian Winter Monsoon (EAWM) and the Westerlies. By combining the data generated from XRF, alkenone palaeothermometry and the δD(HPW) reconstructions, we provide valuable information on the EAM and the Westerlies, including; the timing of intensification and weakening, the teleconnections influencing them and the relationship between them. During the Medieval Warm Period (MWP), we find that the EASM dominated and the EAWM was suppressed, whereas, during the Little Ice Age (LIA), the influence of the EAWM dominated with time periods of increased EASM and Westerlies intensification. The El Niño Southern Oscillation (ENSO) significantly influenced the EAM; a strong EASM occurred during El Niño conditions and a strong EAWM occurred during La Niña. The North Atlantic Oscillation, on the other hand, was a key driver of the Westerlies intensification; strengthening of the Westerlies during a positive NAO phase and weakening of the Westerlies during a negative NAO phase. A key finding from this study is that our data support an anti-phase relationship between the EASM and the EAWM (e.g. the intensification of the EASM and weakening of the EAWM and vice versa) and that the EAWM and the Westerlies vary independently from each other, rather than coincide as previously suggested in other studies.

The potential impacts of climate change and environmental variability are already evident in most parts of the world, which is witnessing increasing temperature rates and prolonged flood or drought conditions that affect agriculture activities and nature-dependent livelihoods. This study was conducted in Mwanga District in the Kilimanjaro region of Tanzania to assess the nature and impacts of climate change and environmental variability on agriculture-dependent livelihoods and the adaptation strategies adopted by small-scale rural farmers. To attain its objective, the study employed a mixed methods approach in which both qualitative and quantitative techniques were used. The study shows that farmers are highly aware of their local environment and are conscious of the ways environmental changes affect their livelihoods. Farmers perceived that changes in climatic variables such as rainfall and temperature had occurred in their area over the period of three decades, and associated these changes with climate change and environmental variability. Farmers’ perceptions were confirmed by the evidence from rainfall and temperature data obtained from local and national weather stations, which showed that temperature and rainfall in the study area had become more variable over the past three decades. Farmers’ knowledge and perceptions of climate change vary depending on the location, age and gender of the respondents. The findings show that the farmers have limited understanding of the causes of climatic conditions and environmental variability, as some respondents associated climate change and environmental variability with social, cultural and religious factors. This study suggests that, despite the changing climatic conditions and environmental variability, farmers have developed and implemented a number of agriculture adaptation strategies that enable them to reduce their vulnerability to the changing conditions. The findings show that agriculture adaptation strategies employ both planned and autonomous adaptation strategies. However, the study shows that increasing drought conditions, rainfall variability, declining soil fertility and use of cheap farming technology are among the challenges that limit effective implementation of agriculture adaptation strategies. This study recommends further research on the varieties of drought-resilient crops, the development of small-scale irrigation schemes to reduce dependence on rain-fed agriculture, and the improvement of crop production in a given plot of land. In respect of the development of adaptation strategies, the study recommends the involvement of the local farmers and consideration of their knowledge and experience in the farming activities as well as the conditions of their local environment. Thus, the findings of this study may be helpful at various levels of decision making with regard to the development of climate change and environmental variability policies and strategies towards reducing farmers’ vulnerability to current and expected future changes.