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This paper examines efforts taking place in London, San Francisco and Stockholm to implement deep greenhouse gas emission cuts--'deep decarbonization'--through the transformation of buildings and urban energy infrastructure for increased energy efficiency and low/zero carbon energy supply. Drawing on interviews, policy document analysis, and site tours to buildings and energy infrastructure, this paper analyzes how deep decarbonization is being embedded into urban buildings, energy systems, and institutions. It argues that practitioners are finding ways to create new low/zero carbon future buildings, but are having difficulty correcting the historical development path through retrofitting. This paper examines solutions and challenges brought to light by urban decarbonization in practice targeting existing buildings from which other cities can learn. Four key lessons for low/zero carbon retrofits are highlighted: 1) shift primary targets from homeowners to owners of multiple buildings, 2) expand the suite of resources available to support zero carbon retrofits, 3) experiment and teach using public investment, and 4) institutionalize energy and carbon reporting linked to municipal department targets. Given the necessity of low-carbon, efficient, and climate-resilient building retrofits to address the climate crisis, action can be scaled up by considering buildings and energy infrastructure an infrastructure priority for public investment. Keywords: urban; cities; climate change; decarbonization Cet article examine les efforts deployes a Londres, San Francisco et Stockholm pour mettre en place une reduction profonde des emissions de gaz a effet de serre--<>--par la transformation des batiments et des infrastructures energetiques urbaines pour l'efficacite energetique et l'approvisionnement d'energie a zero ou faible intensite carbone. S'appuyant sur des entretiens, l'analyse de documents de politiques publiques et des visites de sites d'immeubles et d'infrastructures energetiques, cet article analyse comment la decarbonisation en profondeur est incorporee dans les batiments urbains, les systemes energetiques et les institutions. Il fait valoir que les praticiens trouvent des moyens de creer de nouveaux developpements a zero ou faibles emissions de carbone, mais ceux-ci ont du mal a corriger la trajectoire historique de developpement avec l'amelioration energetique. Cet article examine les solutions et les defis mis en evidence par la pratique de la decarbonisation urbaine qui cible les batiments existants, a partir desquels d'autres villes peuvent apprendre. Quatre lecons principales pour la renovation a faibles emissions ou carboneutre sont soulignees: 1) transferer les objectifs principaux des proprietaries aux proprietaries de plusieurs batiments, 2) elargir la gamme de ressources disponibles pour soutenir les ameliorations de la reduction des emissions de carbone, 3) experimenter et enseigner en utilisant les investissements publics et 4) institutionnaliser les rapports sur l'energie et le carbone lies aux objectifs des services municipaux. Compte tenu de la necessite de renover les batiments dans une optique de sobriete carbone, d'efficacite et de resilience face a la crise climatique, il est suggere d'intensifier l'action en considerant les batiments et les infrastructures energetiques comme une priorite pour les investissements publics dans les infrastructures. Mots cles: urbain; villes; changement climatique; decarbonisation, Introduction It is increasingly clear that urban climate change mitigation features diverse and multi-level action driven by actors from across government, industry and non-profit sectors. In this context, a number [...]

The phase shift between changes in the global surface temperature Tg and atmospheric CO2 content has been shown earlier not to characterize causal relationships in the Earth system in the general case. Specifically, the sign of this phase shift under nongreenhouse radiative forcing changes depends on the time scale of this forcing. This paper analyzes the phase shift between changes in the global surface temperature Tg and the atmospheric CO2 content under synchronous external emissions of carbon dioxide and methane into the atmosphere on the basis of numerical experiments with the IAP RAS climatic model and a conceptual climate model with carbon cycle. For a sufficiently large time scale of external forcing, the changes in lag relative to the corresponding changes in Tg. [ABSTRACT FROM AUTHOR]

As the global temperature is on the rise due to global warming, the issue of climate change is indeed a hot topic among the climate scientists and policy-makers worldwide. Claiming anthropogenic emissions as the primary cause of the prevailing climate change, every human activity is now under heavy scrutiny. Among others, mining is one of the fundamental activities which caters to the supply of raw materials to other basic industries and fulfils most of the energy needs of the human race and is believed to be a major contributor to the anthropogenic emissions. The present paper discusses a few case studies conducted in some Indian mines to estimate their respective carbon emissions. The accounting of carbon emissions due to mining activities is called as 'greenhouse gas inventory'. A brief look over the GHG inventory of some mines provides a succinct idea about contribution of mining industry to global emissions. The results highlight that emissions from mining industry are significant and cannot be overlooked. Thus it is required to develop clean technology to be implemented in mines to lower its emissions. [ABSTRACT FROM AUTHOR]

It is now accepted that tourism is a significant contributor to global climate change, especially through air travel's high greenhouse gas emissions. This paper analyses the dilemmas facing tourism planning in many small island developing states and presents a model approach toward overcoming those dilemmas by adapting carbon neutral tourism policies. It researches the implementation issues facing carbon neutral tourism policies on the Seychelles Islands: tourism to the islands is energy-intensive, and current plans to increase tourist numbers will entail growing emissions of greenhouse gases. This paper analyses tourism's current levels of energy use and emissions, and explores ways to reduce them. Based on a survey of tourists and industry representatives in the Seychelles, it discusses options for tourism-dependent small island developing states to implement and finance carbon neutrality, while outlining the complexities and limitations of such an objective. [ABSTRACT FROM AUTHOR]

Global Warming Potential (GWP) is an index used to measure the cumulative radiative forcing of a tonne of greenhouse house gas (GHG) relative to that of a ‘reference’ gas (CO2). Under the Kyoto Protocol, GWP can be used as a fixed index to govern the trade-off between different GHGs in a multi-gas approach to GHGs abatement. The use of fixed GWPs has been criticized for not being very cost effective compared to the use of some flexible indices. To gain wider acceptance, however, a flexible index must also prove to be easy to use, and the economic gains from its adoption must be significant. In this paper, we develop a flexible index based on the concept of marginal rather than cumulative or average global warming potentials. These marginal global warming potentials (MGWPs) can be endogenously determined within a climate model given a particular climate objective based on radiative forcing level. The MGPWs are then linked to the marginal abatement costs of the GHGs, which are also endogenously determined within an economic model. When the two concepts are linked in this way, the result is a cost-effective way of achieving a particular climate change objective with multigas abatement. We show that the savings in costs when using this flexible MGPWs can be significant, and more importantly, they are not uniformly distributed across different regions. [ABSTRACT FROM AUTHOR]

Background, Aims and Scope. The traditional method of using Global Warming Potentials (GWPs) to assess the effects of climate change in Life Cycle Assessment (LCA) does not account for indirect atmospheric effects like saturation effects and emissions of ozone precursors. The aim of this paper is to provide GWP values for LCA purposes of the most important climate related gases including indirect effects and assess whether these values are dependent of different background conditions and size of change in emissions fluxes. Methods. In order to reflect atmospheric interactions between direct and indirect greenhouse gases, an atmospheric climate and chemistry model needs to be used to determine GWP values. Here, the IMAGE model is used to determine GWP values for a time horizon of 100 years. Different runs were performed to test the outcomes against various background emission scenarios and various sizes in emission fluxes. Results and Discussion. The GWP values for CO2, N2O and CH4 depend on the chosen scenario and are lower under scenarios with higher background emissions. The GWPs of Halons, PFCs and SF6 are scenario and emission flux independent. The GWPs of HFCs increase with higher background emissions and higher additional emission fluxes, whereas GWPs of CFC are scenario independent, but change when other emission fluxes are applied. Finally, GWPs of HCFCs are higher in scenarios with higher background emission scenarios, and decrease when larger emission fluxes are applied. The GWP values calculated with IMAGE with direct effects only are comparable with IPCC values. Inclusion of the indirect atmospheric effects changes some of the values positively or negatively. For CFCs this results in a value up to 70% lower. For Halons this results in a value up to 1000% lower, resulting in a strong negative GWP. Inclusion of indirect effects increases the GWP of CH4 by 50%. Newly introduced greenhouse gases which have only indirect effects are given here a GWP. SO2 has a negative GWP which depends on both the flux size and the chosen background scenario. CO and NMVOC have a positive flux-and-scenario dependent GWP. The GWP of NOx can, dependent on de chosen conditions, be positive or negative. Conclusions. The GWP values of this paper are a first attempt to provide a consistent set of GWP values for all direct and indirect greenhouse gases, including differences in GWP values per background scenario and flux size. The inclusion of indirect effects in GWP values causes large differences in some important greenhouse gases, which should not be ignored in LCA- analyses. We suggest for LCA purposes to use GWPs including indirect effects for marginal change and for the most realistic background scenario. However, existing uncertainties in the indirect effects of greenhouse gases demand for a better understanding of the importance of these effects. [ABSTRACT FROM AUTHOR]

A review of the present status of the global warming science is presented in this paper. The term global warming is now popularly used to refer to the recent reported increase in the mean surface temperature of the earth; this increase being attributed to increasing human activity and in particular to the increased concentration of greenhouse gases (carbon dioxide, methane and nitrous oxide) in the atmosphere. Since the mid to late 1980s there has been an intense and often emotional debate on this topic. The various climate change reports (1996, 2001) prepared by the IPCC (Intergovernmental Panel on Climate Change), have provided the scientific framework that ultimately led to the Kyoto protocol on the reduction of greenhouse gas emissions (particularly carbon dioxide) due to the burning of fossil fuels. Numerous peer-reviewed studies reported in recent literature have attempted to verify several of the projections on climate change that have been detailed by the IPCC reports. The global warming debate as presented by the media usually focuses on the increasing mean temperature of the earth, associated extreme weather events and future climate projections of increasing frequency of extreme weather events worldwide. In reality, the climate change issue is considerably more complex than an increase in the earth’s mean temperature and in extreme weather events. Several recent studies have questioned many of the projections of climate change made by the IPCC reports and at present there is an emerging dissenting view of the global warming science which is at odds with the IPCC view of the cause and consequence of global warming. Our review suggests that the dissenting view offered by the skeptics or opponents of global warming appears substantially more credible than the supporting view put forth by the proponents of global warming. Further, the projections of future climate change over the next fifty to one hundred years is based on insufficiently verified climate models and are therefore not considered reliable at this point in time. [ABSTRACT FROM AUTHOR]

There are several air pollution issues that concern the international community at the regional and global level, including acid deposition, heavy metals, persistent organic pollutants, stratospheric ozone depletion, and climate change. Governments at the regional and global levels have entered into various agreements in an effort to deal with these problems. This paper deals with two major global atmospheric change issues: stratospheric ozone depletion and climate change. The focus is on the policy responses of the United States to these global issues. The United States has signed and ratified international agreements to deal with both problems. The Vienna Convention and the Montreal Protocol on Substances that Deplete the Ozone Layer have led to an effort in both developed and developing countries to phase out ozone depleting substances. The United Nations Framework Convention on Climate Change (UNFCCC) has been signed and ratified by over 180 countries. The UNFCC contained no binding targets and timetables for emissions reductions. The Kyoto Protocol (1997) to the UNFCCC did contain targets and timetables for reductions of greenhouse gases on the part of developed countries. The United States has signed but not ratified the Kyoto Protocol. The United States has experienced some movement to reduce greenhouse gas emissions on the part of various levels of government as well as the private sector. The policy process is constantly informed by scientific research. In the case of stratospheric ozone depletion and climate change, much of this work is carried out under the auspices of international scientific panels. From a policy perspective, there is a great deal of interest in the use of indicators for assessing the scope and magnitude of these problems, both for fashioning policy responses as well as assessing the impact of adopted programs to reduce ozone depleting substances, and potentially, greenhouse gases. This paper will discuss some of the indicators used for stratospheric ozone depletion and climate change. [ABSTRACT FROM PUBLISHER]

It is clear that much more drastic and early actions than those that are presently being undertaken are needed to limit the average global temperature increase to 1.5 °C above pre-industrial levels. The Asian region, accounting for a significant portion of global greenhouse gas emissions and growing at a rapid economic pace, has a major role to play in the world's transition to a low carbon society (LCS). To design leapfrog pathways to low carbon and sustainable development, it is important to have a scientific tool that can develop LCS pathways and analyze the effectiveness of policies to achieve them under different scenarios. The Asia-Pacific Integrated Assessment Model (AIM) is an effective tool to support these analyses. It has been developed by researchers in Asia and used in policymaking processes in Asia. It can provide comprehensive and consistent assessment of various policies, including macro-economic policies and technological measures. It can analyze trade-offs between rapid economic growth in Asia and its environmental impact and assess sustainable development policies. This paper presents the processes of designing LCS policies and how modeling tools can support the analyses of the leapfrog pathways to a LCS. As a modeling tool, the family of AIM models is explained and their applications in Asia are presented. Procedures to design and implement low carbon policies together with the Plan-Do-Check-Act cycle are also presented. [ABSTRACT FROM AUTHOR]

A favoured method of assimilating information from state-of-the-art climate models into integrated assessment models of climate impacts is to use the transient climate response (TCR) of the climate models as an input, sometimes accompanied by a pattern matching approach to provide spatial information. More recent approaches to the problem use TCR with another independent piece of climate model output: the land-sea surface warming ratio ( φ). In this paper we show why the use of φ in addition to TCR has such utility. Multiple linear regressions of surface temperature change onto TCR and φ in 22 climate models from the CMIP3 multi-model database show that the inclusion of φ explains a much greater fraction of the inter-model variance than using TCR alone. The improvement is particularly pronounced in North America and Eurasia in the boreal summer season, and in the Amazon all year round. The use of φ as the second metric is beneficial for three reasons: firstly it is uncorrelated with TCR in state-of-the-art climate models and can therefore be considered as an independent metric; secondly, because of its projected time-invariance, the magnitude of φ is better constrained than TCR in the immediate future; thirdly, the use of two variables is much simpler than approaches such as pattern scaling from climate models. Finally we show how using the latest estimates of φ from climate models with a mean value of 1.6-as opposed to previously reported values of 1.4-can significantly increase the mean time-integrated discounted damage projections in a state-of-the-art integrated assessment model by about 15 %. When compared to damages calculated without the inclusion of the land-sea warming ratio, this figure rises to 65 %, equivalent to almost 200 trillion dollars over 200 years. [ABSTRACT FROM AUTHOR]

The UN Framework Convention on Climate Change (UNFCCC) demands stabilization of atmospheric greenhouse gas concentrations at levels that prevent dangerous anthropogenic interference with the climate system. This requires an unprecedented degree of international action for emission reductions and technological change in the energy sector. Extending the established optimal control approach, the paper combines the concepts of adaptive control, inverse modeling and local optimization to climate change decision-making and management. An alternative decision model is described where controls are adjusted towards a moving target under changing conditions. A framework for integrated assessment is introduced, where a basic climate model is coupled to an economic production function with energy as a production factor, which is controlled by the allocation of investments to alternative energy technologies. Investment strategies are shaped by value functions, including utility, costs and climate damages for a given future time horizon, which are translated into admissible emission limits to keep atmospheric carbon concentrations and global mean temperature asymptotically below a given threshold. Conditions for switching between management and technology paths with different costs and carbon intensities are identified. To take account of the substantial uncertainties, an exemplary case discusses the sensitivity of the results to variation of crucial parameters, in particular time discounting, climate damage, taxes and time horizon for decision-making. [ABSTRACT FROM AUTHOR]

Expansion of irrigated land can cause local cooling of daytime temperatures by up to several degrees Celsius. Here the authors compare the expected cooling associated with rates of irrigation expansion in developing countries for historical (1961–2000) and future (2000–30) periods with climate model predictions of temperature changes from other forcings, most notably increased atmospheric greenhouse gas levels, over the same periods. Indirect effects of irrigation on climate, via methane production in paddy rice systems, were not considered. In regions of rapid irrigation growth over the past 40 yr, such as northwestern India and northeastern China, irrigation’s expected cooling effects have been similar in magnitude to climate model predictions of warming from greenhouse gases. A masking effect of irrigation can therefore explain the lack of significant increases in observed growing season maximum temperatures in these regions and the apparent discrepancy between observations and climate model simulations. Projections of irrigation for 2000–30 indicate a slowing of expansion rates, and therefore cooling from irrigation expansion over this time period will very likely be smaller than in recent decades. At the same time, warming from greenhouse gases will likely accelerate, and irrigation will play a relatively smaller role in agricultural climate trends. In many irrigated regions, therefore, temperature projections from climate models, which generally ignore irrigation, may be more accurate in predicting future temperature trends than their performance in reproducing past observed trends in irrigated regions would suggest. [ABSTRACT FROM AUTHOR]

The economic benefits of a multi-gas approach to climate change mitigation are clear. However, there is still a debate on how to make the trade-off between different greenhouse gases (GHGs). The trade-off debate has mainly centered on the use of Global Warming Potentials (GWPs), governing the trade-off under the Kyoto Protocol, with results showing that the cost-effective valuation of short-lived GHGs, like methane (CH4), should be lower than its current GWP value if the ultimate aim is to stabilize the anthropogenic temperature change. However, contrary to this, there have also been proposals that early mitigation mainly should be targeted on short-lived GHGs. In this paper we analyze the cost-effective trade-off between a short-lived GHG, CH4, and a long-lived GHG, carbon dioxide (CO2), when a temperature target is to be met, taking into consideration the current uncertainty of the climate sensitivity as well as the likelihood that this will be reduced in the future. The analysis is carried out using an integrated climate and economic model (MiMiC) and the results from this model are explored and explained using a simplified analytical economic model. The main finding is that the introduction of uncertainty and learning about the climate sensitivity increases the near-term cost-effective valuation of CH4 relative to CO2. The larger the uncertainty span, the higher the valuation of the shortlived gas. For an uncertainty span of ±1°C around an expected climate sensitivity of 3°C, CH4 is cost-effectively valued 6.8 times as high as CO2 in year 2005. This is almost twice as high as the valuation in a deterministic case, but still significantly lower than its GWP100 value. [ABSTRACT FROM AUTHOR]

Global climate change is one of the most important issues of contemporary environmental safety. A scientific consensus is forming that the emissions of greenhouse gases, including carbon dioxide, nitrous oxide and methane, from anthropogenic activities may play a key role in elevating the global temperatures. Quantifying soil greenhouse gas emissions is an essential task for understanding the atmospheric impacts of anthropogenic activities in terrestrial ecosystems. In most soils, production or consumption of the three major greenhouse gases is regulated by interactions among soil redox potential, carbon source and electron acceptors. Two classical formulas, the Nernst equation and the Michaelis–Menten equation, describe the microorganism-mediated redox reactions from aspects of thermodynamics and reaction kinetics, respectively. The two equations are functions of a series of environmental factors (e.g. temperature, moisture, pH, Eh) that are regulated by a few ecological drivers, such as climate, soil properties, vegetation and anthropogenic activity. Given the complexity of greenhouse gas production in soils, process-based models are required to interpret, integrate and predict the intricate relationships among the gas emissions, the environmental factors and the ecological drivers. This paper reviews the scientific basis underlying the modeling of greenhouse gas emissions from terrestrial soils. A case study is reported to demonstrate how a biogeochemical model can be used to predict the impacts of alternative management practices on greenhouse gas emissions from rice paddies. [ABSTRACT FROM AUTHOR]

With the ratification of the Kyoto Protocol, an era of global efforts to combat climate change is beginning. Countries belonging to Annex I Parties are obligated to meet their target in reducing greenhouse gas (GHG) emissions. This paper broadens the scope of research to compare the performance between two groups, Annex II Parties and economies in transition (EIT) Parties (both of which are in the set of Annex I Parties), undertaking responsibilities for GHG emission reduction. This differs from the traditional application of evaluation and aims to identify inherent efficiency differences across systems, rather than separately from the potential inefficiency of individual countries. An efficiency gap was found between the group of Annex II Parties and the group of EIT Parties, by adjusting efficiency levels. Considering a reference set, efficient Annex II countries are referenced, both within their own group and within the EIT group; efficient EIT countries are only benchmarked within the group. The evidence provided can shed light on the function of joint implementation, that Annex I countries will cooperate to reduce GHG emissions, based on their common, but differentiated, responsibilities and capacity for global climate change. [ABSTRACT FROM AUTHOR]

If the objective of the United Nations Framework Convention on Climate Change (UNFCCC) is to be achieved, Parties must commit themselves to meeting meaningful long-term targets that, based on current knowledge, would minimize the possibility of irreversible climate change. Current indications are that a global mean temperature rise in excess of 2–3 °C would enhance the risk of destabilizing the climate system as we know it, and possibly lead to catastrophic change such as a shutdown of the deep ocean circulation, and the disintegration of the West Arctic Ice Sheet. Observations have shown that for many small island developing States (SIDS), life-sustaining ecosystems such as coral reefs, already living near the limit of thermal tolerance, are highly climate-sensitive, and can suffer severe damage from exposure to sea temperatures as low as 1 °C above the seasonal maximum. Other natural systems (e.g., mangroves) are similarly susceptible to relatively low temperature increases, coupled with small increments of sea level rise. Economic and social sectors, including agriculture and human health, face similar challenges from the likely impacts of projected climate change. In light of known thresholds, this paper presents the view that SIDS should seek support for a temperature cap not exceeding 1.5–2.0 °C above the pre-industrial mean. It is argued that a less stringent post-Kyoto target would frustrate achievement of the UNFCCC objective. The view is expressed that all countries which emit significant amounts of greenhouse gases should commit to binding reduction targets in the second commitment period, but that targets for developing countries should be less stringent than those agreed for developed countries. Such an arrangement would be faithful to the principles of equity and would ensure that the right of Parties to attain developed country status would not be abrogated. [ABSTRACT FROM AUTHOR]

The detection and attribution of climate change in the observed record play a central role in synthesizing knowledge of the climate system. Unfortunately, the traditional method for detecting and attributing changes due to multiple forcings requires large numbers of general circulation model (GCM) simulations incorporating different initial conditions and forcing scenarios, and these have only been performed with a small number of GCMs. This paper presents an extension to the fingerprinting technique that permits the inclusion of GCMs in the multisignal analysis of surface temperature even when the required families of ensembles have not been generated. This is achieved by fitting a series of energy balance models (EBMs) to the GCM output in order to estimate the temporal response patterns to the various forcings. This methodology is applied to the very large Challenge ensemble of 62 simulations of historical climate conducted with the NCAR Community Climate System Model version 1.4 (CCSM1.4) GCM, as well as some simulations from other GCMs. Considerable uncertainty exists in the estimates of the parameters in fitted EBMs. Nevertheless, temporal response patterns from these EBMs are more reliable and the combined EBM time series closely mimics the GCM in the context of transient forcing. In particular, detection and attribution results from this technique appear self-consistent and consistent with results from other methods provided that all major forcings are included in the analysis. Using this technique on the Challenge ensemble, the estimated responses to changes in greenhouse gases, tropospheric sulfate aerosols, and stratospheric volcanic aerosols are all detected in the observed record, and the responses to the greenhouse gases and tropospheric sulfate aerosols are both consistent with the observed record without a scaling of the amplitude being required. The result is that the temperature difference of the 1996–2005 decade relative to the 1940–49 decade can be attributed to greenhouse gas emissions, with a partially offsetting cooling from sulfate emissions and little contribution from natural sources. The results support the viability of the new methodology as an extension to current analysis tools for the detection and attribution of climate change, which will allow the inclusion of many more GCMs. Shortcomings remain, however, and so it should not be considered a replacement to traditional techniques. [ABSTRACT FROM AUTHOR]

This paper describes the mean ocean circulation and the tropical variability simulated by the Max Planck Institute for Meteorology (MPI-M) coupled atmosphere–ocean general circulation model (AOGCM). Results are presented from a version of the coupled model that served as a prototype for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) simulations. The model does not require flux adjustment to maintain a stable climate. A control simulation with present-day greenhouse gases is analyzed, and the simulation of key oceanic features, such as sea surface temperatures (SSTs), large-scale circulation, meridional heat and freshwater transports, and sea ice are compared with observations. A parameterization that accounts for the effect of ocean currents on surface wind stress is implemented in the model. The largest impact of this parameterization is in the tropical Pacific, where the mean state is significantly improved: the strength of the trade winds and the associated equatorial upwelling weaken, and there is a reduction of the model’s equatorial cold SST bias by more than 1 K. Equatorial SST variability also becomes more realistic. The strength of the variability is reduced by about 30% in the eastern equatorial Pacific and the extension of SST variability into the warm pool is significantly reduced. The dominant El Niño–Southern Oscillation (ENSO) period shifts from 3 to 4 yr. Without the parameterization an unrealistically strong westward propagation of SST anomalies is simulated. The reasons for the changes in variability are linked to changes in both the mean state and to a reduction in atmospheric sensitivity to SST changes and oceanic sensitivity to wind anomalies. [ABSTRACT FROM AUTHOR]

The consistency between observed changes in Subantarctic Mode Water (SAMW) properties at 32°S in the Indian Ocean and model simulations is explored using the Third Hadley Centre Coupled Ocean–Atmosphere GCM (HadCM3). Hydrographic data collected in 2002 show that the water mass is warmer and saltier on isopycnals than in 1987, in contrast to the isopycnal freshening observed between 1962 and 1987. The response of HadCM3 under a range of forcing scenarios is explored and the observed freshening is only seen in experiments that include greenhouse gas forcing; however, there is no subsequent return to more saline conditions in 2002. The response of the model to greenhouse gas forcing is dominated by a persistent freshening trend, the simulated water mass variability agrees well with that suggested by the limited observations. Comparing model isopycnal changes from the forced experiments with a control run shows that the changes from the 1960s to 2002 are best explained by internal variability. This is in contrast to earlier work, which attributed the observed isopycnal freshening to anthropogenic forcing. Although the model shows that at present an anthropogenic climate change signal is not detectable in SAMW, the model water mass freshens on isopycnals during the twenty-first century under increased greenhouse gas forcing. This is consistent with recent heat content observations, which suggest that the salting is unlikely to persist. In HadCM3, this freshening is due to an increasing surface heat flux and Ekman heat and freshwater flux into the water mass formation region. This paper emphasizes the importance of higher-frequency observations of SAMW if detection and attribution statements are to be made. [ABSTRACT FROM AUTHOR]

This paper examines different concepts of a 'warming commitment' which is often used in various ways to describe or imply that a certain level of warming is irrevocably committed to over time frames such as the next 50 to 100 years, or longer. We review and quantify four different concepts, namely (1) a 'constant emission warming commitment', (2) a 'present forcing warming commitment', (3) a 'zero emission (geophysical) warming commitment' and (4) a 'feasible scenario warming commitment'. While a 'feasible scenario warming commitment' is probably the most relevant one for policy making, it depends centrally on key assumptions as to the technical, economic and political feasibility of future greenhouse gas emission reductions. This issue is of direct policy relevance when one considers that the 2002 global mean temperatures were 0.8 ± 0.2°C above the pre-industrial (1861-1890) mean and the European Union has a stated goal of limiting warming to 2°C above the pre-industrial mean: What is the risk that we are committed to overshoot 2°C? Using a simple climate model (MAGICC) for probabilistic computations based on the conventional IPCC uncertainty range for climate sensitivity (1.5 to 4.5 °C), we found that (1) a constant emission scenario is virtually certain to overshoot 2°C with a central estimate of 2.0°C by 2100 (4.2°C by 2400). (2) For the present radiative forcing levels it seems unlikely that 2°C are overshoot. (central warming estimate 1.1 °C by 2100 and 1.2°C by 2400 with ∼10% probability of overshooting 2°C). However, the risk of overshooting is increasing rapidly if radiative forcing is stabilized much above 400 ppm CO2 equivalence (1.95 W/m²) in the long-term. (3) From a geophysical point of view, if all human-induced emissions were ceased tomorrow, it seems 'exceptionally unlikely' that 2°C will be overshoot (central estimate: 0.7°C by 2100; 0.4°C by 2400). (4) Assuming future emissions according to the lower end of published mitigation scenarios (350 ppm CO2eq to 450 ppm CO2eq) provides the central temperature projections are 1.5 to 2.1 °C by 2100 (1.5 to 2.0°C by 2400) with a risk of overshooting 2°C between 10 and 50% by 2100 and 1-32% in equilibrium. Furthermore, we quantify the 'avoidable warming' to be 0.16-0.26°C for every 100 GtC of avoided CO2 emissions - based on a range of published mitigation scenarios. [ABSTRACT FROM AUTHOR]

Any discussion of the benefits of greenhouse gas (GHG) mitigation measures should take into consideration the full range of possible climate change outcomes, including impacts that remain highly uncertain, like surprises and other climate irreversibilities. Real-world coupling between complex systems can cause them to exhibit new collective behaviours that are not clearly demonstrable by models that do not include such coupling. Through examples from ocean circulation and atmosphere–biosphere interactions, this paper demonstrates that external forcings such as increases in GHG concentrations can push complex systems from one equilibrium state to another, with non-linear abrupt change as a possible consequence. Furthermore, the harder and faster a system is perturbed, the higher the likelihood of such surprises—a conclusion that has significant bearing on the assessment of the potential benefits of the timing and stringency of GHG abatement measures. The paper concludes with a perspective on how to better incorporate uncertainty and surprise into integrated assessment models of climate change. [Copyright &y& Elsevier]

Climate change due to greenhouse gas emissions is predicted to raise the mean global temperature by 1.0–3.5°C in the next 50–100 years. The direct and indirect effects of this potential increase in temperature on terrestrial ecosystems and ecosystem processes are likely to be complex and highly varied in time and space. The Global Change and Terrestrial Ecosystems core project of the International Geosphere-Biosphere Programme has recently launched a Network of Ecosystem Warming Studies, the goals of which are to integrate and foster research on ecosystem-level effects of rising temperature. In this paper, we use meta-analysis to synthesize data on the response of soil respiration, net N mineralization, and aboveground plant productivity to experimental ecosystem warming at 32 research sites representing four broadly defined biomes, including high (latitude or altitude) tundra, low tundra, grassland, and forest. Warming methods included electrical heat-resistance ground cables, greenhouses, vented and unvented field chambers, overhead infrared lamps, and passive night-time warming. Although results from individual sites showed considerable variation in response to warming, results from the meta-analysis showed that, across all sites and years, 2–9 years of experimental warming in the range 0.3–6.0°C significantly increased soil respiration rates by 20% (with a 95% confidence interval of 18–22%), net N mineralization rates by 46% (with a 95% confidence interval of 30–64%), and plant productivity by 19% (with a 95% confidence interval of 15–23%). The response of soil respiration to warming was generally larger in forested ecosystems compared to low tundra and grassland ecosystems, and the response of plant productivity was generally larger in low tundra ecosystems than in forest and grassland ecosystems. With the exception of aboveground plant productivity, which showed a greater positive response to warming in colder ecosystems, the magnitude of the response of these three processes to experimental warming was not generally significantly related to the geographic, climatic, or environmental variables evaluated in this analysis. This underscores the need to understand the relative importance of specific factors (such as temperature, moisture, site quality, vegetation type, successional status, land-use history, etc.) at different spatial and temporal scales, and suggests that we should be cautious in "scaling up" responses from the plot and site level to the landscape and biome level. Overall, ecosystem-warming experiments are shown to provide valuable insights on the response of terrestrial ecosystems to elevated temperature. [ABSTRACT FROM AUTHOR]

This article discusses climate change and hurricanes. Papers that appeared in the scholarly journals "Nature" and "Science" during the summer of 2005 raised the question of global warming being the cause of the record-breaking hurricane season of 2005. The article examines that argument, noting that many scientists believe that human-induced climate warming is indeed real. Also discussed is the increasing intensity of hurricanes since 1975, as well as the rise in seas surface temperatures and greenhouse gases in the atmosphere.

There are heated debates on the existence of the global warming slowdown during the early twenty-first century. Although efforts have been made to clarify or reconcile the controversy over this issue, it is not explicitly addressed, restricting the understanding of global temperature change particularly under the background of increasing greenhouse gas concentrations. Here, using extensive temperature datasets, we comprehensively reexamine the existence of the slowdown under all existing definitions during all decadal-scale periods spanning 1990–2017. Results show that the short-term linear trend–dependent definitions of slowdown make its identification severely suffer from the period selection bias, which largely explains the controversy over its existence. Also, the controversy is further aggravated by the significant impacts of the differences between various datasets on the recent temperature trend and the different baselines for measuring slowdown prescribed by various definitions. However, when the focus is shifted from specific periods to the probability of slowdown events, we find the probability is significantly higher in the 2000s than in the 1990s, regardless of which definition and dataset are adopted. This supports a slowdown during the early twenty-first century relative to the warming surge in the late twentieth century, despite higher greenhouse gas concentrations. Furthermore, we demonstrate that this decadal-scale slowdown is not incompatible with the centennial-scale anthropogenic warming trend, which has been accelerating since 1850 and never pauses or slows. This work partly reconciles the controversy over the existence of the warming slowdown and the discrepancy between the slowdown and anthropogenic warming. [ABSTRACT FROM AUTHOR]

Climate change is now an indisputable challenge to the sustainability of human development. The effects of global warming, especially anthropogenic, affect all economic and productive sectors, stimulating a broad debate about the best and more suited tools and strategies to put in place to resist but also to overcome this challenge. European agriculture that is currently discussing on the trajectories post-2013, has a strong interest in the issue of climate change, not only because agricultural activities are directly dependent on climatic conditions, but because also agriculture contributes to the release of greenhouses gases in the atmosphere. Based on these considerations, the aim of this paper is to analyze the Common Agricultural Policy (CAP) in the light of a new interpretive scheme of its future directions, in order to verify the actual effectiveness in the implementation of development strategies of the sector, able to ensure sustainability in its various dimensions: economic, social, environmental, territorial and generational. [ABSTRACT FROM AUTHOR]

In the past several decades, the tropospheric westerly winds in the Southern Hemisphere have been observed to accelerate on the poleward side of the surface wind maximum. This has been attributed to the combined anthropogenic effects of increasing greenhouse gases and decreasing stratospheric ozone and is predicted to continue by the Intergovernmental Panel on Climate Change/Fourth Assessment Report (IPCC/AR4) models. In this paper, the predictions of the Chemistry-Climate Model Validation (CCMVaI) models are examined: Unlike the AR4 models, the CCMVaI models have a fully interactive stratospheric chemistry. Owing to the expected disappearance of the ozone hole in the first half of the 21st century, the CCMVaI models predict that the tropospheric westerlies in Southern Hemisphere summer will be decelerated, on the poleward side, in contrast with the prediction of most IPCC/AR4 models. [ABSTRACT FROM AUTHOR]

The economy-wide implications of sea level rise in 2050 are estimated using a static computable general equilibrium model. This allows for a better estimate of the welfare effects of sea level rise than the common direct cost estimates; and for an estimate of the impact of sea level rise on greenhouse gas emissions. Overall, general equilibrium effects increase the welfare costs of sea level rise, but not necessarily in every sector or region. In the absence of coastal protection, economies that rely most on agriculture are hit hardest. Although energy is substituted for land, overall energy consumption falls with the shrinking economy, hurting energy exporters. With full coastal protection, GDP increases, particularly in regions with substantial dike building, but utility falls, least in regions that protect their coasts and export energy. Energy prices rise and energy consumption falls. The costs of full protection exceed the costs of losing land. The results also show direct costs – the usual method for estimating welfare changes due to sea level rise – are a bad approximation of the general equilibrium welfare effects; previous estimates of the economic impact of sea level rise are therefore biased. [ABSTRACT FROM AUTHOR]

The aim of this paper is to evaluate current knowledge and uncertainties associated with the impact of increasing greenhouse gas and aerosol concentrations on the West African monsoon. For this purpose, coupled and time-slice simulations are used. A global measure of the monsoon changes is defined in order to avoid regional biases and to try and obtain significant results. The position and width of the monsoon in latitude are the main focuses. There is almost no agreement between the Coupled General Circulation models from the Coupled models Inter-Comparison project—Phase II in regard to the impact of climate change on the monsoon. Moreover, very simple discriminations between the models seem inappropriate to get a better signal. The role of the different forcings in time-slice simulations is then investigated. The sea surface temperature (SST) and particularly the pattern of the SST are shown to be the most important forcing. This accounts for the diversity of the results either from the coupled or the forced simulations with different SST changes. With a fixed SST, but of a smaller magnitude in AMJ, there are still uncertainties, coming first from the Atmospheric General Circulation models and the way they balance greenhouse gas and global SST increase. Finally the uncertainty due to the Land Surface models (LSMs) is not negligible. The greenhouse gas and the LSMs are shown to have more impact in August, when the monsoon is at its highest latitude on the continent. [ABSTRACT FROM AUTHOR]

It has been identified that, long-term climatic changes (Pleistocene ice ages) have been caused by periodic changes in the distribution of incoming solar radiation due to the variations in the earth’s orbital geometry, that is the tilt, precision of equinoxes and eccentricity which take place with periodicity ranging from 41 to 9508 thousand years. However, it has been considered that the major potential mechanism of climate change over the next few hundred years will be anthropogenic green house gas warming up. A number of gases that occur naturally in the atmosphere in small quantities are known as ”greenhouse gases. Water vapour, carbon dioxide, ozone, methane, and nitrous oxide trap solar energy in much the same way as do the glass panes of a greenhouse or a closed automobile. This natural greenhouse gases effect has kept the earth’s atmosphere some 30°C hotter, than it would otherwise be, making it possible for humans to exist on earth. Human activities, however, are now raising the concentrations of these gases in the atmosphere and thus increasing their ability to trap energy. The enhanced greenhouse gas effect is expected to cause high temperature increase globally (1–3.5°C) and this will lead to an increase in precipitation in some regions while other regions will experience reduced precipitation (±20%). The impact of expected climate change will affect almost all the sectors of the human endeavor. However, the major purpose of this project is to evaluate the impact of climate change on hydrology and water resources and establish the appropriate adaptation strategies for Swaziland. The impact of climate change on hydrology and water resources will be evaluated using General Circulation Model results (rainfall, potential evapotranspiration, air temperature, etc.) as inputs to a rainfall runoff model. Water use in all the sectors of the human endeavor will be determined in order to establish the water availability given different climate change scenarios. Three catchments have been selected for this exercise. This paper therefore, presents the background information, objectives and significance of the study, literature review, methodology, data collection and processing. [Copyright &y& Elsevier]

• Comprehensive exploration and critique of aerogels as promising CO 2 -capture materials. • Perspectives on aerogels' tunable surface chemistry and proper textural properties. • Focus on characterisation, process economics and performance. • Detailed outlook towards prospects for future CO 2 -capture deployment. Recently, greenhouse gases - especially CO 2 – have been released into the atmosphere in ever-increasing quantities through activities such as industrial emission and combustion. Owing to their high absorption capacities, they appear to be implicated causatively in observed increases in surface temperature and global climate changes. Between porous solid sorbents, aerogels have recently been considered as promising adsorbents for CO 2 capture due to their tunable surface chemistry and proper textural properties. Currently, a variety of different aerogels are being developed at laboratory scale, and some of them have been taken to pilot production. In order to explore the commercialisation-feasibility of aerogels as CO 2 capture adsorbents, more research needs to be done on low-cost materials and production processes, with low or controlled sorption of water as well as a good thermal regeneration capacity. In this review paper, different aspects of scientific investigations on CO 2 -sorption applications of aerogels have been studied. The review contains seven main sections: preparation, characterisation, modification of aerogels, literature studies on CO 2 -sorption performances, kinetic and thermodynamic models on CO 2 adsorption, important factors on CO 2 capture and outlook for future perspectives. [ABSTRACT FROM AUTHOR]

An option-value (or stopping-rule) model is developed to determine the optimal timing and expected value of policies (bullets) to slow global warming. The model and policies are calibrated to reflect current estimates or predictions of temperature drift, variance, damage, and the cost of slowing global warming. The ‘basic’ and ‘asymptotic’ bullets have option values of between $600 and $700 billion dollars for a discount rate of 5 percent. The most effective (platinum) bullet is not adopted until mean global temperature reaches a trigger value of 15.54°C, which is not likely to be reached during the next two decades. [ABSTRACT FROM AUTHOR]

The article comments on paper published in the issue on global warming. The author discusses that findings showed that greenhouse gases in the earth's atmosphere are already enough to cause global calamity. He questions the plans by the United Nations Framework Convention on Climate Change and comments on the findings of the paper.

This article tracks the intergovernmental negotiations aimed at combatting human-induced greenhouse gas emissions under the United Nations Framework Convention on Climate Change from COP21 and the creation of the Paris Agreement in 2015 to COP24 in Katowice, Poland in 2018. These conferences are explored in detail, focusing on the Pans Rulebook negotiations around how to implement market- and nonmarket-based approaches to mitigating climate change, as set out in Article 6 of the Paris Agreement, and the tensions regarding the inclusion of negotiating text safeguarding human rights. A concluding section comments on the collapse of Article 6 discussions and the implications for climate justice and social quality for the Paris Agreement going forward. Keywords: human rights, market mechanisms, Paris Agreement, Paris Rulebook, social quality, The Inconvenient Truth of Too Much Carbon in the Atmosphere While the Paris Agreement provides a means for all countries, rich and poor, to collectively reduce emissions, keeping global temperatures [...]

The article offers information on Global politics of climate change policy. It mentions the rising of Greenhouse gas emissions and human activity which associated with industrialization that made rise in average global temperatures; also focuses on work of governments to balance competing policy priorities of economic growth, job security, industrial competitiveness, and environmental protection along with an resorting to extreme rhetoric against ineffectual action which makes domestic and international agreement through compromise.

The ecosystem and societal development in arid Central Asia are highly vulnerable to climate change. During the past five decades, significant warming occurs in Central Asia, but whether the influence of anthropogenic forcing is detectable remains unclear. Therefore, we employ the optimal fingerprinting method to address the question in this study. The observed annual mean temperature (°C) over Central Asia significantly increases by 1.33 from 1961 to 2005, which mainly concentrates in summer (0.90), autumn (1.22), and winter (2.48). The influence of anthropogenic forcing, particularly the greenhouse gases (GHG) forcing, on both the annual and seasonal significant warming trends are robustly detected. GHG increases the annual, summer, autumn, and winter mean temperature (°C) by 1.25 (0.52–2.00), 1.11 (0.32–1.92), 1.11 (0.40–1.83), and 2.50 (0.91–4.34), respectively. Attribution results demonstrate an underestimation (overestimation) of CMIP5 models in simulating the annual and winter (summer and autumn) historical warming trend in Central Asia, implying a potential bias of the future temperature projections reported in IPCC AR5. Thus, we adjust the projections based on the attributed scaling factors, showing that the projected annual, summer, autumn, and winter mean temperature would significantly increase at a rate (°C decade−1) of 0.32 (0.16–0.49), 0.20 (0.06–0.35), 0.24 (0.10–0.38) and 0.58 (0.24–0.93) under RCP4.5, while 0.74 (0.36–1.12), 0.48 (0.14–0.84), 0.58 (0.25–0.91), and 1.25 (0.53–2.02) under RCP8.5, respectively, demonstrating large annual variation. To the end of twenty-first century, the annual (winter) mean temperature (°C) over Central Asia would increase by 7.00 (11.75) under RCP8.5, 0.85 (5.17) higher than the unadjusted results. [ABSTRACT FROM AUTHOR]

Palaeoclimate reconstructions of periods with warm climates and high atmospheric CO.sub.2 concentrations are crucial for developing better projections of future climate change. Deep-ocean.sup.1,2 and high-latitude.sup.3 palaeotemperature proxies demonstrate that the Eocene epoch (56 to 34 million years ago) encompasses the warmest interval of the past 66 million years, followed by cooling towards the eventual establishment of ice caps on Antarctica. Eocene polar warmth is well established, so the main obstacle in quantifying the evolution of key climate parameters, such as global average temperature change and its polar amplification, is the lack of continuous high-quality tropical temperature reconstructions. Here we present a continuous Eocene equatorial sea surface temperature record, based on biomarker palaeothermometry applied on Atlantic Ocean sediments. We combine this record with the sparse existing data.sup.4-6 to construct a 26-million-year multi-proxy, multi-site stack of Eocene tropical climate evolution. We find that tropical and deep-ocean temperatures changed in parallel, under the influence of both long-term climate trends and short-lived events. This is consistent with the hypothesis that greenhouse gas forcing.sup.7,8, rather than changes in ocean circulation.sup.9,10, was the main driver of Eocene climate. Moreover, we observe a strong linear relationship between tropical and deep-ocean temperatures, which implies a constant polar amplification factor throughout the generally ice-free Eocene. Quantitative comparison with fully coupled climate model simulations indicates that global average temperatures were about 29, 26, 23 and 19 degrees Celsius in the early, early middle, late middle and late Eocene, respectively, compared to the preindustrial temperature of 14.4 degrees Celsius. Finally, combining proxy- and model-based temperature estimates with available CO.sub.2 reconstructions.sup.8 yields estimates of an Eocene Earth system sensitivity of 0.9 to 2.3 kelvin per watt per square metre at 68 per cent probability, consistent with the high end of previous estimates.sup.11.A 26-million-year record of equatorial sea surface temperatures reveals synchronous changes of tropical and polar temperatures during the Eocene epoch forced by variations in concentrations of atmospheric carbon dioxide, with a constant degree of polar amplification., Author(s): Margot J. Cramwinckel [sup.1] , Matthew Huber [sup.2] , Ilja J. Kocken [sup.1] , Claudia Agnini [sup.3] , Peter K. Bijl [sup.1] , Steven M. Bohaty [sup.4] , Joost [...]

The Arctic is experiencing rapid climate change in response to changes in greenhouse gases, aerosols, and other climate drivers. Emission changes in general, as well as geographical shifts in emissions and transport pathways of short‐lived climate forcers, make it necessary to understand the influence of each climate driver on the Arctic. In the Precipitation Driver Response Model Intercomparison Project, 10 global climate models perturbed five different climate drivers separately (CO2, CH4, the solar constant, black carbon, and SO4). We show that the annual mean Arctic amplification (defined as the ratio between Arctic and the global mean temperature change) at the surface is similar between climate drivers, ranging from 1.9 (± an intermodel standard deviation of 0.4) for the solar to 2.3 (±0.6) for the SO4 perturbations, with minimum amplification in the summer for all drivers. The vertical and seasonal temperature response patterns indicate that the Arctic is warmed through similar mechanisms for all climate drivers except black carbon. For all drivers, the precipitation change per degree global temperature change is positive in the Arctic, with a seasonality following that of the Arctic amplification. We find indications that SO4 perturbations produce a slightly stronger precipitation response than the other drivers, particularly compared to CO2. Key Points: Arctic amplification of surface warming is similar between global drivers of climate changeBlack carbon induces differing vertical and seasonal amplification patternsSulfate affects Arctic precipitation responses more strongly than other drivers, particularly in the summer season [ABSTRACT FROM AUTHOR]

Discusses a report from the U.S. National Academies' National Research Council warning of sudden, catastrophic effects from global warming. Details of the report, 'Abrupt Climate Change: Inevitable Surprises,' written by the Committee on Abrupt Climate Change; Suggestion for policies to reduce emissions of greenhouse gases and improve water, land and air quality; Thoughts of global warming expert Dr. Paul Epstein.

We apply a novel method based upon 'before' and 'after' relationships to investigate and quantify interconnections between global temperature anomaly (GTA), as response variable, and greenhouse gases (CO) and total solar irradiance (TSI) as candidate causal variables for the period 1880 to 2010. The most likely interpretations of our results for the 6 to 8 years cyclic components of the variables are that during the period 1929 to 1936, CO significantly leads GTA. However, during the period 1960-2003, GTA apparently leads CO, that is, the peaks (and troughs) in GTA are in front of, and close to, the peaks (and troughs) in CO For time windows outside these periods, we did not find significant before or after-relations. An alternative interpretation is that there is a shift between short (≈1.5 year) and long (≈5 years) durations between cause and effect. Relationships between GTA and TSI suggest that 'inertia' of the global sea, land, and atmosphere system leads to delays longer than half their common cycle length of about 10 years. Based on the interaction patterns between the variables GTA, CO, and TSI, we suggest the possibility that a new regime for how the variables interact started around 1960. From trend forms, and not considering physical mechanisms, we found that the trend in CO contributes ≈ 90 %, and the trend in TSI ≈ 10 %, to the trend in GTA during the last 130 years. [ABSTRACT FROM AUTHOR]