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This work deals with reconstructing firn layer thicknesses at the deposition time from the firn's observed thickness in ice cores, thus reconstructing the annual accumulation, yielding a timescale and an ice-core chronology. We employed a dynamic time warping algorithm to find an optimal, non-linear alignment between an H2O2 concentration data series from 98 m worth of ice cores of a borehole on the central ice divide of the Detroit Plateau, the Antarctic Peninsula, and an estimated local temperature time series. The viability and the physical reliability of the procedure are rooted in the robustness of the seasonal marker H2O2 in a high-accumulation context, which brought the entire borehole to within the operational life span of four Antarctic stations around the Antarctic Peninsula. The process was heavily based on numerical optimisation, producing a mathematically sound match between the two series to estimate the annual layering efficiently on the entire data section at once, being disposition-free. The results herein confirm a high annual accumulation rate of aN=2.8 m w.e./yr, which is of the same order of magnitude as and highly correlated with that of the Bruce Plateau and twice as large as that of the Gomez Plateau, 300 and 1200 km further south, respectively.

Individual glacier changes are still poorly documented in the Georgian Caucasus. In this paper, the change of Chalaati and Zopkhito glaciers in Georgian Caucasus has been studied between 1960 and 2014. Glacier geometries are reconstructed from archival topographic maps, Corona and Landsat images, along with modern field surveys. For the first time in the Georgian Caucasus aerial photogrammetric survey of both glacier termini was performed (2014) using a drone or Unmanned Aerial Vehicle, where high-resolution orthomosaics and digital elevation models were produced. We show that both glaciers have experienced area loss since 1960: 16.2±4.9 per cent for Chalaati Glacier and 14.6±5.1 per cent for Zopkhito Glacier with corresponding respective terminus retreat by ~675 m and ~720 m. These were accompanied by a rise in the equilibrium line altitudes of ~35 m and ~30 m, respectively. The glacier changes are a response to regional warming in surface air temperature over the last half century. We used a long-term temperature record from the town of Mestia and short-term meteorological observations at Chalaati and Zopkhito glaciers to estimate a longer-term air temperature record for both glaciers. This analysis suggests an increase in the duration of the melt season over the 54-year period, indicating the importance of summertime air temperature trends in controlling glacier loss in the Georgian Caucasus. We also observed supra-glacial debris cover increase for both glaciers over the last half century: from 6.16±6.9 per cent to 8.01±6.8 per cent for Chalaati Glacier and from 2.80±6.3 per cent to 8.53±5.7 per cent for Zopkhito Glacier.

Previous studies on surface temperature reconstructions for the last 2000 years (2 k) revealed a long-term cooling trend for the last millennium in comparison to the previous millennium. However, knowledge on the decadal- to centennial-scale variability in sea surface temperature and the underlying governing mechanisms throughout the period is limited. We reconstructed high-resolution continuous sea surface temperature changes over the last 2 k in the northwest Pacific margin based on the alkenone unsaturation index. Our alkenone temperature record revealed enhanced and more rapidly changing climate variability during the last millennium (approximately 1200–1850 Common Era) than during the previous millennium. Cold and hot extremes also occurred more frequently during the last millennium. The enhanced and rapidly changing climate variability appears to be associated with frequent volcanic eruptions and grand solar minima. The reconstructed surface temperature variability tends to be associated with variations in the East Asia summer monsoon and the Pacific Decadal Oscillation, implying that these variations are also enhanced in the last millennium than in the previous millennium.

Multiple potential tipping points in the Earth system that involve alternative states have been identified that are susceptible to anthropogenic forcing. Past events—from millions of years ago to within the last century—have manifest as abrupt changes in climatic indicators such as the temperature record. Recent unprecedented heat waves in Australia, their associated devastation, and the considerations above provide motivation to ask whether the Australian daily maximum temperature record has been subject to such abrupt changes. Using a new diagnostic tool—the Lyapunov plot—here it is shown that multiple temperature transitions have occurred with respect to the maximum daily temperature record in widely separated locations in Australia over the last 150 years. All maximum Lyapunov exponents are positive in sign, indicating that the transitions are chaos-to-chaos transitions, and that the different climate modes identified are likely to be manifestations of distinct chaotic attractors. Many of these events occur simultaneously with transitions or extremes in the major natural cycles affecting Australia’s climate, but this observation is not universal. It is known that chaos-to-chaos transitions can result in changes in the value(s) of the state variable(s) that can range from subtle to severe. Although the identified transitions are not catastrophic, this observation does not rule out the possibility of severe, unprecedented, and discontinuous increases in average daily maximum temperatures occurring in Australia at any time within the next few decades.

To help understanding the potential relationship between chemical weathering and Indian summer monsoon (ISM) since the last glacial period a gravity core (BoB-56) was retrieved from the central Bay of Bengal (BoB). The data of chemical weathering indexes (CIA, WIP, and αAlNa) used in this study showed general synchronicity with the regional monsoon precipitation and temperature record on precessional scale, indicating existence of control from the ISM on weathering. Corresponding to alteration of warm/cold period during the last deglaciation, obvious simultaneously alteration of higher/lower values of the chemical weathering and terrestrial input proxies’ record support our hypothesis that the ISM driving chemical weathering on the millennial scale. However, a contradiction occurred during the Holocene period, when the ISM precipitation and temperature rose to a higher level, while the alternative indexes unanimously reflected a weaker chemical weathering conditions. In this study, we discussed the applicability of chemical weathering indexes in the BoB during the Holocene period. Besides the possible weakened monsoon during 6–3 ka, recorded by the stalagmite δ18O and Sea Surface Temperature (SST) reconstruction results in the northeastern Indian Ocean, other factors were responsible for this phenomenon, including the grain size effect and distinction between the mountain high land and floodplain low land. The chemical weathering records, during the last glaciation, indicated the presence of control from the ISM on weathering at precessional and millennial scales. While, during the Holocene, they failed to reflect the actual chemical weathering dynamics of the source area. Indeed, a mixture of physical erosion and chemical weathering seems to be representative of the chemical weathering dynamics in the area. Our findings emphasized on the tight connections between the chemical weathering evolution and global-regional climate conditions around the BoB, implying possible ISM-controlled mechanisms during different time scales.

The Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) concluded that warming of the climate system since the start of the instrumental record was unequivocal. While this conclusion does not solely rest upon the surface temperature record, this record is a key aspect underpinning this finding. In this chapter, the basis for the observational evidence for increases in global surface temperatures, since the start of the instrumental record, is discussed. The chapter begins with a discussion on how the measurements have been taken over time. This is followed by a description of the necessary efforts required to adjust the records to account for time varying biases. The resulting global estimates and attempts at quantifying uncertainties are then discussed. The changes in temperature extremes are briefly highlighted and the chapter closes with a view to future research directions and innovations.

The thermometer, a device for measuring temperature, was developed in the seventeenth century but proper calibration and the development of systematic records did not occur until the nineteenth century. The World Meteorological Organization set up a system for collecting temperature measurements on a global scale early in the twentieth century. Data collection and homogenization have become ever more sophisticated. Records from single sites reflect the chaos of the weather, but when combined into regional analyses show distinct trends. North America appears to be a special case, showing a rise in the first half of the twentieth century, a plateau until about 1970, and a subsequent rise. The same patterns can be seen, but not so distinctly, in European records. It is thought that the rises reflect the increasing levels of atmospheric CO2, and the plateau the industrial pollution of the middle of the century. Records from the tropics show the slowest upward trend, but higher latitude records show more pronounced upward trends.

Alkenones are biomarkers produced solely by algae in the order Isochrysidales that have been used to reconstruct sea surface temperature (SST) since the 1980s. However, alkenone-based SST reconstructions in the northern high latitude oceans show significant bias towards warmer temperatures in core-tops, diverge from other SST proxies in down core records, and are often accompanied by anomalously high relative abundance of the C37 tetra-unsaturated methyl alkenone (%C37:4). Elevated %C37:4 is widely interpreted as an indicator of low sea surface salinity from polar water masses, but its biological source has thus far remained elusive. Here we identify a lineage of Isochrysidales that is responsible for elevated C37:4 methyl alkenone in the northern high latitude oceans through next-generation sequencing and lab-culture experiments. This Isochrysidales lineage co-occurs widely with sea ice in marine environments and is distinct from other known marine alkenone-producers, namely Emiliania huxleyi and Gephyrocapsa oceanica. More importantly, the %C37:4 in seawater filtered particulate organic matter and surface sediments is significantly correlated with annual mean sea ice concentrations. In sediment cores from the Svalbard region, the %C37:4 concentration aligns with the Greenland temperature record and other qualitative regional sea ice records spanning the past 14 kyrs, reflecting sea ice concentrations quantitatively. Our findings imply that %C37:4 is a powerful proxy for reconstructing sea ice conditions in the high latitude oceans on thousand- and, potentially, on million-year timescales., Some algae produce compounds called alkenones that can reconstruct sea surface temperature through geological time, but in high latitudes unknown species complicate use of this proxy. Here the authors find a lineage of sea ice algae that produces alkenones and can be used as a paleo-sensor for sea ice abundance.

The Tibetan Plateau (TP) has numerous glaciers that provide water for more than one-third of the world’s population. Reconstructing past temperature change on the TP provides a valuable context for assessing the current and possible future status of glaciers. However, the quantitative paleotemperature records since the last deglaciation on the TP are sparse. Moreover, existing records have revealed a conflicting Holocene temperature variation patterns on the northeastern and western TP. Quantitative temperature records on the central TP would be essential for a better understanding of the spatiotemporal complexity of temperature variation. In this study, we report the temperature record from the sedimentary record of lake Linggo Co on the central TP since the last deglaciation using branched glycerol dialkyl glycerol tetraethers (bGDGTs) based proxy. Our results indicate that the paleoclimate during the last deglaciation on the central TP was characterized by large fluctuations in temperature. The mean annual temperature of lake Linggo Co remained low during the early Holocene (11.7–10 ka BP) and gradually increased to 4 oC at 8.3 ka, rapidly declining to -2 oC on average towards the present day. Solar radiation, continental glacier feedback, as well as atmosphere circulation play a major role in the distribution of sensitive and latent heat, thus affecting the Holocene temperature variability of the TP. Discrepancies in published records on the TP can result from a seasonal bias of the proxies and spatial differences due to topography - boundary effect. Our results suggest that the seasonal bias of proxies, the spatiotemporal difference should be taken into consideration before regional or global synthesis of paleotemperature records.

As European heatwaves become more severe, summers in the United Kingdom (UK) are also getting warmer. The UK record temperature of 38.7 °C set in Cambridge in July 2019 prompts the question of whether exceeding 40 °C is now within reach. Here, we show how human influence is increasing the likelihood of exceeding 30, 35 and 40 °C locally. We utilise observations to relate local to UK mean extremes and apply the resulting relationships to climate model data in a risk-based attribution methodology. We find that temperatures above 35 °C are becoming increasingly common in the southeast, while by 2100 many areas in the north are likely to exceed 30 °C at least once per decade. Summers which see days above 40 °C somewhere in the UK have a return time of 100-300 years at present, but, without mitigating greenhouse gas emissions, this can decrease to 3.5 years by 2100., The United Kingdom has experienced a strong heat wave in 2019 that set a new temperature record for the country of 38.7 °C. In this study the authors show that under climate change, local temperatures are increasingly likely to exceed 35 °C and 40 °C in the next decades and, hence, summers like the one of 2019 become more frequent.

Aim: Catastrophic forest mortality due to more extreme rainfall deficits and higher temperatures under future climate scenarios has been predicted. The aim of this study is to explore the magnitude of historical drought-induced tree mortality under pre-warming conditions. Location: North-eastern Australia. Time period: 1845–2017. Major taxa studied: Trees. Methods: Field survey, historical analysis and climate analysis. Results: We present evidence of 18%–30% tree mortality from recent droughts across three regions of north-eastern Australia with rainfall deficits less severe than earlier historical droughts. The corrected temperature record represents modest warming at the stations with long records in the vicinity of the study areas. In terms of rainfall deficit the most severe drought on record occurred in the early 20th century, and historical evidence confirms that this drought and earlier droughts before the advent of pastoralism coincided with substantial tree mortality. Main conclusions: Dramatic declines in woody biomass in response to drought historically occurred more than once a century and are a natural phenomenon in semi-arid Australia. The magnitude of drought-induced tree mortality under natural climate fluctuations requires further investigation in other continents. Widespread drought-induced tree mortality is not just a recent global change phenomenon and has been underestimated as a natural ecological process. However, even more severe forest die-off events from more extreme hotter droughts are predicted if Earth’s warming proceeds as currently projected.

The long-term cooling or warming trend is one of the most important aspects of Holocene paleoclimatic research. However, there are currently significant discrepancies among climatic simulation results, sedimentary and synthesized Holocene temperature records. These discrepancies call for new Holocene temperature records with a robust chronology and unambiguous indicative significance. Here, we present a ca. 45-year-resolution alpine peat α-cellulose carbon isotopic (δ13C) record from the Altai Mountains in central Asia. The chronology of the record has been well-constrained by 22 AMS 14C dates of the peat α-cellulose samples. Based on detailed modern-process study results, the indicative significance of the record has been carefully determined as summer temperature indicator. The record reveals an overall trend of increasing summer temperature for the past ca. 11 ka with a warmer early (from ca. 8–6 ka BP) and late (from ca. 4–0 ka BP) Holocene and colder middle Holocene (from ca. 6–4 ka BP). The general pattern of a warmer early and late Holocene and colder middle Holocene is consistent with previously reported temperature records from central Asia, the Tibetan Plateau, and North China. The long-term warming trend in our summer temperature record is consistent with recently reported winter temperature records from high latitudes of continental Eurasia. All these results further support the reliability of our summer temperature record from central Asia. The better understandings about the Holocene temperature history and its possible driven mechanism(s) can be benefited potentially from more reliable Holocene temperature records, including our record reported in this paper.

Polar Regions are characterized by extreme weather and climate. The polar meteorology plays a significant role in global climate system. Further, the global warming has generated renewed interest in the study of Polar Regions as the changes in polar and sea-ice extent have widespread implication on atmospheric circulation. India initiated first multi-disciplinary scientific expedition to Antarctica in 1981. The meteorological data are being collected from the very first Indian expedition to Antarctica. The present paper reviews the progress of India's scientific research in polar meteorology. The analysis of 25 years meteorological data collected at Maitri station for the period 1991–2015 is presented in the paper. The observed trend in the temperature data of 19 Antarctic stations obtained from READER project for the period 1991–2015 has also been examined. The 25 years long term temperature record shows cooling over Maitri station. The Maitri station showed cooling of 0.054 °C per year between 1991 and 2015, with similar pronounced seasonal trends. The nearby Russian station Novolazarevskaya also showed a cooling trend of 0.032 °C per year. The trend analysis of other meteorological parameters for the period 1991–2015 is also presented. The Antarctic Peninsula and almost all of West Antarctica showed warming during 1991–2015. The majority of stations in East Antarctica close to the coast show cooling or no significant trend. The analysis also found slight decreasing trend in the pressure over the 1991–2015 time period which is not statistically significant. The wind speed, however, does show a significant declining trend of 0.14 knots/year over the same period.

Despite the fact that the Little Ice Age (LIA) is well documented for the European Alps, substantial uncertainties concerning the regional spatio-temporal patterns of temperature changes associated with the LIA still exist, especially for their eastern sector. Here we present a high-resolution (4–10 years) 700-year long mean July air temperature reconstruction based on subfossil chironomid assemblages from a remote lake in the Austrian Eastern Alps to gain further insights into the LIA climatic deterioration in the region. The record provides evidence for a prolonged period of predominantly cooler conditions during AD 1530–1920, broadly equivalent to the climatically defined LIA in Europe. The main LIA phase appears to have consisted of two cold time intervals divided by slightly warmer episodes in the second half of the 1600s. The most severe cooling occurred during the eighteenth century. The LIA temperature minimum about 1.5 °C below the long-term mean recorded in the mid-1780 s coincides with the strongest volcanic signal found in the Greenland ice cores over the past 700 years and may be, at least in part, a manifestation of cooling that followed the long-lasting AD 1783–1784 Laki eruption. A continuous warming trend is evident since ca AD 1890 (1.1 °C in 120 years). The chironomid-inferred temperatures show a clear correlation with the instrumental data and reveal a close agreement with paleotemperature evidence from regional high-elevation tree-ring chronologies. A considerable amount of the variability in the temperature record may be linked to changes in the North Atlantic Oscillation. Electronic supplementary material The online version of this article (10.1007/s00382-018-4555-y) contains supplementary material, which is available to authorized users.

Paleotemperature reconstructions are essential for distinguishing anthropogenic climate change from natural variability. An emerging method in paleolimnology is the use of branched glycerol dialkyl glycerol tetraethers (brGDGTs) in sediments to reconstruct temperature, but their application is hindered by a limited understanding of their sources, seasonal production, and transport. Here, we report seasonally resolved measurements of brGDGT production in the water column, in catchment soils, and in a sediment core from Basin Pond, a small, deep inland lake in Maine, USA. We find similar brGDGT distributions in both water column and lake sediment samples but the catchment soils have distinct brGDGT distributions suggesting that (1) brGDGTs are produced within the lake and (2) this in situ production dominates the down-core sedimentary signal. Seasonally, depth-resolved measurements indicate that most brGDGT production occurs in late fall, and at intermediate depths (18–30 m) in the water column. We utilize these observations to help interpret a Basin Pond brGDGT-based temperature reconstruction spanning the past 900 years. This record exhibits trends similar to a pollen record from the same site and also to regional and global syntheses of terrestrial temperatures over the last millennium. However, the Basin Pond temperature record shows higher-frequency variability than has previously been captured by such an archive in the northeastern United States, potentially attributed to the North Atlantic Oscillation and volcanic or solar activity. This first brGDGT-based multi-centennial paleoreconstruction from this region contributes to our understanding of the production and fate of brGDGTs in lacustrine systems.

The volume of the Antarctic continental ice sheet(s) varied substantially during the Oligocene and Miocene (∼34–5 Ma) from smaller to substantially larger than today, both on million-year and on orbital timescales. However, reproduction through physical modeling of a dynamic response of the ice sheets to climate forcing remains problematic, suggesting the existence of complex feedback mechanisms between the cryosphere, ocean, and atmosphere systems. There is therefore an urgent need to improve the models for better predictions of these systems, including resulting potential future sea level change. To assess the interactions between the cryosphere, ocean, and atmosphere, knowledge of ancient sea surface conditions close to the Antarctic margin is essential. Here, we present a new TEX86-based sea surface water paleotemperature record measured on Oligocene sediments from Integrated Ocean Drilling Program (IODP) Site U1356, offshore Wilkes Land, East Antarctica. The new data are presented along with previously published Miocene temperatures from the same site. Together the data cover the interval between ∼34 and ∼11 Ma and encompasses two hiatuses. This record allows us to accurately reconstruct the magnitude of sea surface temperature (SST) variability and trends on both million-year and glacial–interglacial timescales. On average, TEX86 values indicate SSTs ranging between 10 and 21 ∘C during the Oligocene and Miocene, which is on the upper end of the few existing reconstructions from other high-latitude Southern Ocean sites. SST maxima occur around 30.5, 25, and 17 Ma. Our record suggests generally warm to temperate ocean offshore Wilkes Land. Based on lithological alternations detected in the sedimentary record, which are assigned to glacial–interglacial deposits, a SST variability of 1.5–3.1 ∘C at glacial–interglacial timescales can be established. This variability is slightly larger than that of deep-sea temperatures recorded in Mg ∕ Ca data. Our reconstructed Oligocene temperature variability has implications for Oligocene ice volume estimates based on benthic δ18O records. If the long-term and orbital-scale SST variability at Site U1356 mirrors that of the nearby region of deep-water formation, we argue that a substantial portion of the variability and trends contained in long-term δ18O records can be explained by variability in Southern high-latitude temperature and that the Antarctic ice volume may have been less dynamic than previously thought. Importantly, our temperature record suggests that Oligocene–Miocene Antarctic ice sheets were generally of smaller size compared to today.

Proxy-based reconstructions of Holocene temperature show that both the timing and magnitude of the thermal maximum varied substantially across different regions. Given the ‘Holocene temperature conundrum’, it is becoming increasingly important to reconstruct seasonal temperature variations. As a major component of the global monsoon system, the Indian summer monsoon (ISM) transports moisture and heat from the tropical oceans to higher latitudes and thus it has substantial socioeconomic implications for its regions of influences. We developed a well-dated, pollen-based summer temperature record (mean July; MJT) for the last 14,000 years from Xingyun Lake in southwest China, where the climate is dominated by the ISM. MJT decreased during the Younger Dryas, increased slowly to high values during 8000–5500 yr BP, and decreased thereafter. The MJT record differs from that inferred using carbonate oxygen isotopes (δ18O) from the same sediment core. The latter record reflects variations in monsoon precipitation, with highest precipitation during the early Holocene (11,000–6500 yr BP). We propose that summer temperature and precipitation in southwest China were decoupled during the early Holocene. Both MJT and monsoon precipitation decreased after the middle Holocene, tracking the trend in boreal summer insolation. We suggest that greater cloud cover, associated with high precipitation and generated by a strong summer monsoon, may have depressed early Holocene temperatures that would otherwise be driven by greater summer insolation. Melting ice sheets in high-latitude regions and high concentrations of atmospheric aerosols during the early Holocene may also have contributed, in part, to the relatively cool summer temperatures.

A considerable amount of research work on climate change is being done to examine what has happened in the recorded past and what might happen throughout the remainder of the 21st Century. While the data for trends in the temperature record tend to be more straightforward, what has and will happen with precipitation change is less clear. However, there is the suggestion that wet places will get wetter and dry places with become more arid.Research by others suggests that extreme daily precipitation amounts in Kansas are trending upward. This research addresses the observational record of change in precipitation seasonality, a little-studied aspect of global climate variability and the related impact on moisture delivery. Monthly precipitation data were summed to provide seasonal totals and seasonal percentages of the annual total were calculated. Using data for the nine Climate Divisions within Kansas for the period from 1895–2014, the results from this analysis indicate that much of Kansas has a winter-dry climate. Over the period of record, there has been a tendency for the spring months of March, April, and May to gain a greater share of the annual total. Geographic variation across the state indicates a west-to-east gradient with greater seasonality in the west and a greater increase in spring and summer precipitation in eastern Kansas.

Long-term, high-resolution temperature records which combine an unambiguous proxy and precise dating are rare in China. In addition, the societal implications of past temperature change on a regional scale have not been sufficiently assessed. Here, based on the modern relationship between chironomids and temperature, we use fossil chironomid assemblages in a precisely dated sediment core from Gonghai Lake to explore temperature variability during the past 4000 years in northern China. Subsequently, we address the possible regional societal implications of temperature change through a statistical analysis of the occurrence of wars. Our results show the following. (1) The mean annual temperature (TANN) was relatively high during 4000–2700 cal yr BP, decreased gradually during 2700–1270 cal yr BP and then fluctuated during the last 1270 years. (2) A cold event in the Period of Disunity, the Sui-Tang Warm Period (STWP), the Medieval Warm Period (MWP) and the Little Ice Age (LIA) can all be recognized in the paleotemperature record, as well as in many other temperature reconstructions in China. This suggests that our chironomid-inferred temperature record for the Gonghai Lake region is representative. (3) Local wars in Shanxi Province, documented in the historical literature during the past 2700 years, are statistically significantly correlated with changes in temperature, and the relationship is a good example of the potential societal implications of temperature change on a regional scale.

Although the contribution of current summer warming to the widespread drying of European peatlands is undeniable, summer temperature fluctuations alone are unable to explain all the hydrological shifts of these ecosystems. We aim to determine whether the current coupling of high summer temperatures and low water tables of peatlands in northern Poland is recent or has been stable over long timescales, and to infer the climatic context driving past relationships between temperature and peatland hydrology. We compare the previously published 4000-year long paleohydrological record from Kusowo bog with a new chironomid-based summer temperature record covering the last 4.5 ka from nearby (~7 km) Lake Spore. Although several simultaneous shifts in our hydrological and temperature reconstructions are evident on multi-decadal to centennial timescales, for instance during the peak cooling of the Migration Period or Little Ice Age (~1.4 and 0.4 cal ka, respectively), the records reveal mostly independent fluctuations. However, the relatively high uncertainty of our quantitative estimates suggests caution is warranted when inferring the strength of the relationship between the reconstructed variables at this temporal resolution. Howeverm, at centennial to millennial timescales, the relationship between the records is surprisingly strong. Overall, warmer summers (mean July temperature = 18.7 °C) before ~2.3 cal. ka corresponded well with lower ground water tables at Kusowo bog (mean = 11.2 cm), whereas cooler summers in the following period (mean = 17.4 °C) were accompanied by higher water tables (mean = 7.9 cm). Particularly wet bog conditions during the last ~0.7 ka were also the coldest. The finding that on long timescales the dring of Kusowo bog coincided with warming suggests a persistent regional climate pattern in which drought conditions change along with summer temperatures. If this millennial-scale pattern holds for the projected warming, further peatland drying can be expected in northern Poland.

This study aims to assess the role of ephemeral snow cover on ground thermal regime and active layer thickness in two ground temperature measurement profiles on the Circumpolar Active Layer Monitoring Network – South (CALM-S) JGM site on James Ross Island, eastern Antarctic Peninsula during the high austral summer 2018. The snowstorm of 13–14 January created a snowpack of recorded depth of up to 38 cm. The snowpack remained on the study site for 12 days in total and covered 46% of its area six days after the snowfall. It directly affected ground thermal regime as indicates temperature record at snow-covered profile AWS-JGM which subsurface section was nearly 5 °C colder compared to the snow-free AWS-CALM profile. The thermal insulation effect of snow cover is also reflected in the mean monthly (January) and summer (DJF) ground temperatures on AWS-JGM that decreased by ca 1.1 and 0.7 °C, respectively. Summer thawing degree days at a depth of 5 cm decreased by ca 10% and active layer was ca 5–10 cm thinner when compared to previous snow-free summer seasons. Surveying by ground penetrating radar revealed a general active layer thinning of up to 20% in those parts of the CALM-S which were covered by snow of >20 cm depth for at least six days.

Tree-ring studies from tropical to subtropical regions are rarer than that from extratropical regions, which greatly limit our understanding of some critical climate change issues. Based on the tree-ring-width chronology of samples collected from the Dabie Mountains, we reconstructed the April–June mean temperature for this region with an explained variance of 46.8%. Five cold (1861–1869, 1889–1899, 1913–1920, 1936–1942 and 1952–1990) and three warm (1870–1888, 1922–1934 and 2000–2005) periods were identified in the reconstruction. The reconstruction not only agreed well with the instrumental records in and around the study area, but also showed good resemblance to previous temperature reconstructions from nearby regions, indicating its spatial and temporal representativeness of the temperature variation in the central part of eastern China. Although no secular warming trend was found, the warming trend since 1970 was unambiguous in the Dabie Mountains (0.064 °C/year). Further temperature comparison indicated that the start time of the recent warming in eastern China was regional different. It delayed gradually from north to south, starting at least around 1940 AD in the north part, around 1970 AD in the central part and around 1980s in the south part. This work enriches the high-resolution temperature reconstructions in eastern China. We expect that climate warming in the future would promote the radial growth of alpine Pinus taiwanensis in the subtropical areas of China, therefore promote the carbon capture and carbon storage in the Pinus taiwanensis forest. It also helps to clarify the regional characteristic of recent warming in eastern China.

We present a Southwest Pacific Ocean paleothermometry transect using new and existing foraminiferal Mg/Ca data from six Eocene locations from eastern New Zealand to southwestern Campbell Plateau, spanning 10° of paleolatitude (43° to 53°S). Sea surface and seafloor temperatures (SST and SFT) have been calculated taking into account the partition coefficients of calcite and Paleogene Mg/Ca sw ratios, and used to determine values for the power component ( H ) of this relationship in foraminiferal calcite from paired proxy (δ 18 O and Mg/Ca) records from Canterbury Basin. This study presents the first Eocene paleotemperature record for the East Coast Basin and, in so doing, shows the absence of a meridional temperature gradient over 10° of latitude during the Early Eocene Climatic Optimum (EECO) and provides evidence for a very weak to absent gradient from the equatorial Pacific to 53°S at this time of extreme global warmth. The application of a new subsurface TEX 86 calibration correlates remarkably well with Mg/Ca seafloor temperature trends from the continental slope setting ( 86 is recording an upper ocean subsurface temperature record, rather than simply SST values. SST-SFT gradients demonstrate a notable reduction, decreasing to 3–5 °C across the EECO. The comparable ocean temperatures of the East Coast Basin, Canterbury Basin and DSDP Site 277 during this time support the intensification of a proto-East Australian Current (EAC), explaining the distribution of tropical sea temperatures extending into the high-latitude Southwest Pacific Ocean during the EECO. Seafloor temperatures (~ 1000 m paleodepth) likely correspond to a northern, intermediate water source during the early Eocene, before switching to a cooler southern-derived source in the middle to late Eocene.

We present a quantitative mean July temperature record spanning the last c. 5000 years from an alpine lake in south-western China. The reconstruction is based on the application of an established chironomid-based inference model using 100 lakes from the region. The reconstructed summer temperature changes are within 2.4°C of modern throughout the record. The results suggest that the summer temperature changes in south-east margin of the Qinghai–Tibetan plateau (QTP) predominantly responds to Asian Summer Monsoon influence, forced by summer insolation until c. 3200 cal. BP. Four cooling events, each separated by c. 500 years (between 3200 and 1600 cal. BP), were observed and these may correspond to the 500-year quasi-periodic solar fluctuation. The most recent cooling period, that is, ‘the Little Ice Age’, appears robust in the Heihai Lake record, providing further evidence that a hemisphere-wide forcing mechanism is possible for this climate event.

Arctic climate has experienced major changes over the past millennia that are not fully understood in terms of their controls and seasonality. Stable isotope data from ice wedges in permafrost provide unique information on past winter climate. Recently, an ice-wedge record from the Lena River Delta suggested for the first time that Siberian winter temperatures increased throughout the Holocene, contradicting most other Arctic palaeoclimate reconstructions which are likely biased towards the summer. However, the representativeness of this single record and the spatial extent of its reconstructed winter warming signal is unclear. Here, we present a new winter temperature record based on paired stable oxygen (δ18O) and radiocarbon age data spanning the last two millennia from the Oyogos Yar coast in northeast Siberia. The record confirms the long-term winter warming signal as well as the unprecedented temperature rise in recent decades. This confirmation demonstrates that winter warming over the last millennia is a coherent feature in the northeastern Siberian Arctic, supporting the hypothesis of an insolation-driven seasonal Holocene temperature evolution followed by a strong warming likely related to anthropogenic forcing.

We present a high-resolution geochemical and grain-size record from a Holocene sediment core off the Pangani River mouth, Tanzania. Elemental ratios between biogenic elements and Al (i.e., Ca/Al, Mg/Al, and Sr/Al) are mainly influenced by terrigenous dilution on carbonate concentration and/or limitation of carbonate production as a result of variations in the supply of fine-grained terrigenous sediments of the Pangani River. Such elemental ratios increased significantly at the end of the mid-Holocene between 5 and 3.5 ka, demonstrating a gradual transition from the humid early and mid-Holocene to the arid late Holocene in East Africa. Among the elemental ratios between terrigenous elements and Al, Si/Al and K/Al ratios correlate to grain-size variation, indicating a change in sedimentation regime. Fe/Al and Ti/Al ratios show that the sediment source area has shifted from the terrestrial volcanic region of Tanzania (Fe, Ti rich) to the coastal and inner-shelf regions (Fe, Ti poor) around 7.5 ka, in response to arid climate and high sea level. Our geochemical results correspond with a sea-surface temperature record derived from the same sediment core, indicating that the end of the East African Humid Period could have been gradual and related to the cooling water in the western Indian Ocean.

[EN]The geothermal resources in Spain have been a source of deep research in recent years and are, in general, well-defined. However, there are some areas where the records from the National Institute for Geology and Mining show thermal activity from different sources despite no geothermal resources being registered there. This is the case of the area in the south of the Duero basin where this research was carried out. Seizing the opportunity of a deep borehole being drilled in the location, some geophysical resources were used to gather information about the geothermal properties of the area. The employed geophysical methods were time-domain electromagnetics (TDEM) and borehole logging; the first provided information about the depth of the bedrock and the general geological structure, whereas the second one gave more detail on the geological composition of the different layers and a temperature record across the whole sounding. The results allowed us to establish the geothermal gradient of the area and to discern the depth of the bedrock. Using the first 200 m of the borehole logging, the thermal conductivity of the ground for shallow geothermal systems was estimated.

High-quality paleoclimate reconstructions can provide crucial climate context to test the hypothesis of climatic impact on historical culture changes. Here we report high-resolution and quantitative temperature and precipitation records covering the entire “5000-year” Chinese history in northern China. Our temperature record shows a slight decrease before 1800 cal yr BP and a ∼4 °C rapid cooling afterwards, superimposed with four major ∼2–3 °C centennial-scale cold events, potentially corresponding to the widespread North Atlantic ice-rafted debris Bond events. While precipitation record shows high value before 3000 cal yr BP, and a gradual decrease of ∼250 mm with two distinct ∼100 mm centennial-scale dry intervals after 1100 cal yr BP. Our data not only provide a more complete climate background for Chinese dynasties, but show the coincidence in the timing between abrupt cold and/or dry events and large-scale social unrests and southern migration of nomads. This finding reveals climate fluctuations, in particular variations in temperature, played an important role in affecting Chinese historical cultural changes.

Coral skeletons are valuable archives of past ocean conditions. However, interpretation of coral paleotemperature records is confounded by uncertainties associated with single element-ratio thermometers, including Sr/Ca. A new approach, Sr-U, uses U/Ca to constrain the influence of Rayleigh fractionation on Sr/Ca [DeCarlo et al., 2016]. Here, we build on the initial Pacific Porites Sr-U calibration to include multiple Atlantic and Pacific coral genera from multiple coral reef locations spanning a temperature range of 23.15-30.12 °C. Accounting for the wintertime growth cessation of one Bermuda coral, we show that Sr-U is strongly correlated with the average water temperature at each location (r2 = 0.91, P

To establish precise climate trend analyses, highly reliable and accurate homogenous historical climate data are required. To this end, we undertake a robust quality control and homogenization process of daily Tmax and Tmin data (1916–2013) for the Western Cape Province, South Africa, using RClimDex, ProClimDB and Anclim software. Inhomogeneities were detected using the pairwise method in AnClim, suggesting possible artificial shifts in the time series. The adjustment of time series utilized ProClimDB software to create reference series using highly correlated or nearest neighbour stations. Given few available long-term data sets, the study is limited to eight suitable stations. The modified Mann Kendall test in XLSTAT 2015 software identified annual and seasonal trends in the newly homogenized monthly Tmax and Tmin data. Annual Tmax and Tmin adjusted data over the Western Cape region indicate statistically significant increasing temperature trends over the period 1916–2013, with the exception of an insignificant decreasing Tmax trend at Cape St Blaize. A statistically significant increasing trend (0.13 °C/decade) for all stations used in this study is recorded for the common period 1937–2001. The seasonal trends also support significant increasing trends, with the exception of Tmax trends for summer (−0.03 °C/decade) and autumn (0 °C/decade) at Kirstenbosch.

Since the 1950s, research stations on the Antarctic Peninsula have recorded some of the largest increases in near-surface air temperature in the Southern Hemisphere1. This warming has contributed to the regional retreat of glaciers2, disintegration of floating ice shelves3 and a ‘greening’ through the expansion in range of various flora4. Several interlinked processes have been suggested as contributing to the warming, including stratospheric ozone depletion5, local sea-ice loss6, an increase in westerly winds5, 7, and changes in the strength and location of low–high-latitude atmospheric teleconnections8, 9. Here we use a stacked temperature record to show an absence of regional warming since the late 1990s. The annual mean temperature has decreased at a statistically significant rate, with the most rapid cooling during the Austral summer. Temperatures have decreased as a consequence of a greater frequency of cold, east-to-southeasterly winds, resulting from more cyclonic conditions in the northern Weddell Sea associated with a strengthening mid-latitude jet. These circulation changes have also increased the advection of sea ice towards the east coast of the peninsula, amplifying their effects. Our findings cover only 1% of the Antarctic continent and emphasize that decadal temperature changes in this region are not primarily associated with the drivers of global temperature change but, rather, reflect the extreme natural internal variability of the regional atmospheric circulation.

The effectiveness of multiple linear regression approaches in removing solar, volcanic, and El Nino Southern Oscillation (ENSO) influences from the recent (1979–2012) surface temperature record is examined, using simple energy balance and global climate models (GCMs). These multiple regression methods are found to incorrectly diagnose the underlying signal – particularly in the presence of a deceleration – by generally overestimating the solar cooling contribution to an early 21st century pause while underestimating the warming contribution from the Mt. Pinatubo recovery. In fact, one-box models and GCMs suggest that the Pinatubo recovery has contributed more to post-2000 warming trends than the solar minimum has contributed to cooling over the same period. After adjusting the observed surface temperature record based on the natural-only multi-model mean from several CMIP5 GCMs and an empirical ENSO adjustment, a significant deceleration in the surface temperature increase is found, ranging in magnitude from −0.06 to −0.12 K dec−2 depending on model sensitivity and the temperature index used. This likely points to internal decadal variability beyond these solar, volcanic, and ENSO influences.

During the Late Palaeogene between ~40 and 23 million years ago (Ma), Earth transitioned from a warm non-glaciated climate state and developed large dynamic ice sheets on Antarctica. This transition is largely inferred from the deep-sea oxygen isotope record because records from independent temperature proxies are sparse. Here we present a 25-million-year-long alkenone-based record of surface temperature change from the North Atlantic Ocean. Our long temperature record documents peak warmth (~29 °C) during the middle Eocene, a slow overall decline to the Eocene/Oligocene transition (EOT, ~34 Ma) and high-amplitude variability (between ~28 and 24 °C) during the Oligo–Miocene. The overall structure of the record is similar to that of the deep-sea record, but a distinct anomaly is also evident. We find no evidence of surface cooling in the North Atlantic directly coinciding with the EOT when Antarctica first became cold enough to sustain large ice sheets and subantarctic waters cooled substantially. Surface ocean cooling during the EOT was therefore strongly asymmetric between hemispheres. This transient thermal decoupling of the North Atlantic Ocean from the southern high latitudes suggests that Antarctic glaciation triggered changes in ocean circulation-driven heat transport and influenced the far-field climate response.

Long records of phenological observations are commonly used as data in global change and palaeoclimate research and to analyse plants' responses to climatic changes. Here we delve into the historical archives of plant phenological observations (1750–1875) compiled and published previously by Professor Adolf Moberg (Imperial Alexander University of Finland). The digitized dataset represents 44,487 observations of 450 different plant species for their 15 different phenological phases made in 193 sites across Finland, and results in 662 different phenological variables. The five most frequently observed variables are the blooming of rye, the sowing of barley, the blooming of bird cherry, the leaf outbreak of birch, and the sowing of oat. The spring and summer observations demonstrate positive relationships between the onset date and the site latitude, this relationship becoming negative for observations made in the autumn. This latitudinal effect is evident in the raw data as demonstrated by the temporal correlations between the unadjusted mean phenological records and the mean latitude of the sites. After the latitudinal effect is removed from the original data such correlations are much reduced and the new set of phenological records based on the adjusted dates can be computed. The resulting mean phenological records correlate negatively and statistically significantly with the mean temperatures from April through July. Linear trends indicate (i) summer onsets having become delayed by more than one week over the full period and (ii) shortening of the growing seasons since 1846. The dataset is made available in an open repository.

In central Siberia, past temperature changes have been driving permafrost warming in a region with large organic carbon reserves stored in the perennially frozen ground. However, local arctic temperature histories in the ice-rich permafrost areas of the remote Russian Arctic are sparsely known or based on proxy data with potential seasonal biases and underrepresented in circum-Arctic reconstructions. This study employed two inversion schemes (particle swarm optimization and a least-square method) to reconstruct temperature histories for the past 200–300 years in the Laptev Sea region from two permafrost borehole temperature records. These data were evaluated against larger scale reconstructions from the region. Distinct differences between the western Laptev Sea and the Lena Delta sites were recognized, such as a transition to warmer temperatures a century later in the western Laptev Sea as well as a peak in warming 3 decades later. The local permafrost surface temperature history at Sardakh Island in the Lena Delta was reminiscent of the circum-Arctic regional average trends. However, Mamontov Klyk in the western Laptev Sea was consistent to Arctic trends only in the most recent decade and was more similar to northern hemispheric mean trends. Both sites are consistent with a rapid recent warming that is of synoptic scale. Different environmental influences such as synoptic atmospheric circulation and sea ice may be responsible for differences between the sites. The shallow permafrost boreholes provide missing well-resolved short-scale temperature information in the coastal permafrost tundra of the Arctic. As local differences from circum-Arctic reconstructions, such as later warming and higher warming magnitude, were shown to exist in this region, our results provide a basis for local surface temperature record parameterization of climate models, and in particular of permafrost models.

A continuous 305-year (1711–2016) monthly rainfall series is created for the Island of Ireland. Two overlapping data sources are employed: i) a previously unpublished UK Meteorological Office note containing annual rainfall anomalies and corresponding proportional monthly totals based on weather diaries and early observational records for the period 1711–1977 and; ii) a long-term, homogenised monthly rainfall series for the island of Ireland for the period 1850–2016. Using estimates of long-term average precipitation from the homogenised series to merge these sources, the new 305-year record is constructed and insights drawn about notable extremes, climate variability and change. The consistency of the resulting series was evaluated by comparison with independent long-term observations and reconstructions of precipitation, temperature and circulation indices from across the British-Irish Isles. Strong decadal consistency is evident throughout the record amongst all series in spring, summer and autumn. The winter series is probably too dry from the 1740s to the 1780s, but strong consistency with other records strengthens confidence from 1790 onwards. The new Island of Ireland series reveals remarkably wet winters during the 1730s, concurrent with a period of strong westerly airflow, glacial advance throughout Scandinavia and near unprecedented warmth in the Central England Temperature record – all consistent with the strong phase of the North Atlantic Oscillation. The driest winter decade in the series coincides with the Laki eruption of 1783–1784. Unusually wet summers occurred in the 1750s, consistent with proxy (tree-ring) reconstructions of summer precipitation in the region. In the annual series, the most recent decade (2006–2015) is found to be the wettest in over 300 years. The new series reveals statistically significant (0.05 level) multi-centennial trends in winter (increasing) and summer (decreasing) seasonal precipitation. However, given uncertainties in the early winter record, the former should be treated as tentative. Importantly, we show that the years 1940 to present – the period with the most widely available digitised records – is unrepresentative of long-term changes in all seasons. Although there are recognized uncertainties in the early record, the derived series offers valuable insights for understanding multi-decadal and centennial rainfall variability in Ireland, and provides a firm basis for benchmarking other long-term records and future reconstructions.

This review summarises landform records and published age-estimates (largely based upon tephrochronology) to provide an overview of glacier fluctuations upon the Kamchatka Peninsula during the Holocene and, to a lesser degree, earlier phases of glaciation. The evidence suggests that following deglaciation from the Last Glacial Maximum (LGM), the peninsula experienced numerous phases of small-scale glacial advance. During the Late Glacial, moraine sequences appear to reflect the former presence of extensive glaciers in some parts of the peninsula, though little chronological control is available for deposits of this period. During the Holocene, the earliest and most extensive phase of advance likely occurred sometime prior to c. 6.8 ka, when glaciers extended up to 8 km beyond their current margins. However, these deposits lack maximum age constrains, and pre-Holocene ages cannot be discounted. Between c. 6.8 ka and the onset of ‘Neoglaciation’ c. 4.5 ka, there is little evidence of glacial advance upon the peninsula, and this period likely coincides with the Holocene climatic optimum (or ‘hypsithermal’). Since c. 4.5 ka, numerous moraines have been deposited, likely reflecting a series of progressively less extensive phases of ice advance during the Late Holocene. The final stage of notable ice advance occurred during the Little Ice Age (LIA), between c. 1350 and 1850 C.E., when reduced summer insolation in the Northern Hemisphere likely coincided with solar activity minima and several strong tropical volcanic eruptions to induce widespread cooling. Following the LIA, glaciers upon the peninsula have generally shown a pattern of retreat, with accelerated mass loss in recent decades. However, a number of prominent climatically and non-climatically controlled glacial advances have also occurred during this period. In general, there is evidence to suggest that millennial scale patterns in the extent and timing of glaciation upon the peninsula (encompassing much of the last glacial period) are governed by the extent of ice sheets in North America. Millennial-to-centennial scale fluctuations of Kamchatkan glaciers (encompassing much of the Holocene) are governed by the location and relative intensity of the Aleutian Low and Siberian High pressure systems. Decadal scale variations in glacier extent and mass balance (particularly since the LIA) are governed by inter-decadal climatic variability over the North Pacific (as reflected by the Pacific Decadal Oscillation), alongside a broader trend of hemispheric warming.

High-resolution records of calibrated proxy data for the past millennium are fundamental to place current changes into the context of pre-industrial natural forced and unforced variability. Although the need for regional spatially-explicit comprehensive reconstructions is widely recognized, the proxy data sources are still scarce, particularly for the Southern Hemisphere and especially for South America. We present a 600-year long warm season temperature record from varved sediments of Lago Plomo, a proglacial lake of the Northern Patagonian Ice field in Southern Chile (46°59′S, 72°52′W, 203 m a.s.l.). The thickness of the bright summer sediment layer relative to the dark winter layer (measured as total brightness; % reflectance 400–730 nm) is calibrated against warm season SONDJF temperature (1900–2009; r = 0.58, p (aut) = 0.056, RE = 0.52; CE = 0.15, RMSEP = 0.28 °C; five-year triangular filtered data). In Lago Plomo, warm summer temperatures lead to enhanced glacier melt and suspended sediment transport, which results in thicker light summer layers and to brighter sediments. Although Patagonia shows pronounced regional differences in decadal temperature trends and variability, the 600 years temperature reconstruction from Lago Plomo compares favourably with other regional/continental temperature records, but also emphasizes significant regional differences for which no data and information existed so far. These regional differences seem to be real as they are also reflected in modern climate data sets (1900–2010). The reconstruction shows pronounced subdecadal – multidecadal variability with cold phases during parts of the Little Ice Age (16th and 18th centuries) and in the beginning of the 20th century. The most prominent warm phase is the 19th century which is as warm as the second half of the 20th century. The exceptional summer warmth AD 1780–1810 is also found in other archives of Northern Patagonia and Central Chile. Our record shows the delayed 20th century warming in the Southern Hemisphere. The comparison between winter precipitation and summer temperature (inter-seasonal coupling) from Lago Plomo reveals alternating phases with parallel and contrasting decadal trends of winter precipitation and summer temperature (positive and negative running correlations R winter PP; summer TT ). This observation from the sediment proxy data is also confirmed by two sets of reanalysis data for the 20th century. Reanalysis data show that phases with negative correlations between winter precipitation and summer temperature (e.g., dry winters and warm summers) at Lago Plomo are characteristic for periods when circumpolar Westerly flow is displaced southward and enhanced around 60°S.

The long‐chain diol index (LDI) is a new organic sea surface temperature (SST) proxy based on the distribution of long‐chain diols. It has been applied in several environments but not yet in subpolar regions. Here we tested the LDI on surface sediments and a sediment core from the Sea of Okhotsk, which is the southernmost seasonal sea ice‐covered region in the Northern Hemisphere, and compared it with other organic temperature proxies, that is, U37k′ and TEXL 86. In the surface sediments, the LDI is correlated with autumn SST, similar to the U37k′ but different from the TEXL 86 that correlates best with summer sea subsurface temperature. Remarkably, the obtained local LDI calibration was significantly different from the global core‐top calibration. We used the local LDI calibration to reconstruct past SST changes in the central Sea of Okhotsk. The LDI‐SST record shows low glacial (Marine Isotope Stage, MIS 2, 4, and 6) and high interglacial (MIS 1 and MIS 5) temperatures and follows the same pattern as the U37k′‐SST and a previously published TEXL 86 temperature record. Similar to the modern situation, the reconstructed temperatures during the interglacials likely reflect different seasons, that is, summer for the TEXL 86 and autumn for U37k′ and LDI. During glacials, the reconstructed temperatures of all three proxies are similar to each other, likely reflecting summer temperatures as this was the only season free of sea ice. Our results suggest that the LDI is a suitable proxy to reconstruct subpolar seawater temperatures., Key Points This study discusses the lipid‐based sea temperature reconstructions of the central Sea of OkhotskThe LDI reflects autumn sea surface temperature in core topsDuring glacial stages Uk′ 37, TEXL 86, and LDI reflect summer sea temperature

The relationship between climate and radial tree growth is traditionally used to reconstruct past climate conditions based on interannual tree-ring variations. However, few studies have used these climate-growth relationships to model the radial tree growth based on future climate projections. To detect the future forest dynamics, the climate-induced tree growth from 2006 to 2100 was projected using temperature changes under representative concentration pathway (RCP) 2.6 for the southeastern Tibetan Plateau. Radial tree growth was mainly controlled by annual mean temperature in this region. Based on the relationship between regional annual mean temperature and radial tree growth, a regression model was built that explained 62.5% of variance in the observed temperature record over the period 1911–2005. A period of unprecedented radial tree growth was found after 1998 when compared with the tree growth in the past 700 years. We found that radial tree growth would increase in the period 2006–2045 and decline after that period due to the projected temperature decrease. As forest productivity and biomass are expected to increase with the increased tree growth, these results suggest that temperature-limited systems could see future increases in productivity as growth limitations are lessened. The results of this research could be used to predict regional forest dynamics in the future.

The study of climate of Antarctica and its role in the Earth system is critically important as the region experiences change that has global implications. The climate of the continent and the surrounding ocean are closely coupled to other parts of the global environment by the ocean and the atmosphere. Subjects of immediate interest are forecasting of weather and climate and understanding the effects and likely impacts of climate change. India Meteorological Department is taking part in Indian Scientific Expeditions to Antarctica since the very first expedition during 1981-82. The meteorological data collected at Maitri station for the period 1990-2015 have been analyzed. The long term analysis of temperature record showed a cooling trend at Maitri station. The trend analysis of pressure, wind and blizzards during the period 1990-2015 is also discussed. Recently, the India Meteorological Department has established manned permanent meteorological observatory at Bharati station with the objective to collect data on meteorological parameters, solar radiation and ozone so as to understand the Antarctic atmospheric processes and dynamics. WMO has enlisted Meteorological Observatory at Bharati, and assigned WMO Index number 89776. A GPS-based ozonesonde system has also been installed at Bharati for measurement of vertical profile of ozone. IMD provides weather forecast of Maitri and Bharati stations.

Due to their effects on snow/ice melting in mountains and evaporation in basins, temperature variations are an important influence on the hydrological cycle and water resources in arid Central Asia (ACA). We present independently-dated peat brGDGTs-based MBT′/MBT′5ME records from an alpine Sahara sand peatland (SSP) in the southern Altai Mountains, in ACA. During the past ~11 kyr, the SSP MBT′ and MBT′5ME profiles exhibit consistently increasing trends and they are significantly positively correlated. Using a global peat-specific MBT′5ME-tempeature calibration, the long-term Holocene warming trend indicated by the quantitative SSP mean annual temperature (MATpeat) reconstruction is supported by the peat α-cellulose δ13C summer temperature record from the SSP, and by an independent peat α-cellulose δ18O winter temperature record from a nearby site (i.e. temporal validation). The increasing trends are also evident in Holocene peat MBT′ records from the Hongyuan (HY) peatland in the NE Tibetan Plateau, and in the Shuizhuyang (SZY) peatland in SE China. Notably, both the MBT′ data of the surface samples and the averaged MBT′ data of the Holocene peat cores are consistent with the modern spatial temperature gradient at the SSP, HY and SZY (i.e. spatial validation). This evidence demonstrates the temperature significance of peat MBT′/MBT′5ME records. The long-term Holocene warming trend indicated by the SSP MBT′/MBT′5ME records is supported by recently-acquired Holocene temperature records from the Eurasian continent. This trend is the opposite to the traditional viewpoint of a long-term Holocene cooling trend, and it indicates that more effort is needed to obtain a reliable Holocene temperature history.

It is widely documented that the Earth’s surface temperatures have increased in recent decades. However, temperature increment patterns are not uniform around the globe, showing different or even contrasting trends. Here we present a mean maximum summer temperature record, based on tree-ring widths, over the past 5682 years (3672BC e 2009AD) for southern South America (SSA), covering from mid-Holocene to the present. This is the longest such record for the Southern Hemisphere (SH), and expands available annual proxy climate records for this region in more than 2060 years. Our record explains 49% of the temperature variation, and documents two major warm periods between 3140 e2800BC and 70BC e 150AD, which coincide with the lack of evidence of glacier advances in SSA. Recent decades in the reconstruction (1959e2009) show a warming trend that is not exceptional in the context of the last five millennia. The long-term relationship between our temperature reconstruction and a reconstructed total solar irradiance record, with coinciding cycles at 293, 372, 432e434, 512 and 746 years, indicate a persistent influence of solar forcing on centennial climate variability in SSA. At interannual to interdecadal scales, reconstructed temperature is mainly related to the internal climate variability of the Pacific Ocean, including El Nino Southern Oscillation (ENSO) and longer oscillations. Our ~ study reveals the need to characterize regional-scale climate variability and its drivers, which in the context of global-scale processes such as anthropogenic warming, interact to modulate local climate affecting humans and ecosystems. Fil: Lara, Antonio. Center for Climate and Resilience Research; Chile. Universidad Austral de Chile; Chile. Fundación Centro de los Bosques Nativos; Chile Fil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Urrutia Jalabert, Rocío. Center for Climate and Resilience Research; Chile. Instituto Forestal; Chile. Universidad Austral de Chile; Chile Fil: González Reyes, Álvaro. Center for Climate and Resilience Research; Chile. Universidad Austral de Chile; Chile. Universidad Mayor; Chile Fil: Aravena, Juan Carlos. Universidad de Magallanes; Chile Fil: Luckman, Brian Henry. Western University; Canadá Fil: Cuq, Emilio. Universidad Austral de Chile; Chile Fil: Rodríguez, Carmen Gloria. Universidad Austral de Chile; Chile Fil: Wolodarsky Franke, Alexia. Cooperativa Calahuala; Chile

The paper presents a combined analysis of results from field measurements and numerical simulations aimed at supporting the reconstruction of the temperature time series of the city of Trento in the Alps. This project is challenging, due to various relocations of the observational sites and the increasing effects of urbanisation. Identical temperature sensors were placed at the historical observational sites of the city, to detect systematic differences between these places under various seasonal patterns and weather conditions. However, since differences measured nowadays may not be representative of those occurring in the past, numerical simulations were also run with the WRF model, using a historical land use. Furthermore simulations with the present land use were performed and validated against the observations carried out during the field campaign. The comparison between “present” and “historical” simulations suggests that temperature differences between the sites more embedded in the urban area have not changed significantly from the past, whereas greater modifications have occurred at a location on the valley slope, progressively incorporated into the city. Moreover it is shown that the progressive urbanisation has played a significant role in Trento’s temperature record, the effect being more significant under sunny conditions, when the UHI is stronger.

Extreme event attribution studies can provide valuable information for assessing the risks and costs of future climate change. However, the utility of such information for adaptive decision-making depends on reliable information being provided in a timely manner. Here, we present pre-computed Fraction of Attributable Risk (FAR) tables for various Australian temperature records, as an estimate of the change in likelihood of exceeding defined temperature thresholds that can be attributed to anthropogenic influences, such as long-lived greenhouse gases. Australian and State-based area-average mean, maximum and minimum temperature anomalies are considered. The likelihoods of extreme annual, seasonal and monthly temperatures occurring in a suite of Coupled Model Intercomparison Project phase 5 (CMIP5) simulations incorporating only natural forcings (solar and volcanic aerosols) are compared with the likelihoods from simulations including both natural and anthropogenic (greenhouse gases, aerosols and ozone) forcings. This approach provides a simple tool for the timely assessment of the contribution of anthropogenic factors to record-setting temperatures for different Australian regions. In the case when an existing national or State-wide temperature record is exceeded, the FAR 'look-up' data tables presented here provide an immediate source of information about the change in risk of such an event occurring that can be attributed to anthropogenic influences. In all regions, the FAR values demonstrate that the likelihood of warmer conditions on various timescales has increased due to anthropogenic forcings. The FAR values presented here will be most useful if updated to reflect future changes in anthropogenic forcings and using new record-setting temperature anomalies.

Since the groundbreaking survey of Budapest’s urban climate in 1974, litt le has been done to reveal how the summer heat island of the city has changed. During the last couple of decades, the impact of the anthropogenic heat release due to the spectacular expansion of automobile traffi c and the widespread use of air conditioners may have added an estimated 1–1.5 °C to the temperature surplus of the city. As an evidence of the large-scale climate change, the homogenized temperature record of Budapest shows a strongly growing frequency and persistence of severe heat waves plaguing city dwellers. Regional models predict rising temperatures with more pronounced summer warming until 2100 in the Carpathian Basin. Therefore, the cooler local climates of the Danube islands and the Budai Hills should be appreciated as valuable environmental assets to be saved by more reasonable land use policies and stricter property development regulations.

Increasing interest in global climate change has led to attempts to understand and quantify the relationship between chemical weathering processes and environmental conditions, especially climate. This interest necessitates the identification of new climate proxies for the reconstruction of two important Earth surface processes: physical erosion and chemical weathering. In this study, an AMS C-14-dated 2.8-m-long sediment core, GH09B1, from Lake Gonghai in north-central China was subjected to detailed geochemical analyses to evaluate the intensity of chemical weathering conditions in the catchment. Multivariate statistical analysis of major and trace elemental data of 139 subsamples revealed that the first principal component axis PCA1 explained approximate to 53% of the variance in the assemblage of elements/oxides with significant positive correlations between PCA1 scores and the separation of mobile and soluble elements/oxides from the immobile and resistant elements/oxides, which is thus able to indicate the chemical weathering in the catchment. These results are supported by the down-core trends of other major and trace elemental ratios of chemical weathering intensity as well as by pollen data from the same core. Variations in PCA1, chemical index of alteration (CIA), Rb/Sr ratio and other oxides ratios indicate stronger chemical weathering due to a wet climate during the Medieval Warm Period (MWP). However, the MWP was interrupted by an interval of relatively weaker chemical weathering conditions from AD 940-1070. Weak chemical weathering under a dry climate occurred during the Little Ice Age (LIA), and increased chemical weathering intensity during the Current Warm Period (CWP). Our proxy records of chemical weathering over the last millennium correlate well with the available proxy records of precipitation from Gonghai Lake as well as with the speleothem oxygen isotope record from Wanxiang Cave, but do not show a significant correlation with the temperature record in N China, suggesting that the chemical weathering intensity in the study area was mainly controlled by the amount of rainfall rather than by temperature. We conclude that high resolution lacustrine sediment geochemical parameters can be used as reliable proxies for climate variations at centennial-decadal time scales.

There is increasing evidence that accelerated warming at high-latitudes is associated with increased climate variability at mid-latitudes, including the frequency and intensity of storms. However, due to short instrumental records our understanding of how ocean-atmosphere dynamics operate during warmer than present climates remains limited. Here we present a palaeoceanographic investigation of the transition between the middle Holocene intervals of the Northgrippian (8.2–4.2 ka) and the late Holocene interval of the Meghalayan (4.2–0 ka) to test the hypothesis of an eastward shift of the Icelandic Low under warmer than present climate scenarios. Reconstructions of bottom water temperatures (BWT) and stable oxygen isotopes (Mg/Ca, δ18O) using the benthic foraminifera Hyalinea balthica reveal warmer than present BWT of up to 2.6 ± 0.7 °C on the Irish Continental Shelf until circa 4.2 ka. The results suggest that Atlantic waters of subtropical origins were more prevalent in the eastern subpolar gyre (SPG) and on the Irish Continental Shelf. We link this oceanographic signature to an eastward shift of the Icelandic Low. We then place our local temperature record into an extra-regional context, using a combination of modern observations and existing palaeo datasets, which enables us to assess the impact of changing atmospheric modes on ocean-atmosphere climate linkages within the North Atlantic Region. The enhanced influence of warm subtropical Atlantic waters recirculating along the boundaries of the SPG under this scenario, would potentially have enhanced melt rates of marine-terminating glaciers on the east Greenland Shelf during the Northgrippian.

Maximum and minimum daily temperatures from the second half of the 20th century are examined using a high resolution dataset of 833 grid cells across the state of Florida. A bivariate Extreme Value Analysis Point Process approach is used to model characteristics including the frequency, magnitude, duration, and timing of periods or heat waves during which both daily maximum and minimum temperatures exceed their respective 90th percentile thresholds. Variability in heat wave characteristics is examined across the state to give an indication of those areas where heat waves with certain characteristics may be more likely to occur. Changes in heat wave characteristics through time are examined by halving the temperature record and determining changes to heat wave characteristics between the two periods. This exploration of changes in heat wave risk through time gives a possible suggestion of trends in future heat wave risk. Findings indicate that there is considerable spatial variability in heat wave characteristics although heat waves have become increasingly frequent and intense throughout much of the state.