Changes In Surface Air Temperature Research Articles

Temporal and spatial variations of the air temperature in the Taklamakan Desert and surrounding areas

In recent years, climate change has attracted many researchers’ attention around the world, among which the analysis of long-term surface air temperature (SAT) changes is essential. In this paper, we analyze the spatial and temporal variations of the SAT in Tarim Basin from 1961 to 2015. Our results show that warming of the SAT is evident at most weather stations in the Taklamakan Desert, except for those at Aketao, Kuche, and Tazhong. The overall warming rate is 0.25 °C/decade in the Taklamakan Desert. Mann–Kendall tests are adopted to detect abrupt changes in the SATs. It is demonstrated that nine out of 39 stations experienced a simultaneous abrupt change in 1996, which is consistent with the abrupt changes seen in the local vegetation cover. The relationships between the SAT changes and the underlying landscape and vegetation cover are also discussed in this paper. A moderate negative correlation is discovered between the SAT and the normalized difference vegetation index (NDVI) at oases.

Optimized design and experimental validation of a temperature sensor for surface air temperature observation

The rate of global surface air temperature change is approximately 0.2 ± 0.1 ºC per decade. However, existing temperature sensors may produce a radiation error that is on the order of 1 ºC due to the effects of direct solar radiation, reflected radiation, diffuse radiation, upwelling long-wave radiation, etc. To reduce this radiation error, a temperature sensor with an airflow guide device is designed. First, a computational fluid dynamics (CFD) method is employed to optimize this sensor. Then, the CFD method is used to quantify the radiation errors for the optimal sensor under different environmental conditions. Next, to further improve the measurement accuracy, a radiation error correction equation is obtained by using an extreme learning machine (ELM) method. Finally, to verify the observation accuracy of this sensor and the correction accuracy of this correction equation, a radiation error experiment platform is used to conduct observation experiments. A 076B aspirated temperature sensor served as a temperature reference. The mean absolute error, root mean square error and correlation coefficient between the radiation errors provided by the correction equation and the radiation errors provided by the experiments are 0.069 ºC, 0.056 ºC and 0.811, respectively.

The impact of atmospheric moisture transport on winter Arctic warming: Radiation versus latent heat release

AbstractAtmospheric moisture transport (AMT) contributes significantly to the recent accelerated Arctic warming. However, the impact of AMT has not been well quantified, not to mention the relative contribution of its impact on microphysical latent heating (LAH) and longwave radiative heating (LWH). A series of Polar‐WRF model experiments with different magnitudes of AMT are conducted to study the response of winter Arctic temperature to AMT variations. Results show that atmospheric precipitable water is very sensitive to AMT variations and thus can define the changes in surface air temperature by altering surface downward longwave radiation. Additionally, because evaporation and sublimation tend to balance the AMT‐induced moisture changes near the surface, LWH in the lower troposphere is determined by downward longwave radiation and thus can be the dominant factor for temperature variations. However, temperature in the mid‐ and upper troposphere is primarily determined by changes in LAH, because the content of ice‐phase cloud aloft is significantly affected by AMT. In addition, the changes in LWH in the mid‐ and upper troposphere are governed by upward longwave radiation, thus offsetting some of the temperature variations. These findings have implications for the attribution of Arctic current warming and the prediction of its future temperature change.

Multi-Aspect Assessment of CMIP6 Models for Arctic Sea Ice Simulation

AbstractThis paper evaluates the ability of 35 models from phase 6 of the Coupled Model Intercomparison Project (CMIP6) to simulate Arctic sea ice by comparing simulated results with observation from the aspects of spatial patterns and temporal variation. The simulation ability of each model is also quantified by the Taylor score and e score from these two aspects. Results show that biases between observed and simulated Arctic sea ice concentration (SIC) are mainly located in the East Greenland, Barents, and Bering Seas and the Sea of Okhotsk. The largest difference between the observed and simulated SIC spatial patterns occurs in September. Since the beginning of the twenty-first century, the ability of most models to simulate summer SIC spatial patterns has decreased. We also find that models with the Sea Ice Simulator (SIS) sea ice component in CMIP6 show a consistent larger positive simulation biases of SIC in the East Greenland and Barents Seas. In addition, for most models, the higher the model resolution is, the better the match between the simulated and observed spatial patterns of winter Arctic SIC is. Furthermore, this paper makes a detailed assessment for temporal variation of Arctic sea ice extent (SIE) with regard to climatological average, seasonal SIE, multiyear linear trend, and detrended standard deviation of SIE. The sensitivity of September Arctic SIE to a given change of Arctic surface air temperature over 1979–2014 in each model has also been investigated. Most models simulate a smaller loss of September Arctic SIE per degree of warming than is observed (1.37 × 106 km2 K−1).

Future Precipitation Extremes in China under Climate Change and Their Physical Quantification Based on a Regional Climate Model and CMIP5 Model Simulations

The atmospheric water holding capacity will increase with temperature according to Clausius-Clapeyron scaling and affects precipitation. The rates of change in future precipitation extremes are quantified with changes in surface air temperature. Precipitation extremes in China are determined for the 21st century in six simulations using a regional climate model, RegCM4, and 17 global climate models that participated in CMIP5. First, we assess the performance of the CMIP5 models and RCM runs in their simulation of extreme precipitation for the current period (RF: 1982–2001). The CMIP5 models and RCM results can capture the spatial variations of precipitation extremes, as well as those based on observations: OBS and XPP. Precipitation extremes over four subregions in China are predicted to increase in the mid-future (MF: 2039–58) and far-future (FF: 2079–98) relative to those for the RF period based on both the CMIP5 ensemble mean and RCM ensemble mean. The secular trends in the extremes of the CMIP5 models are predicted to increase from 2008 to 2058, and the RCM results show higher interannual variability relative to that of the CMIP5 models. Then, we quantify the increasing rates of change in precipitation extremes in the MF and FF periods in the subregions of China with the changes in surface air temperature. Finally, based on the water vapor equation, changes in precipitation extremes in China for the MF and FF periods are found to correlate positively with changes in the atmospheric vertical wind multiplied by changes in surface specific humidity (significant at the p < 0.1 level).

ИЗМЕНЕНИЯ ПРИЗЕМНОЙ ТЕМПЕРАТУРЫ ВОЗДУХА НА ЮГЕ СИБИРИ И ИХ ВЗАИМОСВЯЗЬ С КРУПНОМАСШТАБНЫМИ ЦИРКУЛЯЦИОННЫМИ ПРОЦЕССАМИ В АТМОСФЕРЕ

The article analyzes changes in surface air temperature in the south of Siberia, in 8 regions of the Russian Federation. Based on the geographical and climatic approaches, the study area was divided into four zones. It is shown that interannual changes in air temperature both within the identified zones and between them are consistent, while changes in the series of average monthly air temperatures are not so unambiguous. The calculated values of the linear trends of long-term changes in the mean annual air temperature indicate that, despite its widespread significant increase, in the last decade, a slowdown in the temperature growth has been noted across the territory of southern Siberia. An increase in air temperature is observed in almost all months of the year, with the exception of the winter period, when, according to data from individual meteorological stations, a slight fall in temperature is noted. An assessment of the relationship between air temperature and circulation mechanisms, carried out using correlation analysis, indicates a significant influence of the Scandinavian teleconnection index practically throughout the year in zones related to areas of continental climate. In areas of a sharply continental climate, its influence decreases to some extent, especially in summer, although it remains the leading factor in some months. The ongoing climatic changes cannot but entail both positive and negative socio-economic effects. In this regard, the results of the research should be taken into account when developing mechanisms for adapting the economy to climate change at regional levels.

Modulation of vegetation restoration on outdoor thermal comfort over the Loess Plateau, China from 1982 to 2015

This study depicts changes in the warm season (May to September) Universal Thermal Climate Index (UTCI) quantifying outdoor thermal comfort over the Loess Plateau from 1982 to 2015 and examines its relationship with large-scale climate changes and local vegetation restoration under the Grain for Green Program (GGP) after 1999. The results show that the UTCI experienced an increasing trend of 0.074/a from 1982 to 1999 and subsequently experienced a weakly decreasing trend of −0.002/a from 1999 to 2015. This trend shift in the UTCI was predominantly determined by surface air temperature changes with slopes of 0.077 °C a−1 from 1982 to 1999 and −0.005 °C a−1 from 1999 to 2015. The hiatus in the regional temperature rise after 1999 was closely related to the large-scale climate warming hiatus. Meanwhile, both measurement data analysis and climate modeling with the Weather Research and Forecasting (WRF) model suggest that the trend shift was also accelerated by vegetation restoration after 1999 through the intensification of transpiration, which increased the latent heat flux and reduced sensible heat flux. In particular, at the stations with the greatest degree of vegetation restoration, the local forcing from vegetation restoration was likely greater than that from the large-scale climate warming hiatus. This study highlights the importance of substantial vegetation restoration on local and regional thermal comfort.

Оценка влияния учета аэрозолей на прогноз температуры по данным модели COSMO-Ru

Aerosol effects on the forecast of surface temperature, as well as temperature at the levels of 850 and 500 hPa over Europe and the European part of Russia are studied using various aerosol climatologies: Tanre, Tegen, and MACv2. The numerical experiments with the COSMO-Ru model are performed for the central months of the seasons (January, April, July, and October) in 2017. It is found that a change in the simulated surface air temperature over land can reach 1C when using Tegen and MACv2 data as compared to Tanre. At 850 and 500 hPa levels, the changes do not exceed 0.4C. At the same time, it is shown that a decrease in the root-mean-square error of 2-m air temperature forecast at individual stations reaches 0.5C when using Tegen and MACv2 data and 1C for clear-sky conditions in Moscow.

Future projections for terrestrial biomes indicate widespread warming and moisture reduction in forests up to 2100 in South America

Terrestrial biomes are the main reservoirs of biodiversity and CO2 on the planet. In South America, they play a crucial role in climate regulation and biodiversity conservation. Despite scientific advances and recent efforts, there is still no detailed analysis of trends in surface air temperature and precipitation changes until the end of the 21st century and magnitude of change for South America’s terrestrial biomes. In this study, we used the annual mean of temperature and annual cumulative precipitation variables provided by WorldClim (version 2.1) from an ensemble of five Global Circulation Models from the most recent simulations of the CMIP6 project. We used four-time intervals between 2020 and 2100, combined at two climatic trajectories (SSP2-4.5 and SSP5-8.5), to map climate change scenarios’ trend magnitude in South America. Also, we evaluate the exposure level of the nine terrestrial biomes according to their respective vegetal cover densities. Our results indicate that in the two possible futures evaluated (SSP2-4.5 & SSP5-8.5), the terrestrial biomes of South America would be exposed to climatic conditions that are not analogous to the current ones. The results indicate a persistent and long-term annual temperature trend increase, indistinctly for all terrestrial biomes and a significant moisture reduction in forest biomes. The consolidation of such climate scenarios can make potentially modify water and carbon cycling patterns and promoting biodiversity loss, mainly at forest biomes, with probably more severe effects under the pessimistic scenario.

Fast responses of Northern Hemisphere winter daily circulation to anthropogenic aerosols

Anthropogenic aerosols (AA) have significantly caused anomalous winter mean atmospheric circulation over the Northern Hemisphere, but the main daily patterns of winter large-scale circulation change are not well understood. Here a self-organizing map analysis is applied to identify the leading patterns in AA-induced winter daily geopotential height (Z) anomaly fields simulated by three atmospheric general circulation models, with a focus on fast adjustments. Two winter daily circulation response patterns with a synoptic time scale are found: one pattern shows concurring Z anomalies over North America and North Asia with the same sign and the Bering Sea seeing the opposite, resembling the Asia–Bering–North American teleconnection; while the other is the Arctic Oscillation-like pattern with similar Z anomalies over North Pacific and North Atlantic and the opposite over the Arctic region. The AA-induced anomalous precipitation over the tropics and anomalous synoptic eddy activities over the extratropical oceans concur to support and maintain these circulation anomaly patterns. The winter-mean climate responses to AA can be understood as a result of these daily anomaly patterns, especially over the higher latitudes. Specifically, the associated changes in surface air temperature (SAT) over the mid-high latitudes are caused by the AA-driven meridional movements of polar (cold and dry) airmass and midlatitude (warm and moist) airmass in the regions, mainly through the relevant surface downward longwave radiation. This study highlights the role of AA in altering daily weather patterns, which is not sufficiently captured by seasonal mean responses.

Unnatural trend of global land long‐term surface air temperature change

AbstractIn the context of global warming, determining to what extent natural variability and external forcing have an impact on climate change is crucial for formulating mitigation policies and adaptation plans. We quantifiably and effectively separate unnatural trends from the global land surface air temperature (SAT) changes during 1951–2015 by calculating the long‐term correlation exponent through detrended fluctuation analysis and applying mainly probability statistics methods. We provide effective discriminated evidence for whether the observed SAT change exceeds its natural internal variability. Furthermore, we search the range of SAT changes caused by unnatural trends, and identify their corresponding minimum contributions to warming relative trends in different regions. The unnatural warming of the mid‐ to high latitude inland areas of Eurasia and North America is basically high, and the warming responses to unnatural forcing are most intense in these areas. Compared to earlier detection, we find the minimum unnatural trend contributes more than 80% to the observed SAT change in North America, northern Greenland, eastern Africa, and the mid‐ to high latitudes of Eurasia. In addition, the temporal evolutions of unnatural trends in key areas are determined. In North Africa, Western Australia, the United States and Mexico, the unnatural impact became significant at the earliest. Meanwhile, the overall unnatural trend in North Africa is the most significant, followed by western Brazil, and grows most rapidly over time in the two key areas.

Emergent constraints on equilibrium climate sensitivity in CMIP5: do they hold for CMIP6?

Abstract. An important metric for temperature projections is the equilibrium climate sensitivity (ECS), which is defined as the global mean surface air temperature change caused by a doubling of the atmospheric CO2 concentration. The range for ECS assessed by the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report is between 1.5 and 4.5 K and has not decreased over the last decades. Among other methods, emergent constraints are potentially promising approaches to reduce the range of ECS by combining observations and output from Earth System Models (ESMs). In this study, we systematically analyze 11 published emergent constraints on ECS that have mostly been derived from models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) project. These emergent constraints are – except for one that is based on temperature variability – all directly or indirectly based on cloud processes, which are the major source of spread in ECS among current models. The focus of the study is on testing if these emergent constraints hold for ESMs participating in the new Phase 6 (CMIP6). Since none of the emergent constraints considered here have been derived using the CMIP6 ensemble, CMIP6 can be used for cross-checking of the emergent constraints on a new model ensemble. The application of the emergent constraints to CMIP6 data shows a decrease in skill and statistical significance of the emergent relationship for nearly all constraints, with this decrease being large in many cases. Consequently, the size of the constrained ECS ranges (66 % confidence intervals) widens by 51 % on average in CMIP6 compared to CMIP5. This is likely because of changes in the representation of cloud processes from CMIP5 to CMIP6, but may in some cases also be due to spurious statistical relationships or a too small number of models in the ensemble that the emergent constraint was originally derived from. The emergently- constrained best estimates of ECS also increased from CMIP5 to CMIP6 by 12 % on average. This can be at least partly explained by the increased number of high-ECS (above 4.5 K) models in CMIP6 without a corresponding change in the constraint predictors, suggesting the emergence of new feedback processes rather than changes in strength of those previously dominant. Our results support previous studies concluding that emergent constraints should be based on an independently verifiable physical mechanism, and that process-based emergent constraints on ECS should rather be thought of as constraints for the process or feedback they are actually targeting.

Changes in Annual Extremes of Daily Temperature and Precipitation in CMIP6 Models

AbstractThis study presents an analysis of daily temperature and precipitation extremes with return periods ranging from 2 to 50 years in phase 6 of the Coupled Model Intercomparison Project (CMIP6) multimodel ensemble of simulations. Judged by similarity with reanalyses, the new-generation models simulate the present-day temperature and precipitation extremes reasonably well. In line with previous CMIP simulations, the new simulations continue to project a large-scale picture of more frequent and more intense hot temperature extremes and precipitation extremes and vanishing cold extremes under continued global warming. Changes in temperature extremes outpace changes in global annual mean surface air temperature (GSAT) over most landmasses, while changes in precipitation extremes follow changes in GSAT globally at roughly the Clausius–Clapeyron rate of ~7% °C−1. Changes in temperature and precipitation extremes normalized with respect to GSAT do not depend strongly on the choice of forcing scenario or model climate sensitivity, and do not vary strongly over time, but with notable regional variations. Over the majority of land regions, the projected intensity increases and relative frequency increases tend to be larger for more extreme hot temperature and precipitation events than for weaker events. To obtain robust estimates of these changes at local scales, large initial-condition ensemble simulations are needed. Appropriate spatial pooling of data from neighboring grid cells within individual simulations can, to some extent, reduce the needed ensemble size.

Opposing Trends of Winter Cold Extremes over Eastern Eurasia and North America under Recent Arctic Warming

Under recent Arctic warming, boreal winters have witnessed severe cold surges over both Eurasia and North America, bringing about serious social and economic impacts. Here, we investigated the changes in daily surface air temperature (SAT) variability during the rapid Arctic warming period of 1988/89–2015/16, and found the daily SAT variance, mainly contributed by the sub-seasonal component, shows an increasing and decreasing trend over eastern Eurasia and North America, respectively. Increasing cold extremes (defined as days with daily SAT anomalies below 1.5 standard deviations) dominated the increase of the daily SAT variability over eastern Eurasia, while decreasing cold extremes dominated the decrease of the daily SAT variability over North America. The circulation regime of cold extremes over eastern Eurasia (North America) is characterized by an enhanced high-pressure ridge over the Urals (Alaska) and surface Siberian (Canadian) high. The data analyses and model simulations show the recent strengthening of the high-pressure ridge over the Urals was associated with warming of the Barents–Kara seas in the Arctic region, while the high-pressure ridge over Alaska was influenced by the offset effect of Arctic warming over the East Siberian–Chukchi seas and the Pacific decadal oscillation (PDO)–like sea surface temperature (SST) anomalies over the North Pacific. The transition of the PDO-like SST anomalies from a positive to negative phase cancelled the impact of Arctic warming, reduced the occurrence of extreme cold days, and possibly resulted in the decreasing trend of daily SAT variability in North America. The multi-ensemble simulations of climate models confirmed the regional Arctic warming as the driver of the increasing SAT variance over eastern Eurasia and North America and the overwhelming effect of SST forcing on the decreasing SAT variance over North America. Therefore, the regional response of winter cold extremes at midlatitudes to the Arctic warming could be different due to the distinct impact of decadal SST anomalies.

The Role of Samalas Mega Volcanic Eruption in European Summer Hydroclimate Change

In this study, the role of AD 1258 Samalas mega volcanic eruption in the summer hydroclimate change over Europe and the corresponding mechanisms are investigated through multi-member ensemble climate simulation experiments based on the Community Earth System Model (CESM). The results show that the CESM simulations are consistent with the reconstructed Palmer Drought Severity Index (PDSI) and the historical records of European climate. Europe experiences significant summer cooling in the first three years after the Samalas mega volcanic eruption, peaking at −3.61 °C, −4.02 °C, and −3.21 °C in year 1 over the whole Europe, Southern Europe, and Northern Europe, respectively. The summer surface air temperature (SAT, °C) changes over the European continent are mainly due to the direct weakening of shortwave solar radiation induced by volcanic aerosol. The summer precipitation over the European continent shows an obvious dipole distribution characteristic of north-south reverse phase. The precipitation increases up to 0.42 mm/d in year 1 over Southern Europe, while it decreases by −0.28 mm/d in year 1 over Northern Europe, respectively. Both simulations and reconstructions show that the centers with the strongest increase in precipitation have always been located in the Balkans and Apennine peninsulas along the Mediterranean coast over Southern Europe, and the centers with the strongest precipitation reduction are mainly located in the British Isles and Scandinavia over northwestern Europe. The negative response of North Atlantic Oscillation (NAO) with significant positive sea level pressure (SLP) anomaly in the north and negative SLP anomaly in the south is excited in summer. The low tropospheric wind anomaly caused by the negative phase of NAO in summer affects the water vapor transport to Europe, resulting in the distribution pattern of summer precipitation in Europe, which is drying in the north and wetting in the south. The knowledge gained from this study is crucial to better understand and predict the potential impacts of single mega volcanic eruption on the future summer hydroclimate change in Europe.

Evaluation of Ground Temperature Changes by the Operation of the Geothermal Heat Pump System and Climate Change in Korea

To evaluate long-term temperature changes caused by the operation of a geothermal heat pump (GHP) system, temperatures near borehole heat exchangers (BHEs) of the GHP system in Korea were measured. The temperature measurements showed increasing rates of 0.135 °C/year at a depth of 10 m and 0.118 °C/year at a depth of 50 m for approximately 10 years. Simulations for the analysis of climate change effects on measured temperature fluctuations showed that a rate of temperature increase was 0.010 °C/year at a depth of 50 m owing to changes in surface air temperatures (SATs). From two-dimensional heat transfer simulations, the discharged heat measuring 16.7 W/m in the cooling season and extracted heat measuring 12.4 W/m in the heating season could cause an annual mean temperature increase of 0.109 °C over approximately 10 years. Additionally, results of simulations for future prediction of ground temperatures assuming that the GHP system retains its level of operation showed that in 2050, temperature at a depth of 50 m will increase by approximately 3.00 °C from that in 2005. Thus, balancing the heat discharged into and extracted from the ground by considering climate change to minimize long-term changes in the ground temperature is necessary.

Future projection of greenhouse gas emissions due to permafrost degradation using a simple numerical scheme with a global land surface model

The Yedoma layer, a permafrost layer containing a massive amount of underground ice in the Arctic regions, is reported to be rapidly thawing. In this study, we develop the Permafrost Degradation and Greenhouse gasses Emission Model (PDGEM), which describes the thawing of the Arctic permafrost including the Yedoma layer due to climate change and the greenhouse gas (GHG) emissions. The PDGEM includes the processes by which high-concentration GHGs (CO2 and CH4) contained in the pores of the Yedoma layer are released directly by dynamic degradation, as well as the processes by which GHGs are released by the decomposition of organic matter in the Yedoma layer and other permafrost. Our model simulations show that the total GHG emissions from permafrost degradation in the RCP8.5 scenario was estimated to be 31-63 PgC for CO2 and 1261-2821 TgCH4 for CH4 (68th percentile of the perturbed model simulations, corresponding to a global average surface air temperature change of 0.05–0.11 °C), and 14-28 PgC for CO2 and 618-1341 TgCH4 for CH4 (0.03–0.07 °C) in the RCP2.6 scenario. GHG emissions resulting from the dynamic degradation of the Yedoma layer were estimated to be less than 1% of the total emissions from the permafrost in both scenarios, possibly because of the small area ratio of the Yedoma layer. An advantage of PDGEM is that geographical distributions of GHG emissions can be estimated by combining a state-of-the-art land surface model featuring detailed physical processes with a GHG release model using a simple scheme, enabling us to consider a broad range of uncertainty regarding model parameters. In regions with large GHG emissions due to permafrost thawing, it may be possible to help reduce GHG emissions by taking measures such as restraining land development.

Distinct response of Northern Hemisphere land monsoon precipitation to transient and stablized warming scenarios

To better understand the climate response under stabilized, overshoot, and transient global warming, four types of ensemble experiments on 1.5 °C/2 °C global warming scenarios (i.e., stabilized 1.5 °C, 1.5 °C overshoot, stabilized 2 °C, and transient 2 °C) are elaborately designed using the Nanjing University Information Science and Technology Earth System Model (NESM). Compared with the modern climate (1985–2014), the projected surface air temperature (SAT) change is characterized by a robust ‘Northern Hemisphere (NH)-warmer than-Southern Hemisphere (SH)’ and ‘land-warmer than-ocean’ patterns. The projected precipitation change exhibits ‘NH-wetter than-SH’ pattern in the tropics. Although the response of SAT and precipitation climatology show similar pattern between stabilized and overshoot scenarios, some significant differences are still found. The projected change in the Northern Hemisphere land monsoon precipitation (NHLMP) is 30% larger in the transient 2 °C experiment compared with that in the stabilized 2 °C experiment. The more vigorous NHLMP in the transient global warming scenario is mainly due to the enhanced land–sea thermal contrast and interhemispheric temperature difference. The enlarged land–sea thermal contrast increases the surface pressure gradient between the NH continents and its adjacent oceans, thus enhancing the NH monsoon circulation and moisture convergence. The enhanced interhemispheric temperature difference shifts the Hadley circulation and intertropical convergence zone northward, leading to the enhanced moisture convergence and the shifts of tropical rain band over the NH monsoon region. This result highlights that climate responses may depend on different warming trajectories and, which could facilitate the strategic planning of governments.

Greenland surface air temperature changes from 1981 to 2019 and implications for ice‐sheet melt and mass‐balance change

AbstractWe provide an updated analysis of instrumental Greenland monthly temperature data to 2019, focusing mainly on coastal stations but also analysing ice‐sheet records from Swiss Camp and Summit. Significant summer (winter) coastal warming of ~1.7 (4.4)°C occurred from 1991–2019, but since 2001 overall temperature trends are generally flat and insignificant due to a cooling pattern over the last 6–7 years. Inland and coastal stations show broadly similar temperature trends for summer. Greenland temperature changes are more strongly correlated with Greenland Blocking than with North Atlantic Oscillation changes. In quantifying the association between Greenland coastal temperatures and Greenland Ice Sheet (GrIS) mass‐balance changes, we show a stronger link of temperatures with total mass balance rather than surface mass balance. Based on Greenland coastal temperatures and modelled mass balance for the 1972–2018 period, each 1°C of summer warming corresponds to ~(91) 116 Gt·yr−1 of GrIS (surface) mass loss and a 26 Gt·yr−1 increase in solid ice discharge. Given an estimated 4.0–6.6°C of further Greenland summer warming according to the regional model MAR projections run under CMIP6 future climate projections (SSP5‐8.5 scenario), and assuming that ice‐dynamical losses and ice sheet topography stay similar to the recent past, linear extrapolation gives a corresponding GrIS global sea‐level rise (SLR) contribution of ~10.0–12.6 cm by 2100, compared with the 8–27 cm (mean 15 cm) “likely” model projection range reported by IPCC in 2019 (SPM.B1.2). However, our estimate represents a lower limit for future GrIS change since fixed dynamical mass losses and amplified melt arising from both melt‐albedo and melt‐elevation positive feedbacks are not taken into account here.

Seasonal temperature response over the Indochina Peninsula to a worst-case high-emission forcing: a study with the regionally coupled model ROM

Changes of surface air temperature (SAT) over the Indochina Peninsula (ICP) under the Representative Concentration Pathway (RCP) 8.5 scenario are projected for wet and dry seasons in the short-term (2020–2049) and long-term (2070–2099) future of the twenty-first century. A first analysis on projections of the SAT by the state-of-the-art regionally coupled atmosphere-ocean model ROM, including exchanges of momentum, heat, and water fluxes between the atmosphere (Regional Model) and ocean (Max Planck Institute Ocean Model) models, shows the following results: (i) In both seasons, the highest SAT occurs over the southern coastal area while the lowest over the northern mountains. The highest warming magnitudes are located in the northwestern part of the ICP. The regionally averaged SAT over the ICP increases by 2.61 °C in the wet season from short- to long-term future, which is slightly faster than that of 2.50 °C in the dry season. (ii) During the short-term future, largest SAT trends occur over the southeast and northwest ICP in wet and dry seasons, respectively. On regional average, the wet season is characterized by a significant warming rate of 0.22 °C decade−1, while it is non-significant with 0.11 °C decade−1 for the dry season. For the long-term future, the rapid warming is strengthened significantly over whole ICP, with trends of 0.51 °C decade−1 and 0.42 °C decade−1 in wet and dry seasons, respectively. (iii) In the long-term future, more conspicuous warming is noted, especially in the wet season, due to the increased downward longwave radiation. Higher CO2 concentrations enhancing the greenhouse effect can be attributed to the water vapor–greenhouse feedback, which, affecting atmospheric humidity and counter radiation, leads to the rising SAT.