Changes In Surface Air Temperature Research Articles

On the transition of temperature regime of the White Sea Region to a new phase state

Changes in near surface air temperature (SAT) and vorticity of the wind speed field of the White Sea and the territory of the Murmansk and Arkhangelsk regions and the Republic of Karelia are investigated. We analyzed the monthly average NCEP/ NCAR reanalysis data for the period 1950–2020. The average surface air temperature growth estimated using a linear trend was +0.240C/10 years. Against the background of this linear growth, significant interdecadal changes in surface air temperature are observed. The following periods are highlighted: the strengthening of the continentality of the climate (1950–1976), a more maritime climate (1977–1998), and the rapid growth of surface air temperature (1999–2020). The transition from a period of increasing continentality of the climate to a period of a more maritime climate is associated with an increase in the influence of the North Atlantic on the region under study. A hypothesis has been put forward that the period of rapid growth of surface air temperature is caused by the transition of the climatic system of the western part of the Russian Arctic into a new phase state. The observed warming in the Arctic has caused a reduction in sea ice, which has led to an increase in solar energy absorption by the surface of the Barents and White Seas.

Impacts of future urbanization on urban microclimate and thermal comfort over the Mumbai metropolitan region, India

This study examines the microclimatic impacts of future urbanization over the Mumbai Metropolitan Region (MMR) in India using a dynamic downscaling approach. Initially, two numerical experiments (curr_exp and fut_exp) were carried out by integrating 2018 and 2050 land-use/land-cover patterns under the same meteorological conditions. Afterwards, the spatial and temporal changes in surface air temperature, wind speed, and thermal discomfort were assessed by comparing the simulated results between curr_exp and fut_exp. To remediate the observed adverse microclimatic impacts of future urbanization, a mitigation strategy was designed and implemented in the third experiment (miti_exp). Simulation results show that the average maximum (minimum) surface air temperature of the region would increase by 1.41 °C (1.27 °C) due to future urbanization. However, if we adopt the mitigation strategy, this growth can be restricted to 0.69 °C (0.92 °C). In the context of thermal discomfort, an additional 20% of the total area can undergo hyperthermal treatment by 2050. This study reveals that although the implemented mitigation strategy can restrict the increasing temperature, it is ineffectual in minimizing the thermal discomfort level. The results of this study will be helpful in designing area-specific climate action plans through which goals of sustainable urban development can be accomplished.

Recent weakening linkage between Arctic oscillation and Aleutian low during boreal winter and its impact on surface temperature over Eastern Eurasia

AbstractWe investigated interdecadal relationship changes between the Arctic oscillation (AO) and Aleutian low (AL) for the period 1980–2021 along with the linkage on surface air temperature (SAT) over Eastern Eurasia during the boreal winter (December–January–February). The AO–AL relationship has weakened since the mid‐1990s. To explore a possible explanation, we compared atmospheric fields for two contrasting periods, one when the AO–AL relationship is the strongest (1986–2006) and one when it is the weakest (2000–2020). In both periods, atmospheric circulation over the Arctic region for the two AO–AL in‐phase relationships (i.e., either +AO/+AL or –AO/−AL) evolves with negative AO‐like patterns, contributing to a weakening AO–AL relationship in concurrent with a cool SAT in Eastern Eurasia. We found that the correlation between AL and SAT over Eastern Eurasia decreases, while the AO and SAT correlation remains unchanged. This implies that low‐frequency atmospheric circulation changes such as those of the AO and AL should be considered when studying SAT changes in Eastern Eurasia.

ВЗАИМОСВЯЗЬ ПЛОЩАДИ СНЕЖНОГО ПОКРОВА В СЕВЕРНОМ ПОЛУШАРИИ ПО СПУТНИКОВЫМ ДАННЫМ С ПРИПОВЕРХНОСТНОЙ ТЕМПЕРАТУРОЙ

The relationship between intraannual and interannual variations in the snow cover extent in the Northern Hemisphere, including Eurasia and North America and changes in surface air temperature was quantitatively estimated using satellite and reanalysis data for the period of 1979-2020. The estimates of the parameters of the snow cover extent sensitivity to temperature changes for the last four decades were compared with the estimates for the recent years (since 2005). The results of the correlation and cross-wavelet analysis indicate a general significant coherence and negative correlation between surface air temperature and the snow cover extent both for the entire Northern Hemisphere and separately for Eurasia and North America not only in the annual cycle but also in interannual variability for most months. Also, there is a positive correlation between the snow cover extent and surface air temperature in interannual variability, in particular, during the snow cover formation in the autumn months. It was found that the negative correlation between the snow cover extent and surface air temperature in Eurasia and North America for the recent years is higher than for the last four decades for most months except for the summer ones. The results indicate a weak coherence of interannual variations in the snow cover extent in Eurasia and North America, which is associated with the corresponding low coherence of interannual variations in surface air temperature for Eurasia and North America as a whole.

Trends in carbon sink along the Belt and Road in the future under high emission scenario

Over the past three decades, the drawdown of atmospheric CO2 in vegetation and soil has fueled net ecosystem production (NEP). Here, a global land-surface model (CABLE) is used to estimate the trend in NEP and its response to atmospheric CO2, climate change, biological nitrogen (N) fixation, and N deposition under future conditions from 2031 to 2100 in the Belt and Road region. The trend of NEP simulated by CABLE decreases from 0.015 Pg carbon (C) yr−2 under present conditions (1936–2005) to −0.023 Pg C yr−2 under future conditions. In contrast, the trend in NEP of the CMIP6 ensemble changes from 0.014 Pg C yr−2 under present conditions to −0.009 Pg C yr−2 under future conditions. This suggests that the trend in the C sink for the Belt and Road region will likely decline in the future. The significant difference in the NEP trend between present and future conditions is mainly caused by the difference in the impact of climate change on NEP. Considering the responses of soil respiration (RH) or net primary production (NPP) to surface air temperature, the trend in surface air temperature changes from0.01°C yr−1 under present conditions to 0.05°C yr−1 under future conditions. CABLE simulates a greater response of RH to surface temperature than that of NPP under future conditions, which causes a decreasing trend in NEP. In addition, the greater decreasing trend in NEP under future conditions indicates that the C–climate–N interaction at the regional scale should be considered. It is important to estimate the direction and magnitude of C sinks under the C neutrality target.摘要目前, 在区域尺度, NEP趋势变化的强度和影响机制还存在很大的不确定性. 针对这一问题, 我们选取了一带一路覆盖的区域为研究对象, 基于全球陆面模式 (CABLE)和第六次国际耦合模式比较计划 (CMIP6), 评估了历史和未来NEP趋势的变化, 分析了影响的机制. 从过去到未来, CABLE结果表明NEP的趋势从 0.015 Pg C yr−2 减少到 –0.023 Pg C yr−2; CMIP6结果为从0.014 Pg C yr−2转变为–0.009 Pg C yr−2. 气候变化是引起这一变化的主因. 我们的研究结果强调了碳-气候-氮相互作用的重要性, 这对碳中和目标下碳汇潜力的准确估算尤为重要.

Hysteresis of the Glacial Atlantic Meridional Overturning Circulation Controlled by Thermal Feedbacks

AbstractThe multiple equilibrium behavior of the Atlantic meridional overturning circulation (AMOC) is related to the mode transition of the AMOC, which played an important role in abrupt glacial climate changes. However, the difference between modern and glacial climates is not well understood. Here, we examined the structure of the multiple equilibria of the AMOC under the modern and glacial climates through hysteresis experiments using an earth system model of intermediate complexity. The glacial AMOC exhibited a shallower AMOC mode but not the off mode, and a narrower range of multiple equilibria than the modern AMOC. This glacial hysteresis behavior occurred associated with a shift of deep water formation due to changes in surface air temperature and sea ice, whereas that of the modern AMOC is attributed to the basin‐scale salinity feedback. These features were commonly found in two glacial simulations with different strengths of the AMOC at the Last Glacial Maximum.

Quasi‐biennial oscillation‐related surface air temperature change over the western North Pacific in late winter

AbstractThe impact of the quasi‐biennial oscillation (QBO) on the surface air temperature (SAT) in the Northern Hemisphere extratropics is investigated. It is found that the QBO, defined as 70‐hPa zonal wind in the deep tropics, is negatively correlated with the SAT over the western North Pacific in February and March. Cold temperature anomaly appears during the QBO westerly phase. Such relationship is likely mediated by the subtropical jet. During the QBO westerly phase, a horseshoe‐shaped zonal wind anomaly forms in the upper troposphere and lower stratosphere and is connected to the equatorward shift of the Asia‐Pacific jet. This equatorward jet shift is accompanied by a cyclonic circulation anomaly in the subtropical North Pacific and an anticyclonic circulation anomaly over northern Eurasia in the troposphere. The resultant temperature advection brings cold air to East Asia and the western North Pacific. This regional downward coupling in February and March, which is not sensitive to El Niño‐Southern Oscillation, has become statistically significant in recent decades.

Panama’s Current Climate Replicability in a Non-Hydrostatic Regional Climate Model Nested in an Atmospheric General Circulation Model

To simulate the current climate, a 20-year integration of a non-hydrostatic regional climate model (NHRCM) with grid spacing of 5 and 2 km (NHRCM05 and NHRCM02, respectively) was nested within the AGCM. The three models did a similarly good job of simulating surface air temperature, and the spatial horizontal resolution did not affect these statistics. NHRCM02 did a good job of reproducing seasonal variations in surface air temperature. NHRCM05 overestimated annual mean precipitation in the western part of Panama and eastern part of the Pacific Ocean. NHRCM05 is responsible for this overestimation because it is not seen in MRI-AGCM. NHRCM02 simulated annual mean precipitation better than NHRCM05, probably due to a convection-permitting model without a convection scheme, such as the Kain and Fritsch scheme. Therefore, the finer horizontal resolution of NHRCM02 did a better job of replicating the current climatological mean geographical distributions and seasonal changes of surface air temperature and precipitation.

On the dependency of GCM-based regional surface climate change projections on model biases, resolution and climate sensitivity

We investigate the dependency of projected regional changes in surface air temperature (SAT) and precipitation on the model biases, resolution and global temperature sensitivity in two global climate model (GCM) ensembles. End of twenty-first century changes under high end scenarios normalized in units of per degree of global warming (PDGW) are examined for CMIP5 (RCP8.5) and CMIP6 (SSP5-8.5) ensembles of comparable size over 26 sub-continental scale regions, for December–January–February (DJF) and June–July–August (JJA). A brief analysis is also carried out for the scenario SSP3-7.0, which shows results essentially in line with the SSP5-8.5 ones. We find that the average regional change patterns are very similar between the CMIP5 and CMIP6 ensembles, both for SAT and precipitation, with spatial correlations exceeding 0.84. Also similar are the regional bias patterns over most regions analyzed, suggesting that these two generations of models still share some common systematic errors. A statistically significant relationship between projected regional changes and biases is found in 27% of regional cases for both SAT and precipitation; between regional changes and model resolution in 2% of cases for SAT and 12% of cases for precipitation; and between regional changes and global temperature sensitivity in 19% of cases for SAT and 14% of cases for precipitation. Therefore, we assess that the GCM resolution does not appear to be a significant factor in affecting the sub-continental scale projected changes, at least for the resolution range in the CMIP5 and CMIP6 models, while global temperature sensitivity and especially model biases play a more important role. These dependencies are not always consistent between the CMIP5 and CMIP6 ensembles. Overall, in our assessment the CMIP6 ensemble does not appear to provide substantially different, and presumably improved, regional surface climate change information compared to CMIP5 despite the use of more comprehensive models and somewhat higher resolution.

Last glacial temperature reconstructions using coupled isotopic analyses of fossil snails and stalagmites from archaeological caves in Okinawa, Japan

We applied a new geoarchaeological method with two carbonate archives, which are fossil snails from Sakitari Cave and stalagmites from Gyokusen Cave, on Okinawa Island, Japan, to reconstruct surface air temperature changes over the northwestern Pacific since the last glacial period. Oxygen isotope ratios (δ18O) of modern and fossil freshwater snail shells were determined to infer seasonal temperature variations. The observational and analytical data confirm that δ18O values of fluid inclusion waters in the stalagmite can be regarded as those of spring waters at the sites where snails lived. Our results indicate that the annual mean, summer, and winter air temperatures were lower by 6–7 °C at ca. 23 thousand years ago (ka) and 4–5 °C at ca. 16–13 ka than those of the present day. Our reconstruction implies that surface air cooling was possibly two times greater than that of seawater around the Ryukyu Islands during the Last Glacial Maximum, which potentially enhanced the development of the East Asian summer monsoon during the last deglaciation. Considering the potential uncertainties in the temperature estimations, the climatic interpretations of this study are not necessarily definitive due to the limited number of samples. Nevertheless, our new geoarchaeological approach using coupled δ18O determinations of fossil snails and stalagmite fluid inclusion waters will be useful for reconstructing snapshots of seasonally resolved time series of air temperatures during the Quaternary.

Spatial patterns of multi–centennial surface air temperature trends in Antarctica over 1–1000 CE: Insights from ice core records and modeling

The spatial pattern of Antarctic surface air temperature variability on multi–decadal to multi–centennial time scales is poorly known because of the short instrumental records, the relatively small number of high–resolution paleoclimate observations, and biases in climate models. Here, changes in surface air temperature over Antarctica are reconstructed over the past two millennia using data assimilation constrained by different ice core water isotope records in order to identify robust signals. The comparison between previous statistically based temperature reconstructions and simulations covering the full Common Era driven by natural and anthropogenic forcings shows major discrepancies occurring in the period 1–1000 CE over East Antarctica, with the reconstructions displaying a warming over 1–500 CE that is not reproduced by the simulations. This suggests that the trends in the first millennium deduced from the statistically based reconstructions are unlikely to be entirely forced by external forcings. Our reconstructions show the high sensitivity of the 500-year temperature trend in Antarctica and its spatial distribution to selection of the records for the reconstructions, especially during 1–500 CE. A robust cooling over Antarctica during 501–1000 CE has been obtained in three data assimilation–based reconstructions with a larger magnitude in the WAIS than elsewhere over Antarctica, in agreement with previous estimates with the larger changes than simulated in climate models. The reconstructions for atmospheric circulation indicate that the pattern of temperature changes over 501–1000 CE is related to the positive trend of Southern Annular Mode and a deepening of Amundsen Sea Low. This confirms the role of internal variability in the temperature trends on multi–centennial scales.

Sinuosity of Atmospheric Circulation over Southeastern China and Its Relationship to Surface Air Temperature and High Temperature Extremes

Linking sinuosity, a fairly recently developed metric, with high temperature extremes (HTEs) can be both useful and insightful to better understand the physical mechanisms behind HTEs. However, it is not clear whether there exists a relationship between the sinuosity changes and HTE changes in present and future climate conditions over southeastern China. In this paper, the anomalous characteristics of the atmospheric circulation are quantified by sinuosity. Three sinuosity metrics are used in this study: individual sinuosity (SIN), aggregate sinuosity (ASIN), and comprehensive sinuosity (CSIN). Furthermore, we examine the relationship between sinuosity changes and HTE changes in present and future climate conditions. ASIN is strongly correlated with surface air temperature (SAT). We find that the influence of individual sinuosity (SIN) at different latitudes on the SAT of southeastern China is different. The SIN of low (middle) latitude isohypses has significant positive (negative) correlations with the SAT of southeastern China. The SIN of high-latitude isohypses is rather limited and can therefore be ignored. The projected relationship between the sinuosity changes and HTE changes in the late 21st century suggests similar results. The change in SAT is related to the changes in climate variables over southeastern China in the future, and these changes increase with the increase in Z500 or V850 and the decrease in U500. Moreover, the frequencies of large (small) comprehensive sinuosity (CSIN) values at low (mid) latitudes will increase. At the end of the 21st century, Z500 isohypses at different latitudes will have an obvious poleward shift. Our results indicate that measuring the aggregate waviness of the midtropospheric flow (via sinuosity) can provide insight regarding HTEs, and the climate model output can be used to examine the future likelihood of increased HTE.

Presentation and Evaluation of the IPSL‐CM6A‐LR Ensemble of Extended Historical Simulations

AbstractThe Institut Pierre‐Simon Laplace Climate Modeling Center has produced an ensemble of extended historical simulations using the IPSL‐CM6A‐LR climate model. This ensemble (referred to as IPSL‐EHS) is composed of 32 members over the 1850–2059 period that share the same external forcings but differ in their initial conditions. In this study, we assess the simulated decadal to multidecadal climate variability in the IPSL‐EHS. In particular, we examine the global temperature evolution and recent warming trends, and their consistency with ocean heat content and sea ice cover. The model exhibits a large low‐frequency internal climate variability. In particular, a quasi‐bicentennial mode of internal climate variability is present in the model and is associated with the Atlantic Meridional Overturning Circulation. Such variability modulates the global mean surface air temperature changes over the historical period by about 0.1K. This modulation is found to be linked to the phase present in the initial condition state of each member. This variability appears to decrease during the 1850–2018 period in response to external forcings. The analysis of the ocean heat content reveals furthermore an overestimation of the ocean stratification, which likely leads to an overestimation of the recent warming rate on average.

Increasing Difference in Interannual Summertime Surface Air Temperature Between Interior East Antarctica and the Antarctic Peninsula Under Future Climate Scenarios

Plain Language SummaryMelting of the Antarctic ice sheet and shelf in the future will be influenced by interannual changes in the surface air temperature (SAT) in Antarctica. The SAT changes in Antarctica are related to variations in the Southern Hemisphere Annular Mode (SAM) during the austral summer. The SAM is a dominant pattern of atmospheric variability in the Southern Hemisphere and influences the Antarctic SAT with opposite changes between the northern Antarctic Peninsula (AP) and Eastern Antarctica (EA). To project future changes in the Antarctic SAT, we analyzed historical and future simulations from the Climate Model Intercomparison Project 5 models. We found that the degree of opposite interannual SAT changes between EA and the AP increases in the future due to intensified magnitude of the SAM‐related circulation anomalies, and summers of warmer SAT in the northern AP and cooler SAT in EA increase by 4% in the future compared to the historical period. This finding has major consequences for glacier melting in the northern AP in the future because more days of extremely high SAT in the northern AP may occur in the future.

Performance of the CRA-40/Land, CMFD, and ERA-Interim Datasets in Reflecting Changes in Surface Air Temperature over the Tibetan Plateau

Performance of the CRA-40/Land, CMFD, and ERA-Interim Datasets in Reflecting Changes in Surface Air Temperature over the Tibetan Plateau

Reconciling Human and Natural Drivers of the Tripole Pattern of Multidecadal Summer Temperature Variations Over Eurasia

AbstractThe recent summer surface air temperature (SAT) changes over densely populated Eurasia exhibit a non‐uniform pattern with amplified warming over Europe and East Asia (EA) but weak warming over Central Asia (CA), forming a wave train‐like structure. However, the key factors that determine this non‐uniform warming pattern remain unclear. By analyzing observations and model simulations, here, we show that more than half of the SAT multidecadal variations from 1950 to 2014 over Europe‐west Asia and EA may have resulted from external forcing, rather than from internal variability in the Atlantic as previously thought. In contrast, the recent SAT over CA is influenced mainly by internal variations in the Atlantic and Pacific oceans. Large ensemble model simulations suggest that the forced SAT multidecadal variations over Eurasia are mainly caused by changes in greenhouse gases and aerosols. Our findings provide strong evidence for major impacts of external forcing on multidecadal climate variations over Eurasia.

Reducing Planetary Health Risks Through Short-Lived Climate Forcer Mitigation.

Global air pollution and climate change are major threats to planetary health. These threats are strongly linked through the short‐lived climate forcers (SLCFs); ozone (O3), aerosols, and methane (CH4). Understanding the impacts of ambitious SLCF mitigation in different source emission sectors on planetary health indicators can help prioritize international air pollution control strategies. A global Earth system model is applied to quantify the impacts of idealized 50% sustained reductions in year 2005 emissions in the eight largest global anthropogenic source sectors on the SLCFs and three indicators of planetary health: global mean surface air temperature change (∆GSAT), avoided PM2.5‐related premature mortalities and gross primary productivity (GPP). The model represents fully coupled atmospheric chemistry, aerosols, land ecosystems and climate, and includes dynamic CH4. Avoided global warming is modest, with largest impacts from 50% cuts in domestic (−0.085 K), agriculture (−0.034 K), and waste/landfill (−0.033 K). The 50% cuts in energy, domestic, and agriculture sector emissions offer the largest opportunities to mitigate global PM2.5‐related health risk at around 5%–7% each. Such small global impacts underline the challenges ahead in achieving the World Health Organization aspirational goal of a 2/3 reduction in the number of deaths from air pollution by 2030. Uncertainty due to natural climate variability in PM2.5 is an important underplayed dimension in global health risk assessment that can vastly exceed uncertainty due to the concentration‐response functions at the large regional scale. Globally, cuts to agriculture and domestic sector emissions are the most attractive targets to achieve climate and health co‐benefits through SLCF mitigation.

Future Changes in Early Spring Wind Speed and Surface Warming Acceleration in Snow‐Covered Areas

AbstractWe use a convection‐permitting regional climate model to investigate the effect of reduced snow cover on near‐surface wind speeds over complex Japanese terrain under a global warming scenario. At synoptic scales, global warming weakens the winter monsoon, which in turn weakens near‐surface winds around Japan. Reductions in snow cover, which are driven by global warming, drive localized acceleration of rising surface temperatures and prevent the formation of a stable atmospheric boundary layer. Collapse of the stable layer drives an increase in near‐surface wind speed and air temperature. This effect is stronger at low elevations and in basins, but does not occur at high elevations where there is no stable layer under current climate conditions, despite increased ground warming because of reduced snow cover under global warming conditions. A strong, stable, near‐surface atmospheric layer under current climate conditions can therefore influence future changes in wind speed and surface air temperature in snow‐covered areas.

Multi-model ensemble mean of global climate models fails to reproduce early twentieth century Arctic warming

The Arctic climate system is very sensitive to external perturbations, which results in more rapid surface air temperature (SAT) changes in the Arctic compared to lower latitudes. This study aims at assessing the performance of global climate models from the phases 5 and 6 of the Coupled Model Intercomparison Project (CMIP5 and CMIP6) in reproducing the periods of Arctic warming and cooling known from the observations. Two experiments are considered for 9 CMIP5 models, and one experiment is used for the 108 ensemble members from 32 CMIP6 models. The ensemble mean of unforced Arctic amplification variability in the CMIP5 pre-industrial control experiment suggests a crucial role of external forcings in the present Arctic amplification. The ensemble mean of the same models in the historical experiment shows a century-long upward trend and clearly reproduces the present-day Arctic amplification. However, there is no consistent response of increasing Arctic amplification in the early twentieth century warming period during the 1920s–1940s in the CMIP5 models. This indicates the 1920s–1940s Arctic warming was unlikely to happen due to external forcings. Using the large CMIP6 ensemble in the historical experiment we show that the multi-model ensemble mean in the new generation of high-resolution CMIP6 models does not reproduce that warming either, thus posing questions how well the models capture internal climate variability and distinguish it from natural and anthropogenic forcings. This issue ultimately affects the reliability of future Arctic climate projections.

Estimates of Direct Radiative Forcing Impact on Surface Air Temperature Changes in the Modern Period

Estimates of Direct Radiative Forcing Impact on Surface Air Temperature Changes in the Modern Period