Past versions of global surface temperature (ST) datasets have been shown to have underestimated the recent warming trend over 1998–2012. This study uses a newly updated global land surface air ...temperature and a land and marine surface temperature dataset, referred to as China global land surface air temperature (C-LSAT) and China merged surface temperature (CMST), to estimate trends in the global mean ST (combining land surface air temperature and sea surface temperature anomalies) with the data uncertainties being taken into account. Comparing with existing datasets, the statistical significance of the global mean ST warming trend during the past century (1900–2017) remains unchanged, while the recent warming trend during the “hiatus” period (1998–012) increases obviously, which is statistically significant at 95% level when fitting uncertainty is considered as in previous studies (including IPCC AR5) and is significant at 90% level when both fitting and data uncertainties are considered. Our analysis shows that the global mean ST warming trends in this short period become closer among the newly developed global observational data (CMST), remotely sensed/Buoy network infilled datasets, and reanalysis data. Based on the new datasets, the warming trends of global mean land SAT as derived from C-LSAT 2.0 for the period of 1979–2019, 1951–2019, 1900–2019 and 1850–2019 were estimated to be 0.296, 0.219, 0.119 and 0.081 °C/decade, respectively. The warming trends of global mean ST as derived from CMST for the periods of 1998–2019, 1979–2019, 1951–2019 and 1900–2019 were estimated to be 0.195, 0.173, 0.145 and 0.091 °C/decade, respectively.
This paper presents an analysis of the relationship between land surface temperatures (LST) and screen‐level air temperatures (T2m) using in situ observations from 19 Atmospheric Radiation ...Measurement (ARM) deployments located in a range of geographical regimes. The diurnal cycle is resolved using 1 min observations: a particular focus of the study is on the relationship between daily extremes of LST (LSTmax, LSTmin) and T2m (Tmax, Tmin). Temperature differences are analyzed with respect to cloud, wind speed, and snow cover. Under cloud‐free, low wind speed conditions, daytime LST is often several degrees Celsius (°C) higher than T2m at low‐to‐middle latitudes and at high latitudes during the summer months. In contrast, LST and T2m are often close (e.g., within 2°C) under cloudy and/or moderate‐to‐high wind speed conditions or when solar insolation is low or absent. LSTmin and Tmin are generally well correlated (r > 0.8, often r > 0.9), while seasonal correlations between LSTmax and Tmax are weaker (r > 0.6, often r > 0.8). At high latitudes, LST and T2m are well coupled in spring/autumn/winter; the relationship between LST and T2m tends to weaken with decreasing latitude. The timing of daily extremes is also investigated and it is found that LSTmin and Tmin typically occur close to sunrise, with Tmin occurring slightly after LSTmin. LSTmax occurs close to solar noon, with Tmax typically occurring 1–3 hours later. This study will inform temperature data users on differences between LST and T2m and aid development of methods to estimate T2m using satellite LSTs.
Key Points
The land skin‐air temperature relationship is characterized using in situ data from the Atmospheric Radiation Measurement program
Example diurnal temperature evolutions are presented, and the timing and magnitude of daily extreme temperatures are analyzed
Cloud, wind, and snow cover are found to affect the land skin‐air temperature relationship
Pakistan is one of the most vulnerable countries of the world to temperature extremes due to its predominant arid climate and geographic location in the fast temperature rising zone. Spatial ...distribution of the trends in annual and seasonal temperatures and temperature extremes over Pakistan has been assessed in this study. The gauge-based gridded daily temperature data of Berkeley Earth Surface Temperature (BEST) having a spatial resolution of 1° × 1° was used for the assessment of trends over the period 1960–2013 using modified Mann-Kendall test (MMK), which can discriminate the multi-decadal oscillatory variations from secular trends. The results show an increase in the annual average of daily maximum and minimum temperatures in 92 and 99% area of Pakistan respectively at 95% level of confidence. The annual temperature is increasing faster in southern high-temperature region compared to other parts of the country. The minimum temperature is rising faster (0.17–0.37 °C/decade) compared to maximum temperature (0.17–0.29 °C/decade) and therefore declination of diurnal temperature range (DTR) (− 0.15 to − 0.08 °C/decade) in some regions. The annual numbers of both hot and cold days are increasing in whole Pakistan except in the northern sub-Himalayan region. Heat waves are on the rise, especially in the hot Sindh plains and the Southern coastal region, while the cold waves are becoming lesser in the northern cold region. Obtained results contradict with the findings of previous studies on temperature trends, which indicate the need for reassessment of climatic trends in Pakistan using the MMK test to understand the anthropogenic impacts of climate change.
Variability and change in near‐surface air temperature at 17 Antarctic stations is examined using data from the SCAR READER database. We consider the relationships between temperature, and ...atmospheric circulation, sea ice concentration and forcing by the tropical oceans. All 17 stations have their largest inter‐annual temperature variability during the winter and the annual mean temperature anomalies are dominated by winter temperatures. The large inter‐annual temperature variability on the western Antarctic Peninsula has decreased over the instrumental period as sea ice has declined. Variability in the phase of the SAM exerts the greatest control of temperatures, although tropical Pacific forcing has also played a large part, along with local atmospheric circulation variability at some locations. The relationship of positive (negative) SAM and high (low) Peninsula and low (high) East Antarctic temperatures was not present before the mid‐1970s. Thirteen of the 17 stations have experienced a positive trend in their annual mean temperature over the full length of their record, with the largest being at Vernadsky (formerly Faraday) (0.46° ± 0.15°C·dec−1) on the western side of the Antarctic Peninsula. The deepening of the Amundsen Sea low as a result of the more positive SAM and changes in the IPO and PDO have contributed to the warming of the Peninsula. Beyond the Antarctic Peninsula there has been little significant change in temperature. The two plateau stations had a small cooling from the late 1970s to the late 1990s consistent with the SAM becoming positive, but have subsequently warmed. During spring there has been an Antarctic‐wide warming, with all but one station having experienced an increase in temperature, although the only trends that were significant were at Vostok, Scott base, Vernadsky and Amundsen‐Scott. In this season, much of the Peninsula/West Antarctic warming can be attributed to tropical Pacific forcing through the IPO/PDO.
Over recent decades, temperatures across the Antarctic continent have exhibited a complex picture of change with a marked warming of the Antarctic Peninsula but with little overall change elsewhere. The ozone hole has contributed significantly to the warming of the Peninsula, although tropical Pacific climate variability has also played a part. The largest seasonal Antarctic‐wide change has been a warming during the spring, with much of this attributable to tropical variability.
Future changes in the mean, maximum and minimum temperature in the Iberian Peninsula were investigated using bias-corrected EURO-CORDEX climate projections. The results show that the future ...temperatures are projected to substantially increase in all the Iberian Peninsula, particularly towards the end of the century at the south-central region. Mean and maximum temperatures are projected to increase around 2 °C (4 °C) for the 2046–2065 (2081–2100) period, with much higher frequencies of days above 20 (mean temperature) and 30 °C (maximum temperature). However, much higher increases are projected in the south of Spain, Cantabrian and Pyrinees mountain ranges, while lower ones are projected for the Atlantic coastal areas. In the south-central part of the Iberian Peninsula, hot days (mean temperature > 30 °C) are projected to increase 20–35 days/year (40–80 days/year) for the period 2046–2065 (2081–2100), while very hot days (maximum temperature > 40 °C) are projected to increase 10–25 days/year (10–50 days/year) for the period 2046–2065 (2081–2100). These results show a clear tendency, associated with a high confidence, in a significant increase of the surface temperatures and in the frequency of high temperature episodes in the southern part of the Iberian Peninsula, which can have severe impacts on the population, environment and economy. The currently hottest areas located in south-central Iberian Peninsula are also the ones with the highest projected temperature increases, which will significantly exacerbate the temperature stress in these areas.
Understanding the long-term change of extreme temperature events is important to the detection and attribution of climate change. It is unclear, however, how much effect urbanization has had on ...trends of the extreme temperature indices series constructed based on the commonly used datasets on a subcontinental scale. Applying a homogenized daily temperature dataset of the national reference climate stations and basic meteorological stations, and a rural station network previously developed, urbanization effects on trends of extreme temperature indices in mainland China for the time period 1961–2008 are evaluated. It is found that 1) the country-averaged annual- and seasonal-mean extreme temperature indices series generally experience statistically significant trends; 2) annual-mean urbanization effects in the country as a whole are statistically significant for daily minimum temperature (Tmin), maximum temperature (Tmax), and mean temperature of Tmin and Tmax (Tavg), reaching 0.070°, 0.023°, and 0.047°C(10 yr)−1, respectively, with the largest values for annual-mean Tmin occurring in north China; 3) annual- and seasonal-mean urbanization effects for the declining diurnal temperature range (DTR) are highly significant, and the largest seasonal-mean DTR decline because of urbanization occurs in winter and spring; 4) annual-mean urbanization effects for the lowest Tmin, summer days, tropical nights, and frost days series are significant, but an insignificant urbanization effect is detected for icing days series; 5) urbanization has led to a highly significant decline of annual cold nights at a rate of −1.485 days (10 yr)−1and a highly significant increase of annual warm nights at a rate of 2.264 days (10 yr)−1. Although urbanization effects are also significant for cold days and warm days, they are relatively smaller, and 6) the smallest absolute values of annual-mean urbanization effects for most of the indices series are found to dominantly appear during 1966–76, a well-known deurbanization period resulting from the Cultural Revolution.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This study investigates the long‐term variability of surface air temperature (SAT) over the Arabian Peninsula (AP), using data from the Climate Research Unit (TS 3.22) for the 1960–2010 period. The ...long‐term climatology suggests that the warmest AP mean temperatures occur during summer, with the highest temperatures over the northern AP (NAP), due to the monsoon–desert mechanism. During winter, the NAP exhibits low SATs under the influence of western disturbances originating from the Mediterranean. The southwestern AP exhibits the lowest temperatures because of its proximity to the Arabian Sea cold waters, and also because of the orographic effects. The inter‐annual variability of the SAT is stronger during winters. A linear trend analysis reveals a significant increase in the SAT anomaly (0.10 °C/decade) across the AP, consistently with the global temperature anomalies. Besides the local convective heating, summer SAT variability is associated with the weakening of the Asian jet stream and a Rossby wave train from the Indian Ocean. This variability is also influenced by the anomalous low pressure over the North Atlantic and the Sahara, a high‐pressure system over Siberia and the northwest Pacific. Both in spring and autumn, sea surface temperature (SST) variations over the Indo‐western Pacific are highly influenced the AP SATs, whereas winter SATs are modulated by the subtropical jet stream and the Middle East jet stream. In all seasons, the AP SAT is strongly influenced by the SST variations over the tropical oceans. The temperature variability is closely associated with the El Niño–Southern Oscillation (ENSO), North Atlantic Oscillation (NAO) and Arctic Oscillation (AO). The warm phase of ENSO (i.e., El Niño) is one possible reason behind the inter‐annual increase in SAT over the southern AP. The negative phases of NAO and AO also play a role in increasing AP SAT.
Seasonal and annual mean surface air temperature (°C, shaded) and standard deviation (contours) over the Arabian Peninsula for the period 1960–2010.
Over the past few decades, a growing body of epidemiological studies found the effects of temperature on cardiovascular disease, including the risk for acute myocardial infarction (AMI). Our study ...aimed to investigate whether there is an association between extremely temperature and acute myocardial infarction hospital admission in Beijng, China. We obtained 81029 AMI cases and daily temperature data from January 1, 2013 to December 31, 2016. We employed a time series design and modeled distributed lag nonlinear model (DLNM) to analyze effects of temperature on daily AMI cases. Compared with the 10th percentile temperature measured by daily mean temperature (Tmean), daily minimum temperature (Tmin) and daily minimum apparent temperature (ATmin), the cumulative relative risks (CRR) at 1st percentile of Tmean, Tmin and ATmin for AMI hospitalization were 1.15(95% CI: 1.02, 1.30), 1.24(95% CI: 1.11, 1.38) and 1.41(95% CI: 1.18, 1.68), respectively. Moderate low temperature (10th vs 25th) also had adverse impact on AMI events. The susceptive groups were males and people 65 years and older. No associations were found between high temperature and AMI risk. The main limitation of the study is temperature exposure was not individualized. These findings on cold-associated AMI hospitalization helps characterize the public health burden of cold and target interventions to reduce temperature induced AMI occurrence.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A global land–ocean temperature record has been created
by combining the Berkeley Earth monthly land temperature field with
spatially kriged version of the HadSST3 dataset. This combined product ...spans
the period from 1850 to present and covers the majority of the Earth's
surface: approximately 57 % in 1850, 75 % in 1880, 95 % in 1960, and
99.9 % by 2015. It includes average temperatures in 1∘×1∘ lat–long grid cells for each month when available. It provides
a global mean temperature record quite similar to records from Hadley's
HadCRUT4, NASA's GISTEMP, NOAA's GlobalTemp, and Cowtan and Way and
provides a spatially complete and homogeneous temperature field. Two
versions of the record are provided, treating areas with sea ice cover as
either air temperature over sea ice or sea surface temperature under sea
ice, the former being preferred for most applications. The choice of how to
assess the temperature of areas with sea ice coverage has a notable impact
on global anomalies over past decades due to rapid warming of air
temperatures in the Arctic. Accounting for rapid warming of Arctic air
suggests ∼ 0.1 ∘C additional global-average
temperature rise since the 19th century than temperature series that do
not capture the changes in the Arctic. Updated versions of this dataset will
be presented each month at the Berkeley Earth website
(http://berkeleyearth.org/data/, last access: November 2020), and a convenience copy of the version
discussed in this paper has been archived and is freely available at
https://doi.org/10.5281/zenodo.3634713 (Rohde and Hausfather,
2020).
Historical temperature variability over China during the twentieth century and projected changes under three emission scenarios for the twenty-first century are evaluated on the basis of a multimodel ...ensemble of 20 GCMs from phase 5 of the Coupled Model Intercomparison Project (CMIP5) and two observational datasets. Changes relative to phase 3 of the Coupled Model Intercomparison Project (CMIP3) are assessed, and the performance of individual GCMs is also quantified. Compared with observations, GCMs have substantial cold biases over the Tibetan Plateau, especially in the cold season. The timing and location of these biases also correspond to the greatest disagreement among the individual models, indicating GCMs’ limitations in reproducing climatic features in this complex terrain. The CMIP5 multimodel ensemble shows better agreement with observations than CMIP3 in terms of the temperature biases. Both CMIP3 and CMIP5 capture the climatic warming over the twentieth century. However, the magnitude of the annual mean temperature trends is underestimated. There is also limited agreement in the spatial and seasonal patterns of temperature trends over China. Based on six statistical measures, four individual models—the Max Planck Institute Earth System Model, low resolution (MPI-ESM-LR), Second Generation Canadian Earth System Model (CanESM2), Model for Interdisciplinary Research on Climate, Earth System Model (MIROC-ESM), and Community Climate System Model, version 4 (CCSM4)—best represent surface air temperature variability over China. The future temperature projections indicate that the representative concentration pathway (RCP) 8.5 and RCP 4.5 scenarios exhibit a gradual increase in annual temperature during the twenty-first century at a rate of 0.60° and 0.27°C (10 yr)−1, respectively. As the lowest-emission mitigation scenario, RCP 2.6 projects the lowest rate of temperature increase 0.10°C (10 yr)−1. By the end of the twenty-first century, temperature is projected to increase by 1.7°–5.7°C, with larger warming over northern China and the Tibetan Plateau.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK