Annual Temperature Trends Research Articles

Temperature and precipitation trend over 139 major Indian cities: An assessment over a century

The increasing temperature in an urban area has adversely affected the Earth’s environment, human health and has been a subject of prior considerable attention. Hence, for the sustainable development and adaptation of the urban population to climate change, it is essential to find the trend and magnitude of temperature and precipitation over Indian cities. An endeavor has been made in the present study to find the trend and magnitude of temperature and precipitation over 139 major Indian cities with respect to different Koppen climatic zones using Climatic Research Unit datasets of last 115 years (1901–2015). The annual and seasonal trend and magnitude of temperature and precipitation of these cities were assessed using non-parametrical modified Mann–Kendall and Sens’s slope test. The results indicate that the annual and seasonal temperature trend was significantly deceasing over the cities of north western region whereas an increasing trend in the south eastern cities of India. A significant relationship was observed between temperature and precipitation in the hot steppe (BSh), dry winter humid subtropical (Cwa) and tropical wet and dry (Aw) climatic zone. The distribution of precipitation trend is highly heterogeneous and uneven as compared to temperature. The eastern part of India shows decreasing precipitation trend in comparison with the western part.

Observed and Perceived Climate Change and Variability and Small Holder Farmers’ Vulnerability: The Case of Janamora District, Northwestern Ethiopia

In the context of observed climate change and variability and their impact on livelihoods; This study intended to assess farmers’ vulnerability to climate change and variability in Janamora district, northwestern Ethiopia. Primary data for the study was collected through questionnaire from 138 respondents selected through multi-stage sampling technique based on agro-ecology. Secondary data was collected from meteorological stations. Mann-Kendall and Chi-square tests were employed to test observed and perceived climate change and variability respectively. While LVI and LVI-IPCC methods were used to assess farmers’ vulnerability to climate change and variability using SPSS version 23. The results revealed significant increasing trend in annual average temperature in all stations except Debark and insignificant trend in annual rainfall as well as a higher rainfall variability. Similarly, 69.6 and 80.4% of the interviewed farmers were aware of an increase in temperature and a decrease in rainfall respectively. Moreover, χ 2 test showed that a significant variation (significant at P<0.05) in perception to temperature and rainfall between agro-ecology. The overall vulnerability result in the case of LVI was 0.425, 0.454 and 0.471 for Dega, Woyna Dega and Kolla agro-ecological zones respectively. Similar result was found using the LVI-IPCC approach which was 0.035, 0.041 and 0.049 for Dega, Woyna Dega and Kolla agro-ecological zones respectively. Both LVI and LVI-IPCC results revealed that Kolla was the most vulnerable and Dega was the least vulnerable to climate change and variability. The study suggested improving the literacy level and integrating rural development schemes to increase adaptive capacity. Similarly, further studies should be conducted in the future. Keywords: Perception, Vulnerability, Climate Change and Variability, Livelihood, Janamora DOI : 10.7176/JEES/9-8-04 Publication date : August 31 st 2019

Comparing precipitation and temperature trends between inland and coastal locations

Motivated by the Millennium Drought and the current drought over much of southern and eastern Australia, this detailed statistical study compares trends in annual wet season precipitation and temperature between a coastal site (Newcastle) and an inland site (Scone). Bootstrap permutation tests reveal Scone precipitation has decreased significantly over the past 40 years (p-value=0.070) whereas Newcastle has recorded little to no change (p-value=0.800). Mean maximum and minimum temperatures for Newcastle have increased over the past 40 years (p-values of 0.002 and 0.015, respectively) while the mean maximum temperature for Scone has increased (p-value = 0.058) and the mean minimum temperature has remained stable. This suggests mean temperatures during the wet season for both locations are increasing. Considering these trends along with those for precipitation, water resources in the Hunter region will be increasingly strained as a result of increased evaporation with either similar or less precipitation falling in the region. Wavelet analysis reveals that both sites have similar power spectra for precipitation and mean maximum temperature with a statistically significant signal in the two to seven year period, typically indicative of the El-Nino Southern Oscillation climate driver. The El-Nino Southern Oscillation also drives the Newcastle mean minimum temperature, whereas the Scone power spectra has no indication of a definitive driver for mean minimum temperature. 
 
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Testing lichenometric techniques in the production of a new growth-rate (curve) for the Breiðamerkurjökull foreland, Iceland, and the analysis of potential climatic drivers of glacier recession

ABSTRACTIndependent dating of closely-spaced moraines on the west Breiðamerkurjökull foreland is used to test the accuracy of the size frequency (SF) and largest lichen (5LL) lichenometric dating techniques. The 5LL technique derived the most accurate ages for three undated moraines within the dated sequence but growth rates and lag times produced by the two methods (5LL = 0.71 mm yr−1 and 11 years; SF = 0.64 mm yr−1 and 7 years) were not significantly different. We therefore reject previous conclusions that any one technique is demonstrably inferior to the other, at least for dating glacial landforms created over the last 130 years in SE Iceland. Comparisons of climate trends and recession rates indicate that air temperature anomalies, particularly those of the summer, are the strongest driver of glacier retreat. No clear relationship between NAO trends and glacier retreat were identified, although a positive and/or rising trend in NAO is associated with the slowing of ice retreat overall, and the marked readvances of the mid-1950s, mid-1970s and mid-1990s are all coincident with positive and/or rising NAO 5yr moving averages. Summer and annual temperature trends, not the NAO, clearly show that recent accelerated global warming is driving the marked recession of the period 1995–2015. Over the last 100 years temperature has been the major driver of glacier terminus oscillations at west Breiðamerkurjökull but it is clear that extreme decreases in winter precipitation (i.e. 1960–1973) have the potential to increase retreat rates significantly even during times of below average annual temperatures.

A new homogenized daily data set for temperature variability assessment in Italy

AbstractWe present a new data set of quality‐controlled and homogenized daily maximum (Tmax) and minimum (Tmin) temperature for Italy. The data set includes 144 Tmax and 139 Tmin long‐term series, covering the period 1961–2017. First, the paper provides a description of data sources and quality controls implemented for the detection of erroneous daily observations. Next, the temperature records used for this work are introduced. Following strict data continuity and completeness requirements, we identified more than 500 time series with at least 20 years of valid data (raw data set), which were spatially partitioned using a hierarchical clustering approach. For each cluster, the time series homogeneity was assessed using two different statistical automatic approaches: ACMANT and Climatol. The results of the homogenization process are illustrated only for the long‐term series subset. Both homogenization methods revealed the presence of non‐climatic discontinuities in most of the temperature series. Although Climatol detected a slightly lower number of breakpoints than ACMANT, the two methods are in good agreement with respect to the statistics which describe the number and timing of the breakpoints. Since no metadata are available, the plausibility of the homogenized time series was evaluated using different statistical measures: RMSE, Spearman correlation coefficient and trends estimation. Our results show that the homogenized data sets are more spatially coherent than the raw time series. In particular, the analysis of the annual temperature trends shows more realistic and reliable climatic patterns when the homogenized data sets are considered. For our data, the homogenization process only marginally changes the annual and seasonal warming trend values found for the area‐averaged anomaly raw series. The Tmax and Tmin homogenized data set will be regularly updated and is intended to be used for a variety of climate studies that require data at daily resolution, as the analysis of climate extremes.

Climate Variability and Farmers’ Perception in Southern Ethiopia

The study aims to analyze climate variability and farmers’ perception in Southern Ethiopia. Gridded annual temperature and precipitation data were obtained from the National Meteorological Agency (NMA) of Ethiopia for the period between 1983 and 2014. Using a multistage sampling technique, 403 farm households were surveyed to substantiate farmers’ perceptions about climate variability and change. The study applied a nonparametric Sen’s slope estimator and Mann–Kendall’s trend tests to detect the magnitude and statistical significance of climate variability and binary logit regression model to find factors influencing farm households’ perceptions about climate variability over three agroecological zones (AEZs). The trend analysis reveals that positive trends were observed in the annual maximum temperature, 0.02°C/year (p<0.01) in the lowland and 0.04°C/year (p<0.01) in the highland AEZs. The positive trend in annual minimum temperature was consistent in all AEZs and significant (p<0.01). An upward trend in the annual total rainfall (10 mm/year) (p<0.05) was recorded in the midland AEZ. Over 60% of farmers have perceived increasing temperature and decreasing rainfall in all AEZs. However, farmers’ perception about rainfall in the midland AEZ contradicts with meteorological analysis. Results from the binary logit model inform that farmers’ climate change perceptions are significantly influenced by their access to climate and market information, agroecology, education, agricultural input, and village market distance. Based on these results, it is recommended to enhance farm households’ capacity by providing timely weather and climate information along with institutional actions such as agricultural extension services.

Disequilibrium in Trait-Climate Relationships of Trees and Birds

Climate change is expected to drive changes in the structure of ecological assemblages, but these responses might show considerable time lags. If these lags are large, then the observed composition of assemblages will fall out of equilibrium with current climatic conditions. This disequilibrium has several expected signatures, including trends in the magnitude of climate relationships through time and stronger climate relationships across space than through time. Here, I describe spatial and temporal patterns of functional assemblage composition of birds and trees and ask whether there is evidence of disequilibrium between climate and functional assemblage structure. I used bird assemblage data from the Breeding Bird Survey (BBS) and tree data from the Forest Inventory and Analysis program (FIA), in both cases spanning the continental United States and covering the time period 1970-2016. To describe functional assemblage composition, I used the community weighted means of five functional traits for trees and six traits for birds, and fit linear models to explain the variation in composition through time and across space. For most traits, spatial relationships were much stronger than temporal relationships, consistent with lagged responses of assemblages to climate change. Several of the traits showed trends over the study period, in some cases associated with trends in mean annual temperature. Others showed dynamics in the spatial relationships between climate and trait values. For example, the mean clutch size of birds depended only weakly on temperature in the early study period, but the relationship became strongly negative by 2016. While precipitation was often an important predictor of spatial patterns of functional composition, it was typically weakly correlated with the temporal patterns. This likely reflects the fact that temperature experienced more consistent long-term trends over the study period, whereas large year-to-year fluctuations in precipitation prevent composition from ever coming into equilibrium with precipitation in a particular year. Overall, there was substantial evidence of disequilibrium between functional assemblage composition and climate.

Trend Analyses of Temperature and Rainfall and Their Response to Global CO2 Emission in Masha, Southern Ethiopia

Ethiopia is one of the most vulnerable countries to climate change and often signifies higher probabilities of droughts that have historically affected millions of farmers. The variability in rainfall patterns and drought have disrupted crop production and exacerbated food insecurity in many parts of Ethiopia. This study aimed to investigate seasonal and annual temperature and rainfall trends and their association to the global CO<sub>2</sub> emission. Temperature and rainfall data obtained from the Masha meteorological station and CO<sub>2</sub> from EDGAR 4.3.2 dataset recorded for 36 years. The Linear regression model was used to analyse seasonal temperature and rainfall trends. Pearson’s correlation coefficient employed to measure the relationship between temperature and rainfall and global CO<sub>2</sub> emission. The results showed that there were significant warming trends of seasonal and annual mean temperatures while summer season and annual rainfall significantly declined. The prediction results showed that the summer and annual mean temperatures would be significantly increased while the rainfall decreased for the next 35 years. The cumulative global CO<sub>2</sub> and annual mean temperature and rainfall were correlated significantly at P = 0.0004 and 0.006 for temperature and rainfall, respectively. The results demonstrated clearly that the increasing of temperature and the decreasing of rainfall had a direct relationship with the global CO<sub>2</sub> emissions and suggested that there should be a sound soil and water management, short season seed supply and pipe irrigation practices to reduce the future crop damage in the area.

Spatiotemporal Variability in Land Surface Temperature Over the Mountainous Region Affected by the 2008 Wenchuan Earthquake From 2000 to 2017

AbstractThe mountainous region affected by the 2008 Wenchuan earthquake was frequently analyzed to assess its vegetation recovery. However, the dynamic of surface thermal environment was rarely investigated but directly influenced local geophysical and biophysical processes. Under this background, this research aimed to analyze the trend of surface temperature based on Moderate Resolution Imaging Spectroradiometer daily land surface temperature product from 2000 to 2017 and understand its change mechanism. An annual temperature cycle model was applied to obtain the daytime and nighttime annual cycle parameters (ACPs), including mean annual surface temperature (MAST), yearly amplitude of surface temperature, and phase shift. The trend analysis with the Mann‐Kendall test illustrated the strong inverse relationship between the two ACPs (MAST and yearly amplitude of surface temperature) and elevation, and the nighttime terms showed a stronger connection than those of the daytime. The areas with significant decreases in vegetation coverage induced by the earthquake exhibited an obvious upward trend in daytime MAST and annual maximum temperature, while the vegetation improved areas presented a cooling effect. Comparatively, the nighttime ACPs was little sensitive to vegetation change and the change magnitude was relatively small. For the high mountain area, with the shrinkage of snow cover duration, the global warming effect resulted in a warming trend by increasing the annual minimum temperature at both the daytime and nighttime. Overall, this study provided insights to the impact of the earthquake to mountain thermal environment and its different responses to changes in vegetation cover and climatic environment.

Analysis of long-term seasonal and annual temperature trends in North Bengal, India

In the recent past, scientific modeling of climatic elements, in particular, temperature data has attained considerable importance as it affects many aspects of the environment and also indicates a clear sign of climate change. The temperature warming is mainly associated with the increasing concentration of greenhouse gases triggered by the land use and land cover changes. In the last century, exploitation of forest resource, population influx, and expansion of agricultural land has changed the natural landscape of North Bengal to a great extent. Thus the present study intends to find out long-term changes in maximum and minimum temperature for six northern districts of the state of West Bengal, popularly known as North Bengal. The non-parametric Mann–Kendall test and Theil-Sen’s slope estimator reveals the presence of warming trends in both maximum and minimum temperature. Annual temperature is rising 0.006 °C per year and 0.007 °C per year at most of the districts for the maximum and minimum temperature respectively. However, the seasonal analysis of trend exposes that post-monsoon and winter temperature rise are predominantly contributing to the upward annual trend. The highest increasing trend in maximum and minimum temperature is observed at Malda (0.013 °C per year) in the post-monsoon and winter season respectively. Except the post-monsoon season, the minimum temperature is rising rapidly than maximum temperature across the region. Additionally, Sequential Mann–Kendall test exhibits the periodic fluctuation of trends, which are more prominent in pre-monsoon and monsoon season.

Climate change drives glacier retreat in Bhaga basin located in Himachal Pradesh, India

This paper reports changes in different glaciers of Bhaga basin located in western Himalaya, from 1979 to 2017. Glacier boundaries were delineated through semi-automated approach using Landsat satellite imagery. The variation of glacier extent in different elevation zones, snout retreat and decadal changes are observed. Results show that the total area of glaciers was 238 in 1979, which reduced to 230.8 by 2017 (retreat rate 12 ). Glaciers at low elevation and smaller in size are retreating faster. Analysis of Asian Precipitation-Highly Resolved Observational Data Integration Towards Evaluation data shows decreasing trend of annual precipitation (–2.724, 1951–2015) and increasing trend of mean annual temperature (0.021). The statistical analysis using Mann-Kendall and Sen’s slope tests, applied at different confidence interval demonstrates that climate change corresponds to deglaciation, and topography controls glacier recession in the basin.

Dynamics of the temperature regime of the North Atlantic coastal zone as an indicator of changes in the system of thermohaline circulation

The purpose of the article is to analyze dynamics of the temperature regime of the surface layer of the atmosphere in the coastal zone of the North Atlantic as an indicator of changes in the thermohaline circulation system. In carrying out the research, comparative-geographical and historical statistical methods of the analysis of meteorological series were used. For research, 20 control points of the eastern part of the United States and Western Europe, which are located along the flow course of the Gulf Stream, are selected. In the selected points, by means of the linear trend method, the regularities of the dynamics of the mean annual, average maximum and average minimum temperatures of the atmospheric surface layer for the period from 1973 to 2013 have been established. The results of the study showed that, contrary to the hypothesis of fall in temperature in Europe, an increase in average annual and average maximum temperatures is observed in all control points of the region - the range means the linear trend is from 0.9 to 4.4 o F and from 0.3 to 3.8 o F respectively. In most US control points, the average annual temperature rises from 0.1 to 3 o F and the average maximum temperature rises from 0.2 to 2.1 oF. For four points of the United States the decrease in the values of the linear trend of average annual temperatures is from -0.4 to -1.2 o F; for three points - a decrease in average maximum temperatures is from -1.3 to -1.9 o F. At 9 control points in the USA and 8 control points in Europe, the average values of the minimum temperatures in the research period increased - in the USA, from 0.1 to 3.1 o F; in Europe from 0.3 to 4.6 o F. The opposite dynamics in the regions is observed for the values of the temperature amplitude. In most control points in Europe, the difference between the average maximum and the average minimum annual temperatures ranged from 0.4 to 6.6 o F; in most US destinations, on the contrary, a decrease in the amplitude value from -1.6 to -3 oF is observed. The analysis of the temperature dynamics of the surface layer of the atmosphere indicates the prevailing warming processes in the coastalzone of the North Atlantic, more intense for control points in Western Europe. The obtained data give grounds for refuting hypotheses of the presence of critical deviations in the thermohaline circulation system of the Atlantic Ocean, which could lead to a cooling in the Northern Hemisphere. The change in the amplitude values is a manifestation of increasing instability of the climate, which is likely to remain in the future with a general increase in the mean annual temperature in the region.

Climate Trends of Temperature, Precipitation and River Discharge in the Abbay River Basin in Ethiopia

Projecting future changes of streamflow in the Abby River Basin (ARB) is important for planning and proper management of the basin system. The current study conducted in five stations of the Abbay river basin, and investigated the annual temperature, precipitation, and river discharge variability using the Innovative trend analysis method, Mann-Kendall, and Sen’s slope test estimator. The result showed a slightly increasing trend of annual precipitation in Assoa (Z = 0.71), Bahir Dar (Z = 0.13), and Gonder (Z = 0.26) stations, while a significant increasing trend was observed in Nedgo (Z = 2.45) and Motta (Z = 1.06) stations. Interestingly, the trend of annual temperature in Assosa (Z = 5.88), Bahir Dar (Z = 3.87), Gonder (Z = 4.38), Nedgo (Z = 4.77), and Motta (Z = 2.85) was abruptly increased. The average mean temperature has increased by 0.2°C in the past 36 years (1980 to 2016). The extreme high temperature was observed in the semi-dry zone of northern Ethiopia. During the study period, a significant declining trend of the river discharge was recorded, and the river discharge was sharply decreased from 1992 onwards. The results of the current study showed annual variability of river discharge, precipitation, and temperature of the study area of the basin that could be used as a basis for future studies.

Observed Trends of Climate and River Discharge in Mongolia’s Selenga Sub-Basin of the Lake Baikal Basin

Mongolia’s Selenga sub-basin of the Lake Baikal basin is spatially extensive, with pronounced environmental gradients driven primarily by precipitation and air temperature on broad scales. Therefore, it is an ideal region to examine the dynamics of the climate and the hydrological system. This study investigated the annual precipitation, air temperature, and river discharge variability at five selected stations of the sub-basin by using Mann-Kendall (MK), Innovative trend analysis method (ITAM), and Sen’s slope estimator test. The result showed that the trend of annual precipitation was slightly increasing in Ulaanbaatar (Z = 0.71), Erdenet (Z = 0.13), and Tsetserleg (Z = 0.26) stations. Whereas Murun (Z = 2.45) and Sukhbaatar (Z = 1.06) stations showed a significant increasing trend. And also, the trend of annual air temperature in Ulaanbaatar (Z = 5.88), Erdenet (Z = 3.87), Tsetserleg (Z = 4.38), Murun (Z = 4.77), and Sukhbaatar (Z = 2.85) was sharply increased. The average air temperature has significantly increased by 1.4 °C in the past 38 years. This is very high in the semi-arid zone of central Asia. The river discharge showed a significantly decreasing trend during the study period years. It has been apparent since 1995. The findings of this paper could help researchers to understand the annual variability of precipitation, air temperature, and river discharge over the study region and, therefore, become a foundation for further studies.

Assessment of atmospheric conditions over the Hong Thai Binh river watershed by means of dynamically downscaled ERA-20C reanalysis data

Abstract Long-term, high spatial and temporal resolution of atmospheric data is crucial for the purpose of reducing the effects of hydro-meteorological risks on human society in an economically and environmentally sustainable manner. However, such information usually is limited in transboundary regions due to different governmental policies, and to conflicts in the sharing of data. In this study, high spatial and temporal resolution atmospheric data were reconstructed by means of the Weather Research and Forecasting Model-WRF with input provided from the global atmospheric reanalysis of the 20th century (ERA-20C) over the Hong-Thai Binh River watershed (H-TBRW). The WRF model was implemented over the physical boundaries of the study region based on ERA-20C reanalysis data and was configured based on existing ground observation data in Vietnam's territories, and the global Aphrodite precipitation data. With the validated WRF model for H-TBRW, the reconstructed atmospheric data were first reconstructed for 1950–2010, and then were evaluated by time series and spatial analysis methods. The results of this study suggest no significant trend in the annual accumulated precipitation depth, while there were upward trends in annual temperature at both the point and watershed scale. Furthermore, the results confirm that topographic conditions have significant effects on the climatic system such as on precipitation and temperature.

Impact of climatic change on water resources in Huia river basin, China

Research on the impact of climate change on water resources has attracted the attention of academician and policy makers. This paper tends to analyze the impact of changes in air temperature and rainfall factors on the amount of water resources in the Huai River Basin from 1980 to 2014. Air temperature and rainfall data were collected from six meteorological stations. Hydrological and water resources evaluation data were collected from the Bengbu Hydrological Station in the Huai River Basin. Research findings revealed an increasing trend of average annual air temperature, with the highest increase of 0.293oC recorded at Bengbu in Anhui Province. The western part of the study area has shown a rising rainfall while the eastern part (the middle reaches of the Huai River) witnessed a declining rainfall. The rainfall in the Huai River Basin was significantly influenced by the natural fluctuations as the average rainfall in the study area was in a vaguely declining trend. This resulted in gradual decrease in the quantity of the Basin’s water resources due to decreasing rainfall and rising air temperature. Regression and sensitivity analyses were employed to develop a mathematical model between water resources quantity and changes in air temperature and rainfall. Based on regression analysis findings, changes in rainfall have a much bigger impact on its water resources quantity than changes in its air temperature.

Recognition of Local Authority for Better Management of Drinking Water at the Langat River Basin, Malaysia

Integrated Langat River Basin Management lacks appropriate leadership of appropriate agency due to the conflict among jurisdictions since Langat River drains through three different constituency. Meanwhile, pollution of the river and frequent shutdown incidents of water treatment plants in the basin are evident due to both point and non-point sources of pollutions. Moreover, the statistically significant trend of annual rainfall (2005-2016) and temperature (2005-2016) in the basin clearly indicates the impact of climate change because of uncertain rainfall and temperature patterns. Flood incidents (2004-2016) within the basin in comparison with the rainfall and temperature also indicate short duration heavy rainfall at local level to enhance the pollution of the river. Contrary, the review of literature and informal interviews with the public, private and civil sectors highlight the attitude problem of the stakeholders along lack of leadership of LUAS in managing the river and drinking water in the basin. Therefore, the ‘proactive’ leadership of Local Authority under the Local Government Act 1976 could be successful to coordinate with stakeholders through multi stakeholders’ platform and several stages of quality control and quality assurance to manage water resources. The study suggests a new Langat Basin Management Authority under the Local Authority leadership as well as a Two-Layer water filtration technology in basin management. Henceforth, implementing the recommendations will facilitate Malaysia to achieve SDGs 2030 and National Transformation 2050 within the stipulated timeframe.

Contiguous US summer maximum temperature and heat stress trends in CRU and NOAA Climate Division data plus comparisons to reanalyses

Warming is a major climate change concern, but the impact of high maximum temperatures depends upon the air’s moisture content. Trends in maximum summertime temperature, moisture, and heat index are tracked over three time periods: 1900–2011, 1950–2011, and 1979–2011; these trends differ notably from annual temperature trends. Trends are emphasized from two CRU datasets (CRUTS3.25 and CRUTS4.01) and two reanalyses (ERA-20C and 20CRv2). Maximum temperature trends tend towards warming that is stronger over the Great Lakes, the interior western and the northeastern contiguous United States. A warming hole in the Midwest generally decreases in size and magnitude when heat stress trends are calculated because the region has increasing moisture. CRU and nearly all reanalyses find cooling in the northern high plains that is not found in NOAA Climate Division trends. These NOAA trends are captured better by CRUTS401. Moistening in the northeast amplifies the heat stress there. Elsewhere the moisture trends are less clear. Drying over northern Texas (after 1996) in CRUTS401 translates into decreasing heat stress there (less so in CRUTS325). Though other reanalyses are not intended for long-term trends, MERRA-2 and ERA-Interim match observed trends better than other reanalyses.

Skill of the two 20th century reanalyses in representing Antarctic near‐surface air temperature

The performance of the 20th century reanalysis (20CR) and of the pilot reanalysis of the 20th century (ERA‐20C) for Antarctic near‐surface air temperature is investigated based on quality‐controlled monthly temperature measurements with a time coverage of at least 15 years from 42 automatic and manual weather stations, and temperature reconstructions. On the inter‐annual timescale, ERA‐20C and 20CR agree well with the temperature observations since 1957/1958, but there are systematic biases relative to absolute values with cold bias at East Antarctic coastal stations, and warm bias over the inland stations. An abrupt upwards shift in Antarctic annual and seasonal (except summer) mean temperature averaged over the East Antarctic ice sheet and the Antarctic ice sheet occurs around 1950 in 20CR and around 1979 in ERA‐20C, which is probably related to the increasing counts of assimilated observations. Moreover, the significantly negative trends of seasonal and annual mean temperature in 20CR since the late 1970s are found to be largely spurious, which most likely results from the poor representation of variability in sea surface temperature (SST) around Antarctica in the 20CR's boundary forcing. These results imply and urge that caution must be taken when applying the two global reanalyses for evaluating long‐term climate changes at high southern latitudes.

Climate shifts within major agricultural seasons for +1.5 and +2.0 °C worlds: HAPPI projections and AgMIP modeling scenarios

This study compares climate changes in major agricultural regions and current agricultural seasons associated with global warming of +1.5 or +2.0 °C above pre-industrial conditions. It describes the generation of climate scenarios for agricultural modeling applications conducted as part of the Agricultural Model Intercomparison and Improvement Project (AgMIP) Coordinated Global and Regional Assessments. Climate scenarios from the Half a degree Additional warming, Projections, Prognosis and Impacts project (HAPPI) are largely consistent with transient scenarios extracted from RCP4.5 simulations of the Coupled Model Intercomparison Project phase 5 (CMIP5). Focusing on food and agricultural systems and top-producing breadbaskets in particular, we distinguish maize, rice, wheat, and soy season changes from global annual mean climate changes. Many agricultural regions warm at a rate that is faster than the global mean surface temperature (including oceans) but slower than the mean land surface temperature, leading to regional warming that exceeds 0.5 °C between the +1.5 and +2.0 °C Worlds. Agricultural growing seasons warm at a pace slightly behind the annual temperature trends in most regions, while precipitation increases slightly ahead of the annual rate. Rice cultivation regions show reduced warming as they are concentrated where monsoon rainfall is projected to intensify, although projections are influenced by Asian aerosol loading in climate mitigation scenarios. Compared to CMIP5, HAPPI slightly underestimates the CO2 concentration that corresponds to the +1.5 °C World but overestimates the CO2 concentration for the +2.0 °C World, which means that HAPPI scenarios may also lead to an overestimate in the beneficial effects of CO2 on crops in the +2.0 °C World. HAPPI enables detailed analysis of the shifting distribution of extreme growing season temperatures and precipitation, highlighting widespread increases in extreme heat seasons and heightened skewness toward hot seasons in the tropics. Shifts in the probability of extreme drought seasons generally tracked median precipitation changes; however, some regions skewed toward drought conditions even where median precipitation changes were small. Together, these findings highlight unique seasonal and agricultural region changes in the +1.5 °C and +2.0 °C worlds for adaptation planning in these climate stabilization targets.