The 2022 mega heatwave in South Asia in the observed and projected future climate

The heatwave in 2022 in South Asia disrupted the lives of millions of people and posed challenges to human health, energy, water, and food security. However, mega heatwaves’ causes, impacts, and occurrence (like in 2022) remain largely unrecognized. Here, we analyzed the 2022 heatwave, its mechanisms, and future likelihood using observational datasets and climate model simulations. In the last few years, the frequency and duration of heatwaves have significantly increased in South Asia. South Asia faced five continuous heatwave spells that lasted about 35 d during late February and April 2022, affecting a large part of the region. The year 2022 heatwave was unprecedented that caused a deficit in soil moisture and crop yield. Moreover, our results show that the excessive radiative heating of arid and semi-arid regions resulted in a high geopotential height and low pressure in South Asia during the 2022 mega heatwave. The climate model simulations show that such mega heatwaves are projected to become more frequent under the warmer world, and their time of emergence could be as early as the 2030s under the highest emission scenario. Earlier occurrences of mega heatwaves in the future will pose considerable adaptation challenges for food and water security in the region.


Introduction
Heatwaves and other climate extremes have received great attention in recent decades in South Asia due to their frequent occurrence and considerable impacts on agriculture, public health, and energy demands (Murari et al 2015, Mishra et al 2017, Hess et al 2018, Mukherjee and Mishra 2018, Nanditha et al 2020, Kumar and Singh 2021, Kumar et al 2022).The frequency and duration of heatwaves have increased over South Asia during the observed climate (Perkins et al 2012, Rohini et al 2016, Mishra et al 2017, Sharma and Mujumdar 2017), which caused mortality, crop failure, power outages, and forest fire (Murari et al 2015, Im et al 2017, Mazdiyasni et al 2017, Mishra et al 2017, Jain et al 2021).For instance, the 2015 heatwave caused more than 1500 deaths [EMDAT: www.emdat.be;(Mishra et al 2017)] and also affected the water-energy-food nexus in the region (Mishra et al 2016).Changes in the heatwave characteristics (intensity, frequency, and duration) are directly linked with anthropogenic warming (Stott et al 2004, Dileepkumar et al 2021).Anthropogenic warming caused a rise of more than 1 • C in global mean temperature (GMT) with reference to the pre-industrial period , which resulted in an increase in heatwave frequency and severity across the globe (Stott et al 2004, Perkins et al 2012, Rohini et al 2016, Panda et al 2017, Seneviratne et al 2021).
The world has witnessed new records of temperature rise in the last few years (Bador et al 2017, Salinger et al 2019, Heeter et al 2023).With the warmest years in the instrumental record, heatwaves have become more frequent and severe recently.The unprecedented heatwaves have been analyzed in previous studies to understand the occurrence, severity, and associated mechanisms during the observed and future warming climate (Bador et al 2017, Salinger et al 2019, Dong et al 2023, Heeter et al 2023).For instance, Heeter et al (2023) showed that the 2 week long heatwave in 2021 over the Pacific Northwest of North America was unprecedented in the last millennium.Moreover, the risk of unprecedented heatwaves (like 2021) over the Pacific Northwest of North America will be 50% by 2050 (Dong et al 2023, Heeter et al 2023), primarily due to warming caused by anthropogenic emissions.Bador et al (2017) showed a significant amplification of mega heatwaves over France under the observed and future warming climate.Similar to worldwide unprecedented heatwaves, South Asia has also experienced anomalously high-temperature days in the year 2022, which resulted in an acute shortage of electricity and long-hours power outages in the region (Times of India 2022b; Varadhan 2022).The abnormal temperature rise in 2022 led to a devastating impact on the ecosystem, agriculture, and health sector (Basu 2022, DeAndreis 2022, Pandey 2022) and caused a loss of 90 lives and a 10%-35% reduction in crop yields in India and Pakistan (World Weather Attribution 2022a).Overall, the year 2022 heatwave posed a devastating impact on the densely populated South Asian region.Therefore, understanding the severity of the mega heatwaves (like the year 2022) under the warming climate is crucial to develop effective adaptation strategies in the region.Moreover, understanding the impacts of future mega heatwaves on crop yield and future water availability has become crucial due to the rising risk of heatwaves (Mishra et al 2021(Mishra et al , 2022)).
Here, we provide an assessment of the 2022 and future mega heatwaves using the reanalysis data from the European Centre for Medium-Range Weather Forecasts Reanalysis version 5 [ERA5; (Hersbach and Dee 2016)] and future climate projections from Coupled Model Intercomparison Project Phase 6 (CMIP6) (Eyring et al 1937).We investigate the characteristics, severity, and mechanism of the recently occurred mega heatwave of 2022, along with the time of emergence (ToE) of mega heatwaves in the future.We estimate the changes in annual heat accumulation (growing degree days; GDDs) in the future warming climate, which severely impact food production, water availability, and human health across the world (Overpeck 2013, Griffin and Anchukaitis 2014, Kukal and Irmak 2018, Mishra et al 2020).

Data and methods
We obtained daily maximum temperature (T max ), minimum temperature (T min ), sea level pressure (SLP), geopotential height (850 hPa), and wind speed (u and v component at 850 hPa) from European Centre for Medium-Range Weather Forecasts Reanalysis version 5 [ERA5; (Hersbach and Dee 2016)] at 0.25 • spatial resolution to examine the characteristics, severity and mechanism of the 2022 heatwave in South Asia.The ERA5 reanalysis performs better than other new-era reanalysis products (Mahto and Mishra 2019) and captures the spatial and temporal variability of temperature and precipitation over South Asia.Moreover, ERA5 reanalysis has been widely used for hydroclimatic and heatwave assessment across the globe (Mahto and Mishra 2019, Aadhar and Mishra 2020, Li 2020).Additionally, we used the satellite-based soil moisture and normalized difference vegetation index (NDVI) for the period 1982-2022 to analyze the impact of the 2022 heatwave over South Asia.The gridded satellite soil moisture was obtained from the European Space Agency Climate Change Initiative (ESA-CCI) at 0.25 • spatial resolution.We obtained the monthly NDVI data at 0.05 We used maximum temperature for the historical  and future (2015-2100) periods for four shared socioeconomic pathways (SSPs, SSP1-2.6,SSP2-4.5, SSP3-7.0, and SSP5-8.5)from 21 general circulation models (GCMs) that participated in the Coupled Model Intercomparison Project Phase 6 [CMIP6; (Eyring et al 2015); table S1].We estimated the occurrence and ToE of mega heatwaves (like the year 2022 heatwave) in the future climate.Besides maximum temperature, we also used minimum temperature (T min ) and soil moisture for the historical and future climate to examine the changes in future heat accumulation (GDDs).We regridded the CMIP6-GCMs projections at 0.25 • using the bilinear interpolation to maintain the consistency among the models for the analysis.The GMT (T mean ) was obtained from CMIP6-GCMs for the historical (1861-2014) and future (2015-2100) periods for all the four SSPs to identify the period (decades) for different warming levels (1.5 • , 2.0 • , 2.5 • , etc) in the future.We used the methodology described in King et al (2017) to identify the global warming levels in each CMIP6-GCM and emission scenario.King et al (2017) estimated global warming levels by calculating a certain level of rise in the GMT in a decade with respect to the GMT in the pre-industrial level .
We identified heatwaves using Russo et al (2015) method to analyze the heatwave frequency and duration in the observed  and future periods.Russo et al (2015) defined a heatwave spell when three or more than three consecutive days have a maximum temperature (T max ) above the 90th percentile of the daily maximum temperature threshold for the reference period .To identify any heatwave spell, first, we estimated the temperature difference (maximum temperature of given day minus 90th percentile threshold for the reference period) for each day during the observed period .Then, we identified the spell of consecutive 3 d or more having a positive temperature difference.Here, the 90th percentile threshold for a given calendar day was estimated based on a 30 d window as follows: where T maxy,n is the daily maximum temperature of the day n in the year y, and U denotes the union of sets.Using the above equation, the threshold value was evaluated for each day of the year to estimate the temperature difference.Moreover, we considered the reasonable sample size (30 year data) of temperature to calculate the threshold (Perkins and Alexander 2013).Further, the temperature difference (maximum temperature of given day minus 90th percentile threshold for the reference period) time series was used to identify the heatwave spells.
Using the heatwave spells, we estimated the trend in heatwave duration and frequency during the period 1950-2021.The trend in heatwave duration and frequency was calculated using the non-parametric Mann-Kendall (Mann 1945, Kendall 1975) test and Sen's slope method (Sen 1968).Moreover, we estimated the anomalies in mean temperature, SLP, geopotential height, and wind speed during the 2022 heatwave spell months (March and April).
To identify the severely affected region of South Asia during the year 2022 heatwave, we estimated maximum temperature anomaly with respect to the reference period of 1981-2010 for different durations (1-60 d) and selected the most severely affected area (T max anomaly exceeding 2 • C) of South Asia during the heatwave in 2022.In addition, we developed the intensity-duration-frequency (IDF) curves to understand the recurrence of the 2022 heatwave intensity during observed and future climate.We used the non-stationary generalized extreme value distribution (Agilan and Umamahesh 2017, Ali and Mishra 2018, Nanditha et al 2020) based on the annual block maxima [ABM (Ali and Mishra 2017)] approach for 1950-2021 to estimate the IDF curves for the severely affected region.Using the ABM approach, we calculated the annual maximum temperature anomaly (highest T max anomaly in a year) for the different durations (1, 3, 7, 15, 30, 45, and 60 d) using the areaaveraged daily maximum temperature data for the period 1950-2021.The non-stationary generalized extreme value (GEV) distribution using maximum likelihood estimates was used to estimate the return levels for different durations of the annual maximum temperature anomaly time series.In non-stationary GEV distribution, we considered the role of GMT in the regional maximum temperature anomaly time series (Agilan and Umamahesh 2017, Ali and Mishra 2018) and permitted linear changes in the location parameter (µ) with GMT [keeping the other two parameters (scale (σ), and shape (k)) constant].
In addition to analyzing the 2022 mega heatwave, we estimated the severity of mega heatwaves (like the year 2022) in the projected future climate.Therefore, we examined the changes in the frequency of mega heatwaves in the future warming climate under different SSPs.The mega heatwave was defined based on the intensity (mean T max anomaly) and duration of the heatwave spell.If the mean intensity and duration of any heatwave spell were equal and more than the 2022 heatwave, we defined that heatwave event as a mega heatwave.Further, we estimated the ToE of the mega heatwave when the occurrence of mega heatwave becomes consistent in the future warming climate.Initially, the ToE is defined in terms of the climate change signal-to-noise ratio to study temperature and precipitation change under global warming (Giorgi andBi 2009, Hawkins andSutton 2012).Recently, Satoh et al (2022) and Ma and Yuan (2023) used the terms 'time of first emergence (TFE)' or 'time of emergence (ToE)' to study unprecedented hydrological drought and heatwave, respectively.Here, we defined the ToE as the time at which the occurrence of a mega heatwave starts and frequently occurs after that time (Ma and Yuan 2023).To estimate the ToE of mega heatwaves, we evaluated the frequency of mega heatwaves in every 30 year moving time window from 2015 to 2100 under all four scenarios for each model and identified the time when the occurrence of mega heatwaves starts.We used the median value of the ToE of all the 21 CMIP6-GCMs for each scenario to represent the ToE of mega heatwave under each SSP.
We estimated the likelihood of mega heatwave based on the occurrence in the near (2031-2060) and far period (2071-2100) under all four scenarios.To analyze the large-scale impact of mega heatwaves in the densely populated South Asian region, we estimated the area and population affected by the mega heatwave in South Asia under different SSPs.We obtained the spatially explicit population data for different SSPs at 0.125 • spatial resolution (Jones and O'Neill 2016) from the integrated assessment modeling section of the National Center for Atmospheric Research for four different SSPs (SSP1, SSP2, SSP3, and SSP5).The raw population data were further aggregated at 0.25 • to maintain consistency with other datasets and to perform the analysis.

Heatwaves in South Asia during the observed period (1950-2022)
Most of the heatwaves in the South Asian region occur during the pre-monsoon season (Mishra et al 2017(Mishra et al , 2022)).Therefore, we estimated the heatwave characteristics over South Asia during the pre-monsoon (February-April) season for the period 1950-2022 (figure 1).First, we identified the heatwave spells and examined their characteristics over South Asia.Our results showed that the heatwave frequency and duration have substantially increased in the last seven decades ; figures 1(a) and (c)) over the majority region of South Asia except for the Indo-Gangetic plains.In the last decade (2010-2019), the South Asian region faced, on average, three heatwaves per year, which lasted around 15 d.However, the heatwave frequency and duration that occurred in the year 2022 were much larger than the average heatwave frequency and duration during the last decade (figure 1).
In 2022, the region faced five heatwaves during the pre-monsoon season for more than 30 d (36 d).The 2022 heatwave was the worst in South Asia during the pre-monsoon season in the entire record .Therefore, we further analyzed the intensity and areal extent of the 2022 heatwave.
In 2022, five heatwave spells occurred during March and April over South Asia for more than 30 d during the pre-monsoon season (from 12 March to 22 March; 27 March to 1 April; 5 April to 12 April; 15 April to 18 April; and 25 April to 30 April; figure 2(a)).The majority of South Asia (except part of the Indo-Gangetic plains and South India) experienced multiple heat spells (more than two heatwaves) for a total number of more than 20-30 d in 2022 (figures 2(b) and (c)).Since the duration of the 2022 heatwave varied from 1 d to more than 45 d across South Asia, we estimated the gridded heatwave intensity (using T max anomaly) for multiple durations (1, 3, 7, 15, 30, 45, and 60 d) to identify the areal extent and average intensity of the year 2022 heatwave (figure S1).The areal extent and intensity of the 2022 heatwave were increased with the duration (1-60 d), however, the highest areal extent and intensity were for the 60 d duration.Therefore, we used 60 d maximum temperature anomaly (during the pre-monsoon season) to represent the areal extent and intensity of the 2022 heatwave.The 60 d maximum temperature anomaly during pre-monsoon (February-April) for 2022 was more than 2 • C over the Northern, Western, and Central parts of South Asia, which was attributed to several heatwaves of longer duration (figures 2(d) and S1).The worst heatwave (rank 1) occurred during the year 2022 and covered about 60% of South Asia (figures 2(e) and S2).
Next, we estimated the IDF curves to evaluate the severity of the 2022 heatwave using the nonstationary GEV distribution during the observed period (1950-2021; figure S3).We estimated heatwave intensity (based on maximum temperature anomaly) for a 10-500 year return period for 1-60 d duration using the area-averaged maximum temperature anomaly of the period 1950-2021.The 2022 heatwave intensity had less than a 100 year return period for 1, 3, 7, and 15 d durations.However, we found around 500 year return period of the 2022 heatwave for 45 d and 60 d durations due to prolonged and intense heatwave spells.Since there were about five heatwaves that occurred for more than 30 d in 2022, the long-duration (45 and 60 d) heatwaves showed a higher return period.Overall, the pre-monsoon season of the year 2022 had the most exceptional heatwave (around 500 year return period) in the last 70 years (figure S3).

Impacts of the 2022 mega heatwave
To understand how the 2022 heatwave impacted agriculture and water availability in the region, we analyzed soil moisture and vegetation conditions over South Asia during March and April.We estimated soil moisture anomaly over South Asia for March and April 2022 using the reference period 1982-2021 (figures S4(a) and (b)).The 2022 heatwave caused abnormal soil moisture deficit in the western part of South Asia during March and April 2022, which resulted in drought in Pakistan.Soil moisture deficit and drought caused wildfires in the western region of Pakistan (DeAndreis 2022), resulting in the loss of hundreds of native olive trees (DeAndreis 2022).Northern and eastern parts of South Asia experienced vegetation stress (based on NDVI anomaly) during March and April 2022 that was associated with the heatwave.In addition, the heatwave also caused a 10%-30% reduction in the crop yield in Punjab and Haryana (Bal et al 2022, World Weather Attribution 2022a).However, heatwave impact on crop production was not visible in a large part of South Asia, mainly due to groundwater-based irrigation (figure S4).The intense and large areal extent of the 2022 heatwave caused more than 90 deaths across Pakistan and India (Basu 2022, DeAndreis 2022) and a long-hours power outage (TOI 2022; Varadhan 2022).Moreover, the 2022 heatwave accelerated the melting of Himalayan glaciers in Northern India and Pakistan due to the high-temperature rise in the region and led to increased glacial meltwater (Aftab 2022, Chaudhary and Clark 2022).

Atmospheric anomalies during the 2022 heatwave
We estimated the mean surface temperature, mean SLP, geopotential height (at 850 hPa), and wind speed (at 850 hPa) for the observed period  to examine the patterns of atmospheric circulation during the heatwave (figure 3).During the March and April months, most of the South Asian region remains hot (temperature above 30 • C) except the northern part of South Asia (Himalayan region, figure 3(a)).Therefore, the high temperature in the central and southern parts of South Asia causes lower pressure in the region, and wind flows from North to South during the normal pre-monsoon season (figures 3(a)-(c)).However, the atmospheric circulation was substantially different during the heatwave of the year 2022 (figures 3(d)-(f)).For instance, the western region of South Asia showed a large temperature anomaly during the March and April months of 2022, which caused lower mean SLP in the western part of South Asia.The lower mean SLP and high surface temperature resulted in reverse atmospheric circulation and anomalously high geopotential height over western India, Pakistan, and Afghanistan (figures 3(d)-(f)).The 2022 mega heatwave in South Asia was associated with the radiative heating of arid and semi-arid regions of western India, Pakistan, and Afghanistan, which resulted in a high geopotential height and low pressure over South Asia.Moreover, the anomalous high geopotential height over west South Asia blocked the Southern wind movement in the region, which caused the persistent and prolonged heatwave during March-April 2022 in South Asia.

Likelihood of the 2022 heatwave in the future
An increase in the frequency of mega heatwave (more severe than the year 2022 mega heatwave) is projected in the future warming climate under all four scenarios during the near (2031-2060) and far period (2071-2100; figure 4).The projected increase in the mega heatwave is most prominent under the SSP5-8.5 while the least under SSP1-2.6 for both near and far periods (figure 4).During the near period, the southern part of South Asia is more vulnerable than other parts under all four scenarios (figure 4).Therefore, the ToE is lower in the Southern part of South Asia (figure 4).Like the near period, the southern part of South Asia showed a higher increase in the mega heatwave frequency under SSP1-2.6 and SSP2-4.5.However, the North-western parts of South Asia showed a higher increase in the mega heatwave frequency under SSP3-7.0 and 5-8.5.Overall, the southern part of South Asia is more vulnerable to mega heatwaves in the near future, and the emergence of mega heatwaves is expected around 2040.Moreover, mega heatwaves are projected to increase largely in the northern and western parts of South Asia in the far future period (figure 4).
Since the projected rise in the mega heatwave frequency is the highest under the SSP5-8.5 and lowest under the SSP1-2.6 in the future, the average ToE is the earliest (in the year 2038) under SSP5-8.5 and the latest (in the year 2045) under SSP1-2.6 (figure 5(a)).In addition to ToE, the likelihood of mega heatwaves is projected to increase under all the scenarios due to an increase in the frequency of the mega heatwaves under climate change.Like the frequency of mega heatwave, the likelihood of the mega heatwave is the lowest (5%) under the SSP1-2.6 in the near period and highest (38%) under SSP5-8.5 in the far period (figure 5(b)).
We also estimated the area and population affected by mega heatwaves in the future under different scenarios (figure 5(c)).Like the frequency and likelihood of mega heatwaves, the area under mega heatwaves is projected to increase in the future.The area under mega heatwave is the lowest during the near period under SSP1-2.6 and highest during the far period under SSP5-8.5 (figure 5(c)).The population affected by mega heatwave is also projected to increase in the future, but due to less population in SSP5-8.5 compared to SSP3-7.0 (Samir and Lutz 2017), the population affected by mega heatwave is highest under SSP3-7.0 in the far period and lowest in the near period under SSP1-2.6.
We estimated the changes in the frequency and severity of mega heatwaves under the different warming levels (figures S5 and S6).The frequency of mega heatwaves is projected to increase as the warming level rises.Similarly, the heatwave severity is projected to increase in the 1.5 • , 2.0 • , and 2.5 • warming worlds compared to the historical climate due to increased frequency (figure S5).For instance, the return period of a heatwave of 3.9 • C maximum temperature anomaly (like the year 2022 heatwave) was more than 500 year for 45 and 60 d duration in the historical climate, while the same event showed less than 25 year return period under the 2.5 • warming world (figure S5).Overall, unprecedented heatwaves (like the 2022 mega heatwave) are projected to become frequent under the future warming climate in South Asia.

Heat accumulation in future warming
The changes in the frequency and severity of mega heatwaves in the future climate during pre-monsoon will affect the GDDs (heat accumulation) in the Rabi season (October-May) in South Asia, which can adversely affect the food production in the region (Kukal and Irmak 2018).Therefore, we estimated the changes in heat accumulation in the future over South Asia.As pre-monsoon mega heatwave affects the temperature and heat accumulation in the Rabi season, we evaluated the GDDs, which is the accumulated temperature value above base temperature (T mean − T base ) for the Rabi season, considering the base temperature 10 • C. Like changes in the mega heatwave frequency, the heat accumulation during the Rabi season is projected to increase under all four scenarios in the near and far future periods (figure 6).The heat accumulation is projected to increase the highest under SSP5-8.5 in the far period and lowest in the near period under SSP1-2.6 (figure 6).Moreover, heat accumulation is projected to increase maximum in the western part of South Asia, which can negatively affect food production in the western part of South Asia in the future period (figure 6).

Conclusions
The 2022 heatwave was unprecedented and the most intense in the observed period , severely affecting millions of people in South Asia.Moreover, similar mega heatwaves are projected to increase in the near future, which will enhance the heat accumulation in the region.Our findings can be used to develop a more resilient system for energy, water, and food availability in the region to address the severe challenges related to unprecedented mega heatwaves in the future warming climate.
Based on our analysis, the following conclusions can be made: 1. Using the gridded ERA5 data, we find an increasing trend in the heatwave spells and total duration in the period 1950-2021.Compared to the historical heatwave events, the total duration and spells of the 2022 heatwave were much larger than the average heatwave spells and duration that occurred during 1950-2021.2. In 2022, South Asia experienced an average of five consecutive heatwave spells for a total duration of more than 35 d.Moreover, the heatwave intensity analysis based on 60 d maximum temperature anomaly showed that the majority region of South Asia experienced exceptional heating with more than 3.9 • C rise in maximum temperature.
Based on the observational records, the 2022 heatwave was the most severe event (mega heatwave) with rank one that occurred over western, central, and eastern parts of South Asia.Moreover, the return period of the year 2022 heatwave was around 500 year for 45 and 60 d durations.3. Due to an intense prolonged temperature anomaly during March and April 2022, a deficit in soil moisture data was observed over Pakistan, which caused several wildfires in the region.The year 2022 heatwave spells also caused a negative impact on vegetation health and crop yield in Punjab and Haryana states, which are primary food-producing states in the region.4. The frequency of mega heatwave events is projected to increase under all four scenarios.Due to the frequent occurrence of mega heatwaves in the future climate, the ToE of mega heatwaves will be around the year 2030, considering all four scenarios, which will affect the large area and population of South Asia during 2071-2100.Moreover, the likelihood of mega heatwave events is projected to increase significantly under all scenarios during the near and far periods.5.The heat accumulation is projected to increase in the future climate over South Asia due to the increased mega heatwave risk in the region.The increased heat accumulation (GDD) will induce a more severe impact on the future water and food availability in the region.

Figure 1 .
Figure 1.Heatwave frequency and duration during the period (1950-2019).(a) The average number of heatwaves occurred in the recent decades (red bars) and 2022 (blue bars) in South Asia.(b) The trend in the Heatwave frequency during the period 1950-2019.(c) The average heatwave duration in recent decades (red bars) and 2022 (blue bar).(d) The trend in the Heatwave duration during the period 1950-2019.

Figure 2 .
Figure 2. The characteristics of the year 2022 heatwave.(a) The occurrence of heatwave spells in 2022 over South Asia using maximum temperature from ERA5.A heatwave spell is identified when three or more than three consecutive days show the maximum temperature above the daily threshold (90th percentile) for the reference period (1981-2010; Russo et al 2015).(b), (c) The total number of heatwave spells and duration of heatwaves (in day) that occurred in the year 2022 over the region.(d) The annual maximum Tmax anomaly of maximum temperature using 60 d moving mean in the year 2022.The region in the green line shows a more than 2 • C maximum temperature anomaly.(e) The rank of the year 2022 heatwaves based on 60 d moving annual maximum temperature anomaly.

Figure 3 .
Figure 3. Mean atmospheric circulation and atmospheric anomalies during March and April months.(a) Mean surface temperature, (b) mean sea level pressure, and (c) geopotential height with wind speed at 850 during pre-monsoon season for the reference period 1981-2010 over South Asia.(d) Temperature anomaly, (e) sea level pressure anomaly, and geopotential and wind anomalies (850 hPa) over South Asia during the year 2022 mega heatwave.

Figure 6 .
Figure 6.Changes in accumulated growing degree days (heat accumulation) over South Asia in the future climate during Rabi Season.(a), (b) Spatial distribution of changes in accumulated growing degree days during the near (2031-2060) and end (2071-2100) period over South Asia under SSP1-2.6.(c) 30 year moving mean changes in annual accumulated growing degree over South Asia under SSP1-2.6 for the period 2021-2071 using area-averaged temperature.Panels (d)-(f), (g)-(i), and (j)-(l) are the same as panels (a)-(c), but for SSP2-4.5,SSP3-7.0, and SSP5-8.5, respectively.The shaded area in the right column figures shows the uncertainty (±1 standard deviation) in the changes in accumulated growing degree days due to the multiple GCMs (21 GCMs).
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