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25 Apr 2023 | Press releases

Worst April heatwave in Asian history: Scientists urge action to avert catastrophic impacts across HKH

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With Bangladesh, China, India, Myanmar and Pakistan all hit by crippling heat as temperature records were broken across Asia this month, scientists at ICIMOD are urging global governments and businesses to make faster emissions reductions and development agencies to invest greater climate finance in efforts to accelerate adaptation for the region.

Temperatures on Monday (17 April) reached 41 degrees centigrade in Dhaka, Bangladesh, 45 degrees in Prayagraj, in India, and 44 in Kalewa, Myanmar. In China, Changsha and Fuzhou set the earliest local records for the commencement of summer, and several cities in Zhejiang Province broke their record for the highest daily temperature in April. On April 23 nine cities in Pakistan recorded temperatures of 40 and above.

The heat has resulted in deaths, schools closing and people being unable to work – compounding existing vulnerabilities, especially poverty and hunger, across the region.

“Human-induced climate change is the major cause of the growing number and ferocity of heat-waves we’re seeing across Asia. These signal to the fact that the climate emergency is here for this region,” says Deepshikha Sharma, a Climate and Environment Specialist at ICIMOD.

Abid Hussain, Senior Economist & Food Systems Specialist at ICIMOD says: “All climate models show that these spikes in heat are going to increase in frequency and intensity across South Asia. Such heat-waves will impact 2 billion people either directly, in terms of heat impacts on health and work, or indirectly in terms of glacier melt, floods, water variability, erratic rainfall and landslides.”

The heatwaves come as the United Nations State of the World Climate report shows Antarctic sea ice falling to its lowest extent on record and the melting of glaciers in the European Alps as “literally off the charts.”

The Hindu Kush Himalaya, which holds the third largest body of frozen water in the world, is warming at double the global average. Higher temperatures mean that glaciers melt faster and the resulting water flowing into rivers is less predictable. As temperatures continue to rise and glaciers get smaller, this leads to water scarcity and food insecurity in the region as well as increasing the likelihood of hazards such as flash floods. “Because of inadequate institutional and community capacity, most of these hazards are likely to turn into disasters,” says Hussain.

“In the most optimistic scenario, limiting global warming to 1.5 C, the region stands to lose one third of its glaciers by 2100 – creating huge risk to mountain communities, ecosystems and nature and the quarter of humanity downstream,” says Sharma. The rate of ice mass loss in the Hindu Kush Himalayas has consistently accelerated over the past six decades and glaciers even above 6,000 metres above sea level are thinning.

“Changes are now happening far faster than we feared and 1.5 degrees of warning is simply too hot,” says Sharma. “It is urgent that we make rapid and drastic progress in emissions reductions and scale adaptation finance, and for a much greater impact in adaptation and disaster risk reduction measures to protect the people and ecosystems, whose vulnerabilities are increasing by the day through no fault of their own.”

ICIMOD works with NASA, USAID and partners to monitor and predict regional droughts and extreme weather events through its SERVIR-HKH initiative. It shares this Regional Drought Monitoring and Outlook data with public bodies in our eight regional member countries.

Related publications

Study on the Water and Heat Fluxes of a Very Humid Forest Ecosystem and Their Relationship with Environmental Factors in Jinyun Mountain, Chongqing

The high‐humidity mountain forest ecosystem (HHMF) of Jinyun Mountain in Chongqing is a fragile ecosystem that is sensitive to climate change and human activities. Because it is shrouded in fog year‐round, illumination in the area is seriously insufficient. However, the flux (energy, wa-ter) exchanges (FEs) in this ecosystem and their influencing factors are not clear. Using one‐year data from flux towers with a double‐layer (25 m and 35 m) eddy covariance (EC) observation sys-tem, we proved the applicability of the EC method on rough underlying surfaces, quantified the FEs of HHMFs, and found that part of the fog might also be observed by the EC method. The observation time was separated from day and night, and then the environmental control of the FEs was determined by stepwise regression analysis. Through the water balance, it was proven that the negative value of evapotranspiration (ETN), which represented the water vapor input from the atmosphere to the ecosystem, could not be ignored and provided a new idea for the possible causes of the evaporation paradox. The results showed that the annual average daily sensible heat flux (H) and latent heat flux (LE) ranged from −126.56 to 131.27 W m−2 and from −106.7 to 222.27 W m−2, respectively. The annual evapotranspiration (ET), positive evapotranspiration (ETP), and negative evapotranspi-ration (ETN) values were 389.31, 1387.76, and −998.45 mm, respectively. The energy closure rate of the EC method in the ecosystems was 84%. Fog was the ETN observed by the EC method and an important water source of the HHMF. Therefore, the study area was divided into subtropical mountain cloud forests (STMCFs). Stepwise regression analysis showed that the H and LE during the day were mainly determined by radiation (Rn) and temperature (Tair), indicating that the energy of the ecosystem was limited, and future climate warming may enhance the FEs of the ecosystem. Addi-tionally, ETN was controlled by wind speed (WS) in the whole period, and WS was mainly affected by altitude and temperature differences within the city. Therefore, fog is more likely to occur in the mountains near heat island cities in tropical and subtropical regions. This study emphasizes that fog, as an important water source, is easily ignored in most EC methods and that there will be a large amount of fog in ecosystems affected by future climate warming, which can explain the evaporation paradox. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

Planning for climate resilience in Nepal: A training manual for local governments
Planning for climate resilience in Nepal: A training manual for local governments

Climate change-induced hazards, such as rising temperature, uncertain rainfall, heat stress, drought, and floods impose significant stresses on the Himalayan region, leading to disruption of infrastructure and other socio-ecological systems in urban and rural areas. To address such challenges, ICLEI South Asia and ICIMOD have jointly developed a training manual for the local authorities as well as decision-makers and practitioners to prepare a climate resilience strategy that can address climate mitigation and adaptation aspects through consultative participation of local stakeholders. The manual is developed under the Climate and Development Knowledge Network programme.

Climate change and spatio-temporal trend analysis of climate extremes in the homogeneous climatic zones of Pakistan during 1962-2019
Climate change and spatio-temporal trend analysis of climate extremes in the homogeneous climatic zones of Pakistan during 1962-2019

Climate extremes, such as heat waves, droughts, extreme rainfall can lead to harvest failures, flooding and consequently threaten the food security worldwide. Improving our understanding about climate extremes can mitigate the worst impacts of climate change and extremes. The objective here is to investigate the changes in climate and climate extremes by considering two time slices (i.e., 1962–1990 and 1991–2019) in all climate zones of Pakistan by utilizing observed data from 54 meteorological stations. Different statistical methods and techniques were applied on observed station data to assess changes in temperature, precipitation and spatio-temporal trends of climatic extremes over Pakistan from 1962 to 2019. The Mann-Kendal test demonstrated increasing precipitation (DJF) and decreasing maximum and minimum temperatures (JJA) at the meteorological stations located in the Karakoram region during 1962–1990. The decadal analysis, on the other hand, showed a decrease in precipitation during 1991–2019 and an increase in temperature (maximum and minimum) during 2010–2019, which is consistent with the recently observed slight mass loss of glaciers related to the Karakoram Anomaly. These changes are highly significant at 5% level of significance at most of the stations. In case of temperature extremes, summer days (SU25) increased except in zone 4, TX10p (cold days) decreased across the country during 1962–1990, except for zones 1 and 2. TX90p (warm days) increased between 1991–2019, with the exception of zone 5, and decreased during 1962–1990, with the exception of zones 2 and 5. The spatio-temporal trend of consecutive dry days (CDD) indicated a rising tendency from 1991 to 2019, with the exception of zone 4, which showed a decreasing trend. PRCPTOT (annual total wet-day precipitation), R10 (number of heavy precipitation days), R20 (number of very heavy precipitation days), and R25mm (very heavy precipitation days) increased (decreased) considerably in the North Pakistan during 1962–1990 (1991–2019). The findings of this study can help to address some of the sustainable development goals related climate action, hunger and environment. In addition, the findings can help in developing sustainable adaptation and mitigation strategies against climate change and extremes. As the climate and extremes conditions are not the uniform in all climate zone, therefore, it is suggested to the formers and agriculture department to harvest crops resilient to the climatic condition of each zone. Temperature has increasing trend in the northern Pakistan, therefore, the concerned stakeholders need to make rational plans for higher river flow/flood situation due to snow and glacier melt. Copyright: © 2022 Khan et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Environmental impacts of shifts in energy, emissions, and urban heat island during the COVID-19 lockdown across Pakistan
Environmental impacts of shifts in energy, emissions, and urban heat island during the COVID-19 lockdown across Pakistan

Restrictions on human and industrial activities due to the coronavirus (COVID-19) pandemic have resulted in an unprecedented reduction in energy consumption and air pollution around the world. Quantifying these changes in environmental conditions due to government-enforced containment measures provides a unique opportunity to understand the patterns, origins and impacts of air pollutants. During the lockdown in Pakistan, a significant reduction in energy demands and a decline of ∼1786 GWh (gigawatt hours) in electricity generation is reported. We used satellite observational data for nitrogen dioxide (NO2), carbon monoxide (CO), sulphur dioxide (SO2), aerosol optical depth (AOD) and land surface temperature (LST) to explore the associated environmental impacts of shifts in energy demands and emissions across Pakistan. During the strict lockdown period (March 23 to April 15, 2020), we observed a reduction in NO2 emissions by 40% from coal-based power plants followed by 30% in major urban areas compared to the same period in 2019. Also, around 25% decrease in AOD (at 550 nm) thickness in industrial and energy sectors was observed although no major decrease was evident in urban areas. Most of the industrial regions resumed emissions during the 3rd quarter of April 2020 while the urban regions maintained reduced emissions for a longer period. Nonetheless, a gradual increase has been observed since April 16 due to relaxations in lockdown implementations. Restrictions on transportation in the cities resulted in an evident drop in the surface urban heat island (SUHI) effect, particularly in megacities. The changes reported as well as the analytical framework provides a baseline benchmark to assess the sectoral pollution contributions to air quality, especially in the scarcity of ground-based monitoring systems across the country.

Mapping the aerodynamic roughness of the Greenland Ice Sheet surface using ICESat-2: Evaluation over the K-transect
Mapping the aerodynamic roughness of the Greenland Ice Sheet surface using ICESat-2: Evaluation over the K-transect

The aerodynamic roughness of heat, moisture, and momentum of a natural surface are important parameters in atmospheric models, as they co-determine the intensity of turbulent transfer between the atmosphere and the surface. Unfortunately this parameter is often poorly known, especially in remote areas where neither high-resolution elevation models nor eddy-covariance measurements are available. In this study we adapt a bulk drag partitioning model to estimate the aerodynamic roughness length (z0m) such that it can be applied to 1D (i.e. unidirectional) elevation profiles, typically measured by laser altimeters. We apply the model to a rough ice surface on the K-transect (west Greenland Ice Sheet) using UAV photogrammetry, and we evaluate the modelled roughness against in situ eddy-covariance observations. We then present a method to estimate the topography at 1 m horizontal resolution using the ICESat-2 satellite laser altimeter, and we demonstrate the high precision of the satellite elevation profiles against UAV photogrammetry. The currently available satellite profiles are used to map the aerodynamic roughness during different time periods along the K-transect, that is compared to an extensive dataset of in situ observations. We find a considerable spatio-temporal variability in z0m, ranging between 10−4 m for a smooth snow surface and 10−1 m for rough crevassed areas, which confirms the need to incorporate a variable aerodynamic roughness in atmospheric models over ice sheets

Energy and mass balance dynamics of the seasonal snowpack at two high-altitude sites in the Himalaya
Energy and mass balance dynamics of the seasonal snowpack at two high-altitude sites in the Himalaya

Snow dynamics play a crucial role in the hydrology of alpine catchments in the Himalaya. However, studies based on in-situ observations that elucidate the energy and mass balance of the snowpack at high altitude in this region are scarce. In this study, we use meteorological and snow observations at two high-altitude sites in the Nepalese Himalaya to quantify the mass and energy balance of the seasonal snowpack. Using a data driven experimental set-up we aim to understand the main meteorological drivers of snowmelt, illustrate the importance of accounting for the cold content dynamics of the snowpack, and gain insight into the role that snow meltwater refreezing plays in the energy and mass balance of the snowpack. Our results show an intricate relation between the sensitivity of melt and refreezing on the albedo, the importance of meltwater refreezing, and the amount of positive net energy used to overcome the cold content of the snowpack. The net energy available at both sites is primarily driven by the net shortwave radiation, and is therefore extremely sensitive to snow albedo measurements. We conclude that, based on observed snowpack temperatures, 21% of the net positive energy is used to overcome the cold content build up during the night. We also show that at least 32–34% of the snow meltwater refreezes again for both sites. Even when the cold content and refreezing are accounted for, excess energy is available beyond what is needed to melt the snowpack. We hypothesize that this excess energy may be explained by uncertainties in the measurement of shortwave radiation, an underestimation of refreezing due to a basal ice layer, a cold content increase due to fresh snowfall and the ground heat flux. Our study shows that in order to accurately simulate the mass balance of seasonal snowpacks in Himalayan catchments, simple temperature index models do not suffice and refreezing and the cold content needs to be accounted for.

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