Authors: Kristie L Ebi, University of Washington, Yun-Chul Hong, Seoul National University and Alistair Woodward, Auckland University
Surface air temperatures over land have increased by around 1.5 degrees Celsius in the last 150 years, leading to adverse impacts on human health and well-being. Further warming will magnify these risks, depending on the extent of emissions reduction and investment in building climate-resilient health systems.
Asia is particularly vulnerable due to increased exposure to the consequences of climate change. It is projected to experience increases in ambient temperatures, extreme precipitation events and sea level rise. These will have health consequences, including temperature-related morbidity and mortality, injuries and deaths from extreme weather events, vector-borne diseases and undernutrition.
Asia has already experienced an increase in the frequency and intensity of extreme weather events such as tropical cyclones, ﬂoods, droughts and heatwaves, resulting in significant numbers of injuries and deaths. The region is particularly at risk because of the large and growing populations, long coastlines, abundant low-lying areas and reliance on the agricultural sector and natural resources. Increasing unpredictability of the annual monsoon is of particular concern in Southeast Asia. These vulnerabilities amplify climate-related risks in many countries.
Compounding of extreme weather events, such as high temperatures coinciding with cyclones or back-to-back heatwaves, are also of particular concern and will occur with increasing frequency.
Under most scenarios, rising temperatures will expose large populations to health-damaging heatwaves throughout Asia. Risks will be especially severe in densely populated cities and agricultural areas of South Asia and eastern China. Higher average temperatures reduce productivity of outdoor workers, and can also adversely affect maternal and child health.
Successful heat action plans have been implemented in India, China and other countries. These need to be regularly reviewed as the onset, severity and duration of dangerously high temperatures change. Improved access to air conditioning is part of heat adaptation in many settings but is not feasible at the scale required to protect entire populations.
Vector-borne diseases, particularly mosquito-borne diseases, are a major public health problem in Asia, with malaria, dengue fever and chikungunya at endemic levels in the region. Climate change affects ambient temperatures and precipitation levels in ways that are generally beneficial for mosquito populations, increasing their geographic range and extending transmission seasons for these diseases. Recurrent outbreaks pose significant health threats, as evidenced during the early years of the 21st century.
Warming temperatures, changing precipitation patterns and greater frequency of droughts and desertification have compromised food security in parts of Asia. Although climate change has increased crop yields in some high mountain regions, yields in lower-latitude regions have been negatively affected. Increased atmospheric carbon dioxide levels can lower the nutritional quality of crops. More frequent extreme weather events will also disrupt supply chains. With cereal prices projected to increase by 2050, the region’s most vulnerable people face food insecurity and hunger. Southeast Asia has already seen an increase of stunting in children.
Although frequently overlooked, mental health problems are common throughout Asia, and are amplified by stresses associated with climate change. Acute, climate-related events can lead to mental distress, which may manifest as anxiety, mood disorders and social withdrawal, and can increase suicide risk. Prolonged and repeated droughts have been associated with depression and self-harm, especially among farmers. Long-term climate change also undermines the sense of place that is foundational to mental well-being in all populations, and especially in indigenous cultures; sea-level rise in the Pacific is a well-documented example.
Shortening return periods between extreme weather events threatens the capacity of societies and individuals to recover confidence and promote mental healing. The compounding and increasingly negative effects of repeated COVID-19 lockdowns on morale and well-being illustrate this phenomenon.
Modelling suggests the most effective way of reducing the number of people vulnerable to climate change is through sustainable development that actively reduces socioeconomic inequality and poverty in Africa and Asia.
One analysis looked at the interplay between socioeconomic development and 14 climate change risks to water, energy and land sectors, including exposure to extreme heat events. Global exposure to multisector risk was projected to double, with a 1.5–2 degrees Celsius warming and then double again with a 3 degrees Celsius increase. With a 1.5–2 degrees Celsius increase, the total population exposed to multisectoral risks increased by 69–113 per cent and the level of exposure increased by 60–258 per cent. Most of the risk was in Asia and Africa.
The magnitude and pattern of future injuries, illnesses and deaths associated with climate change depend on the level of warming and on the socioeconomic development pathway followed. Pathways with higher population growth, high levels of consumption, limited investments in technology development and a low ability to adapt will magnify the health risks of climate change.
A comprehensive approach is needed to manage these risks, requiring scientists, policymakers, funding-source managers and the public to work together to address the impacts of climate change and build resilient communities. This requires well-coordinated, multisectoral actions with the active participation of individuals and communities at risk. Innovative policies based on sound science, political will and sustainable financing, supported and coordinated by international organisations like the World Health Organization, are essential for preparing for and managing the health risks of a warming planet.
Kristie L Ebi is Professor of Global Health and Environmental and Occupational Health Sciences at the Department of Global Health, the University of Washington.
Yun-Chul Hong is Professor at the Institute of Environmental Medicine and the Department of Preventive Medicine, Seoul National University College of Medicine.
Alistair Woodward is Professor of Epidemiology and Biostatistics at the School of Population Health, the University of Auckland.