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783. Record High Temperatures Observed in Asia in April Linked to Climate Change

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783. Record High Temperatures Observed in Asia in April Linked to Climate Change

According to World Weather Attribution, record high temperatures were observed in Bangladesh, India, Thailand, and Laos in late April 2023. A collaboration of scientists from India, Thailand, France, Australia, Denmark, Germany, Kenya, the Netherlands, the United States, and the United Kingdom assessed the occurrence of climate change-related heat waves for the four countries where temperature records were broken and loss of life was reported.

Heat waves with high humidity feel hotter than the actual temperatures. So the scientists used a heat index (in °C) that integrates temperature and humidity to analyze how climate change has changed the likelihood and intensity of heat waves over four days in April.

The following is a list of key findings relevant to climate change.

  • High temperature and humidity events, which have warmed about 1.2°C since the industrial revolution, are common in India and Bangladesh, but rare in Thailand and Laos.
  • Temperatures exceeded the "dangerous" threshold (41°C) in most of the South Asian regions studied. In some areas, temperatures approached the "extremely dangerous" level (above 54°C), where it is difficult to maintain body temperature.
  • To determine the impact of the 1.2°C temperature increase due to global warming on the heat wave, climate models were combined with observations to estimate the likelihood and intensity of a heat wave with high humidity, as observed in April.
  • Climate change has increased the likelihood of hot and humid conditions in India and Bangladesh by at least a factor of 30. At the same time, a five-year heat wave in India and Bangladesh makes the country about 2°C hotter on the heat index than it would be in the absence of warming.
  • In Thailand and Laos, humid heat waves (1 in 200 years) resulted in a heat index 2.3°C higher. On the other hand, if there had been no warming, the heat waves would not have occurred.
  • High temperatures and humidity are expected to continue due to global warming. In Thailand and Laos, a warming of 2°C above pre-industrial levels (0.8°C above current levels) would increase the likelihood of heat waves by about 10 times. In India and Bangladesh, the likelihood increases about threefold, with hot and humid events expected every 1-2 years.

The scientists also found that people who are physiologically vulnerable to hot and humid weather (e.g., due to pre-existing conditions, age, disability) and those who are susceptible due to their occupation (e.g., outdoor workers, farmers) are at the highest health risk. They also report that India has the most advanced heat-wave preparedness, with a reduction in heat-wave deaths in areas that have actually implemented solutions such as self-protective behaviors, heat early warning systems, passive and active cooling, urban planning, and heat action plans. On the other hand, the report notes that these solutions often fail to reach the most vulnerable populations and are likely to exacerbate the impacts of ongoing climate change on those already severely disadvantaged in their daily lives, requiring comprehensive adaptation and development interventions.


Extreme humid heat in South Asia in April 2023, largely driven by climate change, detrimental to vulnerable and disadvantaged communities (World Weather Attribution)

Contributor: KANAMORI Norihito (Information and Public Relations Office)


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