Compound heat extremes are increasing in eastern China

The effect that heat extremities have on humans is well documented, with the vast majority of worldwide regions seeing an increase in the intensity of such weather extremes due to global warming. However, the frequency of such events is also increasing, resulting in what is known as compound heat extremes.

Compound heat is when heat extremes occur consecutively over day and night, as opposed to occasionally during day or night. Unfortunately, research in this area is currently lacking, and not much is known about how often this is happening and how it is affecting society. It is a particularly large problem in the eastern regions of China.

A new study from the Institute of Atmospheric Physics (IAP) at the Chinese Academy of Sciences has investigated exactly this, revealing just how compound heat extremes affect human health. The researchers also investigated the drivers of compound heat extremes, as well as the future risk they impose on the cities of Eastern China.

The results suggest that compound heat extremes present significantly higher danger than solely day or night heat, particularly within the demographic of females and elderly residents.

Between 1961 and 2014, heat extremes in urban areas have increased in eastern China by 1.76 days per decade. The source of this could clearly be traced to the urbanization of the region in addition to anthropogenic emissions such as aerosols and greenhouse gases.

Urbanization was estimated to contribute to 0.51 days per decade, with greenhouse gases contributing 1.63 and other anthropogenic forcings by -0.54. However, without mitigation efforts toward future emissions and urbanization, these severe events could further increase in frequency by up to five times. This would ultimately lead to urban population exposure growth of between three and six times.

“Our study reveals that the public health risks from anthropogenic increases in compound hot extremes have been increasing and will continue to increase over cities in eastern China,” explained study lead author Dr. Jun Wang.

The age-specific vulnerabilities that have been uncovered by the study present further implications of elevated health burdens. This is mainly due to the urban population of eastern Chinese regions increasing in age overall.

The study was supported jointly by the National Key Research and Development Programme of China and the Strategic Priority Research Program of the Chinese Academy of Sciences. 

The study is published in the journal Nature Climate Change.

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By Calum Vaughan, Earth.com Staff Writer