PARIS • An increase in global warming from 1.5 deg C to 2 deg C above late 19th-century levels would cause tens of thousands of extra deaths in China's cities every year, researchers have reported.
Even assuming future adaptations to cope with scorching heat - better public health services, more air-conditioning, easy access to clean drinking water - the half-degree bump in temperature would likely result in some 30,000 additional heat-related deaths a year, they reported in the journal Nature Communications.
Without those improvements in infrastructure and preparedness, excess mortality would go up another 50 per cent.
"Our study quite clearly demonstrates the benefits of limiting global warming to 1.5 deg C," co-author Buda Su, a scientist at Xinjiang Institute of Ecology and Geography in Urumqi, told Agence France-Presse.
Average global temperatures have already risen 1 deg C above the pre-industrial benchmark, enough to trigger longer and more intense droughts and heatwaves.
The start of the 21st century has seen several especially lethal heatwaves. The one that gripped Europe in 2003 resulted in more than 70,000 deaths above what would have been expected in a typical mid-to-late 20th-century year.
Unprecedented high temperatures in western Russia, including in Moscow, led to more than 50,000 excess deaths in the summer of 2010.
Last month was the hottest month across the globe ever recorded, and June saw a rash of record temperatures in the Northern Hemisphere.
China's land mass has warmed more quickly than the global average and is vulnerable to other environmental stresses such as water shortages.
Few studies have projected excess mortality in developing countries under different global warming scenarios, and even fewer have taken into account differences of sex and age.
To create a baseline, a dozen researchers led by Nanjing University of Information Science and Technology researcher Yanjun Wang calculated heat-related mortality in 27 Chinese cities from 1986 to 2005.
Averaged across the country, they found that hot spells accounted each year for the death of 32 people per million.
Even in the highly optimistic scenario of a 1.5 deg C ceiling on global temperatures, the death rate in China will likely rise to between 49 and 67 people per million - assuming improved infrastructure and capacity.
Mortality rates for women have been, and are projected to be, nearly double those for men.