Sat, Aug 04, 2018 - Page 9 News List

Killer heatwaves could strike China
in its heart by the end of the century

The North Chinese Plain, the most populous region of the biggest polluter on Earth, could become uninhabitable in places if climate change continues, causing dangerous heatwaves that combine high temperatures with extreme humidity, researchers found

By Damian Carrington  /  The Guardian

Illustration: Tania Chou

The deadliest place on the planet for extreme future heatwaves will be the North China Plain, one of the most densely populated regions in the world and the most important food-producing area in China.

New scientific research shows that humid heatwaves that kill even healthy people within hours will strike the area repeatedly toward the end of the century due to climate change, unless there are heavy cuts in carbon emissions.

“This spot is going to be the hottest spot for deadly heatwaves in the future,” said Massachusetts Institute of Technology professor Elfatih Eltahir, who led the study.

The projections for China’s northern plain are particularly worrying because many of the region’s 400 million people are farmers and have little alternative to working outside.

“China is currently the largest contributor to the emissions of greenhouse gases, with potentially serious implications to its own population,” he said. “Continuation of current global emissions may limit the habitability of the most populous region of the most populous country on Earth.”

The analysis assessed the consequences of climate change for the deadly combination of heat and humidity, which is measured as the wet-bulb temperature (WBT). Once the WBT reaches 35°C, the air is so hot and humid that the human body cannot cool itself by sweating and even fit people sitting in the shade die within six hours.

A WBT above 31°C is classed by the US National Weather Service as “extreme danger,” with its warning stating: “If you don’t take precautions immediately, you may become seriously ill or even die.”

The research, published in the journal Nature Communications, found that fatal WBTs of 35°C could strike the North China Plain repeatedly between 2070 and 2100, unless carbon emissions are cut.

Shanghai, for example, would exceed the fatal threshold about five times and the “extreme danger” WBTs would occur hundreds of times. Even if significant carbon cuts are made, the “extreme danger” WBT would be exceeded many times.

Previous research by Eltahir and colleagues showed that the Persian Gulf in the Middle East, the heartland of the global oil industry, would also experience heatwaves beyond the limit of human survival if climate change is unchecked, particularly in Abu Dhabi, Dubai, Doha and coastal cities in Iran.

The fatal 35°C WBT was almost reached in Bandar Mahshahr, Iran, in July 2015, where 46°C heat combined with 50 percent humidity.

The scientists analyzed South Asia last year and found that it, too, is at risk of killer 35°C WBT heatwaves in places.

Even outside the extreme hotspots, three-quarters of the region’s population of 1.7 billion — particularly people farming in the Ganges and Indus valleys — would be exposed to “extreme danger” levels of humid heat toward the end of the century.

However, the North China Plain is set to be the worst place.

“The response [to climate change] is significantly larger than in the other two regions,” Eltahir said.

Signs of that future have already begun, with the study finding a substantial increase in extreme heatwaves on the plain over the past 50 years.

In 2013, a severe heatwave in the region persisted for 50 days, during which Shanghai broke a 141-year temperature record.

UK Centre for Ecology and Hydrology professor Chris Huntingford, who was not involved in the study, said: “The research finds that if greenhouse emissions continue at current levels, there will be many more days when unsafe thresholds are crossed. This will make work outdoors almost impossible across much of the agricultural regions of China.”

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