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Climate change to cause humid heatwaves that will kill even healthy people

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Extreme heatwaves that kill even healthy people within hours will strike parts of the Indian subcontinent unless global carbon emissions are cut sharply and soon, according to new research.

Even outside of these hotspots, three-quarters of the 1.7bn population – particularly those farming in the Ganges and Indus valleys – will be exposed to a level of humid heat classed as posing “extreme danger” towards the end of the century.

The new analysis assesses the impact of climate change on the deadly combination of heat and humidity, measured as the “wet bulb” temperature (WBT). Once this reaches 35C, the human body cannot cool itself by sweating and even fit people sitting in the shade will die within six hours. The revelations show the most severe impacts of global warming may strike those nations, such as India, whose carbon emissions are still rising as they lift millions of people out of poverty….

The limit of survivability, at 35C WBT, was almost reached in Bandar Mahshahr in Iran in July 2015, where 46C heat combined with 50% humidity. “This suggests the threshold may be breached sooner than projected,” said the researchers. 

The report demonstrates the urgency of measures to both cut emissions and help people cope better with such heatwaves, he said. There are uncertainties in the modelling – which Schär noted could underestimate or overestimate the impacts – as representing monsoon climates can be difficult and historical data is relatively scarce.

Prof Chris Huntingford, at the UK Centre for Ecology and Hydrology, said: “If given just one word to describe climate change, then ‘unfairness’ would be a good candidate. Raised levels of carbon dioxide in the atmosphere are expected to cause deadly heatwaves for much of South Asia. Yet many of those living there will have contributed little to climate change.

Eun-Soon Im, Jermey S. Pal and Elfatih A.B. Eltahir. Deadly heat waves projected in the densely populated agricultural regions of South Asia. Science Advances 02 Aug 2017: Vol. 3, no. 8, e1603322 DOI: 10.1126/sciadv.1603322

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