LONDON, June 18, 2019 British scientists have identified a way in which President Trump could save thousands of American lives from the US heat peril. All he needs to do is honour the Paris Agreement of 2015 to keep global warming to “well below” 2°C above the planetary average that has endured for most of human history.

If the global thermometer is kept at the lowest possible level of a rise of 1.5°C – rather than the average rise of 3°C of human-triggered heating that the planet seems on course to experience by the end of the century − then this simple decision would prevent up to 2,720 extra deaths in any city that experienced the kind of potentially-deadly heatwave that comes along every thirty years or so, according to a new study in the journal Scientific Advances.

Researchers focused on 15 US cities from where records yielded reliable data that could answer questions about climate and health. These were Atlanta, Boston, Chicago, Dallas, Detroit, Houston, Los Angeles, Miami, New York City, Philadelphia, Phoenix, San Francisco, Seattle, St Louis and Washington DC.

They then used statistical tools to calculate the number of deaths that could be expected in the kind of extremely hot summers occasionally recorded in big cities at almost any latitude, and likely to recur with greater frequency and intensity as global average temperatures rise.

Poor face biggest risk

They found what they call “compelling evidence” that limiting global warming to 1.5°C would prevent significantly more excess deaths among the old, the poor or the already-ill in the US than a 2°C limit, and many more than the 3°C or more if governments continue on a “business as usual” course and humans burn even more fossil fuels, to emit ever more greenhouse gases into the atmosphere.

President Trump has promised to withdraw the US from the Paris Agreement signed by his predecessor, President Obama. But the study is a reminder that extremes of heat bring often devastating losses of life even in relatively well-off communities in the world’s temperate zones. Those most at risk remain the poorest urban dwellers in the world’s warmest places.

Researchers have warned that by 2100, one person in three in Africa’s cities could be exposed to intolerable levels of heat, and have identified other zones where heat and humidity could conspire to reach lethal levels: these include the North China plain and the Gulf region.

US scientists recently numbered 27 ways in which extremes of heat could claim lives and some of these are likely to apply to cities in the normally cooler parts of the globe.

Health authorities have identified deaths attributable to heat in London and Paris in 2003, and European scientists have warned that more murderous heat waves are on the way.

And although the Science Advances research concentrates on what could happen in American cities tomorrow, a second and separate study led by US scientists has just established a direct link between intense heat events and extra deaths in the Nevada city of Las Vegas, just in the last 10 years.

They report in the International Journal of Environmental Science and Technology that they found a steady increase in the severity and frequency of excess heat in the city since 1980, and a matching increase in numbers of deaths.

Between 2007 and 2016, there were 437 heat-related deaths in the city, with the greatest number in 2016, the year of the highest measures of heat for the past 35 years. − ClimateNewsNetworknet

Tim Radford, a founding editor of Climate News Network, worked for The Guardian for 32 years, for most of that time as science editor. He has been covering climate change since 1988.