Killer heatwaves set for dramatic rise, researchers warn

BHUBANESWAR, India - Nearly one in three people around the world is already exposed to deadly heatwaves, and that will rise to nearly half of people by 2100 even if the world moves aggressively to cut climate-changing emissions, scientists warned Monday.

If emissions continue to rise at their current pace, however, three in four people in the world will face deadly heat by the turn of the century, a study published in the journal Nature Climate Change said.

"People are talking about the future when it comes to climate change, but what we found from this paper is that this is already happening … and this is obviously going to get a lot worse," said Camilo Mora, lead author of the study and a geography professor at the University of Hawaii at Manoa.

By 2100, for instance, New York is likely to experience around 50 days a year with combined temperature and humidity exceeding the threshold in which people have previously died, researchers said.

In already hot southern U.S. cities such as Orlando and Houston, deadly heatwaves could last nearly the entire summer period, the study found.

But the most serious risks will be in tropical areas, where temperatures are already closer to the danger threshold and where heat can last more of the year, rather than just during the summer, researchers said.

"Warming at the poles has been one of the iconic climatic changes. Our study shows, however, that it is warming in the tropics what will pose the greatest risk," said Iain Caldwell, a co-author of the report and a researcher at the University of Hawaii at Manoa.

With temperatures already high, "it takes very little warming for conditions to turn deadly in the tropics," he said in a statement.

MORE HEATSTROKE, LESS WORK

In steamy Bhubaneswar, for instance, in eastern India's Odisha state, gardener Basudev Singh is bathed in sweat after two hours of early morning weeding, despite the temperature gauge showing 35 degrees Celsius (95 degrees Farenheit) – usually considered a bearable temperature in this part of India.

The problem is that the relative humidity is 82 percent, meaning the "real feel" of conditions is above 44 degrees Celsius (111 degrees Farenheit), experts say – and it's not yet even noon. Monsoon showers, which would normally cool the city, are past due.

The 27-year-old labourer said that over the last two and a half summer months he has lost close to half his average earnings because it has become impossible to work outside in searing heat.

Jitendra Murmu, another daily-wage worker, said efforts to move work to cooler parts of the day were becoming less effective.

"Over summer we even rescheduled our work timing because no work for three months means no food for our children," he said. "By early April we would rush to work at 5:30 a.m. when day broke, return home at 10:30 a.m. and resume at 3 in the afternoon, until sunset."

"But work itself is less available. Employers and construction contractors are themselves taking it slow due the heat," he said.

Mami Patra, the owner of a small medicine shop in central Bhubaneswar, said she has seen demand for heatstroke treatments surging.

"Every single day, all this summer, we get at least seven people who come to us complaining of exhaustion and asking for glucose powder packets," she said.

City doctors said the number of patients turning up with dizziness, confusion and vomiting – symptoms of heat exhaustion, a precursor to deadly heatstroke – is increasing, with patients 50 to 70 years old seemingly most affected.

Mora, the author of the University of Hawaii study, noted that the impacts of rising heat will extend far beyond simply a higher death toll, to things like "people having to take longer breaks to withstand the heat and compensate for it by working longer hours".

The already substantial heat death rate "also points out the limitation of many of these governments to afford the cost of adaptation," he said in an interview with the Thomson Reuters Foundation.

BAD - OR TERRIBLE?

The University of Hawaii study looked at nearly 2,000 deadly heatwave events since 1980, and focused in on more than 780 cases with particularly good data, gathered from 164 cities – from London to Sydney to Sao Paulo – spread across 36 countries.

Those included events such as a European heatwave in 2003 linked to 70,000 deaths, a 2010 Moscow heatwave that killed about 10,000 people and a 1995 Chicago heatwave that claimed 700.

The study identified consistent threshold levels of combined heat and humidity that triggered deaths, and used those to project future deadly heatwaves as world temperatures continue to rise as a result of climate change.

The area of the world where such a thresholds are crossed for 20 or more days a year has been increasing, and is projected to grow, even with dramatic cuts in greenhouse gas emissions, the researchers said.

"The scary thing is how common those deadly conditions are already," said Farrah Powell, a graduate student and one of the co-authors of the study, in a statement.

When heat and humidity exceed a person's core body temperature – about 37 degrees Celsius, or 98.6 degrees Farenheit – they person cannot dissipate heat into the environment, researchers said.

High humidity makes efforts so sweat out heat less effective, which can lead to a lethal build-up of body heat that can damage major organs, muscles and the brain.

"Climate change has put humanity on a dangerous path that will become increasingly dangerous and difficult to reverse if greenhouse gas emissions are not taken much more seriously," Mora said.

"We are running out of good choices for the future," he warned. "For heatwaves, our options are now between bad or terrible."