Killer Heat Waves Will Threaten Majority of Humankind by Century's End


By 2100, if nations continue to burn fossil fuels at the current rates, three out of four people will be at risk from lethal heat waves.

And even if the governments of the world act on promises they made in 2015 and drastically reduce greenhouse gas emissions, almost one in two could face the risk of sickness and death by intolerable heat.

That is because, as the temperatures rise, heat and humidity begin to challenge human physiology. Humans are adapted to body temperatures of around 37°C. If humidity—the levels of water vapour in the air—go up with the thermometer, then people caught in a zone of extreme heat cannot adjust body temperatures by perspiration.

And with every 1°C rise in temperatures, the capacity of the air to hold moisture goes up by 7 percent. People with no access to air conditioning or a cool breeze become at high risk.

It happened in Europe in 2003, when an estimated 70,000 died. A heat wave in Moscow in 2010 killed around 10,000. And researchers warned years ago that under global warming predictions, more such extremes of heat would become inevitable by 2020.

“We are running out of choices for the future,” said Camilo Mora, a geographer at the University of Hawaii at Manoa, who led the study.

“For heat waves, our options are now between bad or terrible. Many people around the world are already paying the ultimate price of heat waves, and while models suggest that this is likely to continue, it could be much worse if emissions are not considerably reduced.

“The human body can only function within a narrow range of core body temperatures around 37°C. Heat waves pose a considerable risk to human life because hot weather, aggravated with high humidity, can raise body temperature, leading to life-threatening conditions.”

Dr. Mora and colleagues warned years ago that by 2016 climate would change inexorably in at least some regions of the globe. More recently he and colleagues calculated that the relentless increase in carbon dioxide levels in the atmosphere could limit the growing season and pose a threat to world food security. History has yet to deliver a verdict on either prediction.


But the warning about heat waves starts from facts already available. One scientific group has calculated the humidity and temperature hazards and predicted that at least one climate zone—the Gulf between Iran and the Arabian Peninsula—could become murderously hot by the century’s end.

A second study of heat waves over recent decades in India has established a link between extremes of heat, climate change and mass death.

Dr. Mora and colleagues in the U.S. and Britain report in Nature Climate Change that they found evidence on a global scale. They began with 30,000 relevant publications and identified 911 scientific papers with data on 1,949 case studies of cities or regions where deaths were associated with high temperatures.

From this mass of information they found 783 lethal heat waves in 164 cities across 36 countries, with most cases recorded in developed countries at mid-latitudes since 1980: in cities such as New York, Washington, Los Angeles, Chicago, Toronto, London, Beijing, Tokyo, Sydney and São Paulo.

Risk mapped

From this data, they found a common threshold at which temperatures and humidities became lethal: that is, as relative humidity climbed, even lower temperatures could kill. And then they devised a world map of those cities and regions most at risk

Right now, one human in three lives in a climate zone in which death by extreme heat is or could be possible. The area in which such conditions are liable to happen on at least 20 days a year is predicted to grow.

By 2100 New York could have around 50 days in which conditions could be potentially lethal. In Sydney, Australia the number of such deadly days could be 20, for Los Angeles 30.

For Orlando, Florida, and Houston, Texas, the entire summer could exceed the thresholds at which people have been known to die.

“People are talking about the future when it comes down to climate change, but what we found from this paper is that this is already happening. In fact since 1980 we found close to 2,000 cases of these places and cities when people died from this, and this is obviously going to get a lot worse,” Dr. Mora said.

U.S. walk-out

Notoriously, President Trump has announced that he will withdraw the U.S. from the Paris Agreement of 2015 to contain average global warming to well below 2°C by the century’s end.

The implication of the Hawaiian research is that if nations act in a concerted way to reduce fossil fuel emissions, an estimated 48 percent of the human population could be at risk of summer extremes. And if they do not, this hazard rises to 74 percent.

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

“Action like the withdrawal from the Paris Agreement is a step in the wrong direction that will inevitably delay fixing a problem for which there is simply no time to waste.” 

Understand the importance of honest news ?

So do we.

The past year has been the most arduous of our lives. The Covid-19 pandemic continues to be catastrophic not only to our health - mental and physical - but also to the stability of millions of people. For all of us independent news organizations, it’s no exception.

We’ve covered everything thrown at us this past year and will continue to do so with your support. We’ve always understood the importance of calling out corruption, regardless of political affiliation.

We need your support in this difficult time. Every reader contribution, no matter the amount, makes a difference in allowing our newsroom to bring you the stories that matter, at a time when being informed is more important than ever. Invest with us.

Make a one-time contribution to Alternet All Access, or click here to become a subscriber. Thank you.

Click to donate by check.

DonateDonate by credit card
Donate by Paypal
{{ }}
@2022 - AlterNet Media Inc. All Rights Reserved. - "Poynter" fonts provided by