Heat waves have killed thousands this year​​​​​​​. Experts say the worst could be yet to come

The ongoing heat wave gripping the Northern Hemisphere hasn't just triggered triple-digit temperatures, but also a sizeable death toll. From India to Saudi Arabia to Massachusetts, many regions across the globe have buckled under extreme heat — but while such phenomena is normal during the summer months, the degree to which things are cooking is not.

Unsurprisingly, climate change is a major culprit in this unfolding crisis and experts agree that it will get worse.

On Tuesday, AFP reported 550 people had died from heat-related causes during Hajj, an annual Islamic pilgrimage to Mecca. By Thursday, the death toll had nearly doubled to 1,081 across at least 10 countries, with the principal reasons for death being dehydration, heat stroke, high blood pressure and other heat-related issues. One Egyptian man, according to the Associated Press, broke down in tears when learning that his mother was among the dead, and then called his travel agent in distress.

“He left her to die,” he shouted, referring to the agent, while those nearby tried to comfort him.

Meanwhile, more than 100 people have died in India from extreme heat in the last three-and-a-half months, with more than 40,000 cases of heat stroke being reported. One of India's largest hospitals in Delhi has created a first-ever heat stroke emergency room, with one doctor reporting that "in my 13 years of working here, I don’t remember signing a death certificate for heat stroke. This year, I’ve signed several."

And in the northeastern United States, more than 135 million people are under a heat advisory, with the holiday weather breaking temperature records both there and in the midwest. Europe is also under the grips of an unprecedented heat wave, with at least five people dying in Greece so far, as well as a heat dome that killed at least 61 in Mexico earlier this month.

"I am 100% certain that worsening heat waves across Earth are due to global heating caused primarily by burning fossil fuels," said Dr. Peter Kalmus, a NASA climate scientist, who emphasized his opinions are his own. "We see intensifying extreme heat in all observational datasets and model hindcasts."

Kalmus told Salon that quantified attribution studies — ones that, importantly, use models both with and without the presence of accumulated anthropogenic greenhouse gases in the atmosphere — show it is probable that the recent heat waves follow a pattern based on fossil-fueled global heating. The question becomes how much is climate change at fault and how much is part of El Niño and regular old summer?

Dr. Michael E. Mann, a climatologist at the University of Pennsylvania, told Salon "We have to be careful with the framing."

"Might there have been a heat wave like this without the effect of human-caused warming from carbon pollution? Perhaps." Mann said. Yet he added, "Would it have been as intense and persistent as this one? Almost certainly not."

"There's always a chance that we could have temporarily experienced extreme heat in this spatiotemporal pattern even without global heating, even if that chance is nearly zero," said Kalmus. "But when you look at intensifying extreme heat trends overall, it's 100% certain that this is caused by global heating at this point."

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Dr. Kevin Trenberth, a distinguished scholar at the National Center for Atmospheric Research who has published more than 600 articles on climatology, said that it would be simplistic to frame the current heat waves as being caused entirely by climate change.

"Climate change does not cause heat waves as such," said Trenberth. "The heat waves and their intensity and location are related mostly to the weather patterns, that even now are dominated by natural variability. What climate change does is exacerbate certain extremes. In particular in hot summer weather human-induced climate change makes the consequences much worse."

With thousands dying across the world, one major factor determining survival rates is income. In Saudi Arabia, for example, tens of thousands of low-income Muslims who cannot afford official permits take their pilgrimage to Mecca by using irregular channels and therefore lack access to the air conditioned spaces available for the 1.8 million people who are authorized to undertake the pilgrimage. Yet even people in more affluent countries are at risk if they stay outside too long.

"Of course, we need to take all of the steps we can to minimize the public health risk from extreme heat, and that requires a mobilization of resources and collaboration between policymakers, emergency managers and other stakeholders," Mann said. "But the only way we can prevent this from getting worse is to address the problem at its source; the ongoing warming of the planet from fossil fuel burning and other activities that generate carbon pollution."

Barring major changes in human behavior, climate change is expected to only get worse. In a recent study of hundreds of climate scientists by The Guardian, nearly 80 percent of the experts foresee Earth's temperature rising at least 2.5º C (4.5º F) above pre-industrial levels; almost half believe the temperature will rise at least 3º C (5.4º F) above that level. Only 6% thought the limit of 1.5º C (2.7º F) — the one agreed upon at the Paris climate accord, and widely acknowledged as being a major threshold before global catastrophe — is even attainable.

Regardless of whether Earth can avoid the more apocalyptic scenarios, however, experts agree that increasingly severe heat waves will exist in the foreseeable future.

"We can expect extreme heat, including deadly heat, to continue intensifying so long as the fossil fuel industry continues to exist, as they are the primary cause of global heating," Kalmus said. Like Mann, he said that humans need to rapidly transition away from fossil fuels, humans will soon experience heat waves that kill millions within a few days.

"If we continue burning fossil fuels despite such deadly warnings from the overheating Earth system, this death toll will continue to mount — and at some point the first 10-million-death heat wave will occur," Kalmus warned. "There's no good way to prepare for such deadly heat — air conditioning can go out in a blackout, and blackouts are more likely during heat waves — so the best preparation at this point is to minimize how hot things get by doing everything you can to end the fossil fuel industry as quickly as possible."