Are climate change deaths increasing? Here's why experts expect humans to adapt to our heating world

Climate change poses a major existential threat to humanity, meaning billions of people could die as the planet becomes too hot and unstable to live. Case in point, the rash of record-breaking heat waves that have dominated this summer thanks to unprecedented temperatures have caused mass casualty events. This includes more than 100 people in India dying of extreme heat in the last three-and-a-half months, to more than 60 people who died in a Mexican heat dome, to nine confirmed deaths in Las Vegas during its recent heat wave, to more than 550 people who died in Saudi Arabia while performing an important Islamic religious journey known as Hajj.

While summer heat waves have pretty much always been a thing, it's clear that human activity is making them hotter and deadlier. emit greenhouse gases like carbon dioxide, methane, nitrous oxide, fluorinated gases and water vapor into the atmosphere, they continue overheating the planet, pushing Earth's life forms to the limits of their thresholds for survival.

"If we don’t adapt, heat wave mortality will increase sharply," Michael Wehner, a senior scientist in the Computational Research Division at the Lawrence Berkeley National Laboratory, told Salon. "Fortunately, humans are an adaptable species and some of that is already happening in efforts to increase awareness of heat wave dangers."

Yet this can only accomplish so much, as the high temperatures are inherently dangerous "and people will die from them as we won’t be able to adapt completely," Wehner said. "Those at risk — the very poor, the very old, the very young the very ill and those who work outdoors — must be very careful during these unprecedented heat waves."

Martin Siegert, a glaciology professor at the University of Exeter and former co-director of Imperial College London's Grantham Institute for Climate Change, elaborated on exactly why both heat waves and the other major extreme summer weather event linked to climate change — storms — are so dangerous.

"For heat, when temperatures get too hot for the human body, between 40º-50º C the body needs more energy to cool itself - and stops functioning properly," Siegert said. "As temperatures push above that, or consistently at it, then we expect many deaths. Perhaps in huge numbers in places where air conditioning and shelter is absent. For storms, the situation is different — here risk to life is in flying debris, floods and poor decisions when risks are high — such as driving through floods, or under flooded underpasses."

This is not the limit of how global heating will endanger people, Siegert said; in a seeming paradox, the warming phenomenon can actually lead to "some colder conditions as the atmosphere becomes more energetic — and this too is a killer."

Patrick Brown, a visiting research professor at San Jose State University's Wildlife Interdisciplinary Research Center, disagrees with those who say climate change is causing increased mortality, citing the IPCC Sixth Assessment Report while doing so.

"Heat deaths are declining over time, despite warming, because societies are becoming less sensitive to temperature faster than temperatures are rising," Brown said. "Here is how the IPCC puts it: 'Heat-attributable mortality fractions have declined over time in most countries owing to general improvements in health care systems, increasing prevalence of residential air conditioning, and behavioural changes. These factors, which determine the susceptibility of the population to heat, have predominated over the influence of temperature change.'"

Some have argued that fossil fuel companies, being directly responsible for these deadly temperatures, should be charged with homicide. The consumer advocacy nonprofit Public Citizen released a model prosecution memo last month laying out a case to hold major fossil fuel companies criminally accountable for deaths from climate disasters as well as other climate-related harms in Maricopa County, Arizona.

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However, some experts believe climate-related deaths could peak as humans adapt. Indeed, because of humanity's technological advances, Brown expects death rates in general to go down in the foreseeable future.

"I don't expect death tolls to increase but instead continue to decrease because crop yields and calories available per person have increased," Brown said. "Death rates from malnutrition and famines have decreased; the share of the population with access to safe drinking water has increased; the rates of climate-influenced diseases like malaria and diarrheal disease have decreased; death rates from natural disasters have decreased; death rates from non-optimal temperatures (hot and cold) have decreased; and the fraction of people in extreme poverty has plummeted."

Siegert offered a contrasting perspective, anticipating that in addition to increased deaths caused by heat waves and super storms, people should also expect heightened mortality rates because of flooding, whether due to sea level rise or weather events.

"The largest impacts from hurricanes are flood-related," Siegert said. "Many people drown in these events both from saltwater floods driven by storm surge and by freshwater flooding driven by copious amounts of rainfall. Many of these deaths are avoidable if people would heed evacuation notices."

Siegert added, "There is some concern about increases in the range of infectious tropical diseases but that is not as well understood as heat wave risk."

By contrast, Brown told Salon that finds it "interesting that many people are under the impression that we should expect to see large increases in deaths from climate change-related shifts in natural disasters when the evidence for this is so weak. I think this speaks to the information environment that we live in being potentially quite divorced from reality."