Extreme temperatures, whether too hot or too cold, carry a colossal health and human cost. That is the finding of an analysis authored by dozens of scientists.
Since the first cases were identified in Wuhan in January 2020, almost four million people have lost their lives to Covid-19. To be precise, according to the World Health Organisation, 3,992,680. A gravely serious toll that, rightly, set off an unprecedented effort to defeat the virus. Yet it is rarely reflected upon that extreme temperatures, which have now become the norm due to global warming, also carry a cost in human lives. A cost that a recent study estimates at more than 5 million deaths a year worldwide.
Dozens of scientists analysed temperature and mortality rate data from 750 locations spread across 43 different countries, over a time span running from 2000 to 2019. The outcome of this monumental work was published in The Lancet Planetary Health. At the global level, extreme temperatures are associated with more than 5 million deaths a year, equivalent to 9.43 per cent of total deaths. To use another measure, for every 100,000 people there are 74 more deaths than the norm.
So far, these extreme temperatures have been predominantly too low (nearly 4.6 million cases) and, less frequently, too high (489,000 cases). Over the coming years, however, this ratio will change considerably and heat will have a far greater impact. Indeed, over the period studied, the average temperature rose at a rate of 0.26 degrees Celsius per decade.
Right now, the United States and Canada are grappling with a heat dome that has been accompanied by hundreds of sudden deaths (486 in British Columbia, 107 in Oregon, 30 in the state of Washington). A phenomenon that, without climate change, would have been "virtually impossible". So says a study authored by 27 scientists, still awaiting peer review.
Had the exact same conditions occurred at the start of the industrial era, temperatures would have been considerably lower (fully 2 degrees Celsius less). In a hypothetical future in which global warming breaks through the dreaded 2-degree threshold — something that is unfortunately very likely, according to the United Nations Environment Programme — heatwaves of this kind will no longer occur once every millennium but rather every 5 to 10 years. And the mercury will climb a further degree.