In case your day wasn't already enough of a bummer, why not a quick refresher on some of the impending effects of climate change?
Sleep loss due to higher night temperatures? Check. Dehydration as a deadly disease? Check. Worsening airplane turbulence? Check. Increased stress, depression, and anxiety among people thinking about climate change? Check.
Now you can add killing heat to that list. A new study, published in Nature Climate Change, models just how many people may be affected by rising heat. Today, killer temperatures affect about 30 percent of the global population at least 20 days out of the year. If greenhouse gas emissions continue to rise, by 2100 that number could be 74 percent. Even if we drastically reduce emissions, by 2100 nearly half the world's population would be exposed to deadly high temperatures at least 20 days out of the year. That means more deaths, especially among the elderly.
To create their models, researchers first had to understand the conditions that turn high temperatures deadly. The hackneyed saying "it's not the heat, it's the humidity" turned out to be true. Looking at earlier studies, published between 1980 and 2014, they identified the threshold at which the combination of average daily temperature and average daily humidity becomes lethal. (With higher humidity, your body has a harder time cooling itself by sweating; your core gets hotter and your organs can malfunction.)
The researchers built climate models under three different scenarios: no change in emissions, a moderate decrease, and a strong decrease. The number of deadly days is already higher than in the past—no surprise there, as 2016 was the hottest year on record, and the third consecutive record-breaking year. And the models predict it's inevitable that more people will face killer heat, even if mitigate our carbon emissions. (Just a reminder here that President Trump has pulled the US from the Paris climate accord.)
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People in the tropics will be hardest hit, according to the study. "Unfortunately, many of the countries that could be hardest hit by these changes are also some of the poorest, whose citizens may have less access to air conditioning or hospital facilities during these times of high heat stress," Iain Caldwell, one of the study's authors, told ResearchGate.
Caldwell also suggests that while, yes, we desperately need global policy to address climate change, we can still make personal decisions to limit our carbon footprints. Limiting the amount you drive a car may sound like a meager contribution, until enough people do it, and the scales start tipping. If nothing else, taking climate change personally—while not what's beyond your control stress you out—might offer small but necessary consolation. It might help you sleep, even as the nights get hotter.
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