Our research group wrote an opinion article that was published today in the New York Times. It summarizes Ethan Coffel's recent study showing that heat-humidity combinations so extreme that even constant sweat won't be able to sufficiently cool us down will become a reality and then a regularity by 2080 in parts of the tropics and subtropics, many of them densely populated and all of them having contributed relatively little to cumulative greenhouse-gas emissions. The rest of the world will also see sharp increases in extreme humid heat, and the resulting heat stress. Although these projections are for the late 21st century and RCP8.5, what's considered the 'worst-case' trajectory (with warming of 3.0-4.5 deg C since the 19th century), that's exactly the trajectory that the world has been on ever since the first IPCC Assessment Report in 1990. Glimmers of meaningful changes are happening, but there's still a long way to go before global emissions begin to decelerate -- and then level out -- and then drop. All the while, concentrations of greenhouse gases in the atmosphere will continue to rise.
In a long-term sense, then, the just-released IPCC report on climate changes for 1.5 deg C of warming vs 2.0 deg C is good for awareness but mostly an exercise in rearranging the deck chairs on the Titanic. In all likelihood, we'll blow by both of those targets within 30 years. Among many other things, that means there'll be a continuing need for evaluating the effects of this ever-increasing heat on health, the economy (e.g. agriculture, natural resources, tourism), and ecosystems. It would be great if this article, with its focus on awareness of the risks and its faint policy recommendations, were the last of its kind, but many more such articles will probably be necessary. Being the bearer of bad news is not a pleasure so much as a service. As a climate scientist, I got into this business because I enjoy understanding the intricate patterns, and in the absence of anthropogenic climate change there would still be plenty to study -- understanding natural variability, advancing high-resolution modeling, working on seamlessly merging climate and weather prediction. That's the positive message I try to convey when discussing my work, but that's not to make light of the very real risks that the most hard-edged aspects of climate change, such as extreme humid heat, will pose to lives, property, and livelihoods around the world.
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