PETER PARKS / AFP / Getty Images A record-busting heat wave has wilted Shanghai and other cities in Northeast Asia this summer

Northeast Asia is on fire. Yesterday temperatures in Shanghai hit an all-time high of 105.4ºF (40.8ºC), the hottest day in the coastal megacity since Chinese officials began keeping records some 140 years ago — during the Qing dynasty. On Aug. 12 the heat reached 105.8ºF (41ºC) in the southern Japanese city of Shimanto, the hottest temperature ever recorded in the country. Hundreds of people throughout South Korea have been hospitalized because of heatstroke, even as the government was forced to cut off air-conditioning in public buildings because of fears of a power shortage. As heat waves go, it’s a tsunami, similar to the brutally hot weather that singed Europe 10 years ago, which contributed to the deaths of over 30,000 people.

It’s also a glimpse of a blazingly hot future. We know that temperatures will generally rise as the globe warms thanks to increased greenhouse-gas emissions. (It’s right there in the name: global warming.) But as a new study published in Environmental Research Letters shows, the sort of scorching heat waves currently baking Northeast Asia are likely to become more frequent and more severe in the decades to come — and that’s going to happen no matter what we do about carbon emissions in the near future. There are some very uncomfortable summers on the horizon.

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The study, by researchers at the Potsdam Institute for Climate Impact Research (PIK) in Germany and the Complutense University of Madrid in Spain, used climate models to project how heat extremes would change over the next century. The scientists found that extreme heat waves like the one that baked much of the U.S. in 2012 — when the country had its warmest year on record — are projected to cover double the amount of land globally by 2020 and quadruple the territory by 2040. The most severe heat waves — so-called five-sigma events, because they would involve temperatures that are five standard deviations above the norm — would go from essentially nonexistent today to covering about 3% of the globe by 2040.

The researchers project that those heat waves will increase in frequency and intensity until 2040 even if the international community manages to reduce greenhouse-gas emissions — which, it should be pointed out, we’re not doing. (The carbon emissions we’ve already added to the atmosphere have baked in a certain amount of warming regardless of future climate policy.) But under a low-emissions scenario, the frequency of those nasty heat waves would likely stabilize in the second half of the century as the climate begins to heal itself. But if emissions just keep on rising, the heat waves will intensify — the three-sigma heat waves will cover 85% of the global land area by 2100, while five-sigma events will cover 60% of the globe by the end of the century.

Dim Coumou of the PIK put it this way:

In many regions, the coldest summer months by the end of the century will be hotter than the hottest experienced today — that’s what our calculations show for a scenario of unabated climate change. We would enter a new climatic regime.

It will be bad enough in places like Northeast Asia, which are already prone to hot summers. Imagine heat waves where temperatures top out above 115ºF (46.1ºC) or 120ºF (48.9ºC) in cities like Shanghai or Seoul. But tropical cities such as Mumbai or Jakarta could become hotter than human beings have any experience enduring. The optimist in me wants to think that we’ll find a way to adapt even to those temperatures — after all, thanks to the widespread use of air-conditioning, cities with painfully hot climates even before global warming, like Phoenix or Singapore, have thrived, taking in migrants from colder northern cities. But there has to be a limit — especially when you consider the wilting effect that extreme heat will have on crops. And we’re poised to burn right by it.

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