2018's Hemispheric Heat Wave Wasn't Possible Without Climate Change, Scientists Say

https://insideclimatenews.org/news/11042019/2018-heat-wave-climate-change-attribution-northern-hemisphere-extreme-weather-record

By Bob Berwyn, InsideClimate News
Apr 12, 2019

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A study presented this week at a scientific conference in Vienna now shows that last summer's extreme heat was an "unprecedented" hemispheric event that would not have happened without heat-trapping greenhouse gas pollution, the researchers said, and that it lasted longer and was more widespread across the Northern Hemisphere than previously realized.

All summers will be like last year if the world warms 2 degrees Celsius above pre-industrial levels, said the study's lead author Martha Vogel, an extreme-temperature researcher with ETH Zürich Institute for Atmospheric and Climate Science. Even with 1.5 degrees Celsius warming, 25 percent of the Northern Hemisphere will experience a summer as hot as the summer of 2018 two out of every three years, she said.

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From May to July, the heat waves affected 22 percent of the agricultural land and populated areas in the mid-latitudes of the Northern Hemisphere, from Canada and the United States to Russia, Japan and South Korea, killing hundreds of people, devastating crops and curtailing power production. On an average day during those heat waves, 5.2 million square kilometers (about 2 million square miles) were affected by extreme heat, Vogel said. At its peak extent in July, the affected area was twice as big.

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The growing likelihood of widespread heat waves raises concerns about food security, as well as human health, and the impacts can ripple well beyond the affected countries, said co-author Sonia Seneviratne, a climate researcher with ETH Zürich.

The 2018 heat wave caused total losses of some crops in Germany and Austria, and spurred large-scale outbreaks of tree-killing bugs.

In the Scandinavian Arctic, temperatures soared to above 30 degrees Celsius (86 degrees Fahrenheit) for the first time on record, leading to unusual fires in the boreal forests of Sweden. Across Europe, river flows reached record lows in late summer and autumn, hampering commercial shipping and power generators that rely on rivers for cooling.

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