Friday, August 31, 2018

Global Warming Can Make Extreme Weather Worse.  Now Scientists Can Say by How Much.

Researchers no longer hesitate to blame climate change for floods, fires and heat waves.  Here's how the science works.

A wildfire burns in Alvdalen, central Sweden, on July 26. (Credit: Maja Suslin / EPA file) Click to Enlarge.
When the heat waves, droughts, wildfires and deluges come — as they seem to with increasing regularity these days — the question inevitably arises:  Did climate change play a role?

The answer scientists gave for years was that greenhouse gases created by humans likely contributed to extreme weather, but it was hard to definitively tie the warming atmosphere to any single episode.

But that cautious approach, repeated in thousands of news reports for more than a decade, has been changing in recent months.  Now, scientists say that they will increasingly be able to link extreme weather events to human-caused global warming and to make such determinations quickly, sometimes within days.

So when a heat wave beset Northern Europe early this summer, bringing temperatures in Scandinavia into the 90s, a consortium of researchers operating under the name World Weather Attribution whipped together a series of computer simulations.  Within three days, the scientists issued a finding that the hot spell had been made at least twice as likely because of human-driven climate change.

In less frequent instances, scientists taking more time have reached even bolder conclusions — finding that some extreme events would not have happened at all in a pre-industrial era, when Earth's atmosphere had not been pumped full of carbon dioxide.

The trend promises to become even more pronounced in the coming years, because national weather agencies in countries like Germany and Australia, and the weather service for the European Union, expect to begin issuing regular findings on whether unusual weather events grew out of climate change.

“Usually scientists have been quiet or said only that ‘This is the kind of event that we would expect to happen more often,'" said Friederike Otto, deputy director of the Environmental Change Institute at Oxford University in England.  "But now we can, and will, be able to say more."

Read more at Global Warming Can Make Extreme Weather Worse.  Now Scientists Can Say by How Much.

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