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Global warming evident in extreme US weather patterns: scientist

Scientists suggest recent extreme weather events, including wild fires, heat waves and storms, are evidence of global warming.

A US flag flies on a burnt car after fire ravaged 350 homes in a neighbourhood in Colorado Springs, Colorado last week.
A US flag flies on a burnt car after fire ravaged 350 homes in a neighbourhood in Colorado Springs, Colorado last week.

WASHINGTON // To glimpse some of the worst of global warming, scientists suggest looking at weather in the US in recent weeks.

Horrendous wildfires. Oppressive heat waves. Devastating droughts. Flooding from giant deluges. And a powerful freak wind storm called a derecho.

These are the extremes scientists predicted would come with climate change, although it is too early to say that this is the cause. Nor will they say global warming is the reason 3,215 daily high temperature records were set last month.

Scientifically linking individual weather events to climate change takes intensive study, and sometimes it is not caused by global warming. Weather is always variable. Freak things happen.

So far this year, more than 2.1 million acres have burnt in wildfires, more than 113 million people in the US were in areas under extreme heat advisories last Friday, two-thirds of the country is experiencing drought and, earlier in June, deluges hit Minnesota and Florida.

"This is what global warming looks like at the regional or personal level," said Jonathan Overpeck, professor of geosciences and atmospheric sciences at the University of Arizona. "The extra heat increases the odds of worse heat waves, droughts, storms and wildfire."

As recently as March, a special report on disasters by the Nobel Prize-winning Intergovernmental Panel on Climate Change warned of "unprecedented extreme weather and climate events".

Its lead author, Chris Field, of the Carnegie Institution and Stanford University, said on Monday: "It's really dramatic how many of the patterns that we've talked about as the expression of the extremes are hitting the US right now."

"What we're seeing really is a window into what global warming really looks like," said Michael Oppenheimer, a Princeton University geosciences and international affairs professor. "It looks like heat. It looks like fires. It looks like this kind of environmental disasters."

Mr Oppenheimer spoke on Thursday, before the East Coast temperatures above 38°C and before a derecho - an unusually strong, long-lived and large wind storm - blew through Chicago to Washington. The storm and its aftermath killed more than 20 people and left millions without electricity. Experts say it had energy readings five times that of normal thunderstorms.

Spring and winter in the US were the warmest on record and among the least snowy, setting the stage for the weather extremes to come, scientists say.

Since January 1, the US has set more than 40,000 hot temperature records, but fewer than 6,000 cold temperature records, according to the National Oceanic and Atmospheric Administration.

While at least 15 climate scientists said this long, hot, US summer is consistent with what is to be expected in global warming, history is full of such extremes, said John Christy, of the University of Alabama, who said: "The guilty party in my view is Mother Nature."

But most climate scientists, such as Jerry Meehl, of the National Centre for Atmospheric Research, disagree. "This is what global warming is like, and we'll see more of this as we go into the future," he said.