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The Link Between Deadly Weather and Global Warming Is Real -- and Conservatives Can't Just Wish It Away

Does extreme weather foretell the kind of climate that global warming is bringing us? Scientists say yes.

When a winter blizzard buried Washington, DC, in snow early last February, global warming denialists crowed that it "proved" global warming was hokum, even as forecasters were predicting the warmest Winter Olympics ever in Vancouver, which had just recorded its warmest January ever -- seven degrees Fahrenheit hotter than normal.  

"It's going to keep snowing in DC until Al Gore cries 'uncle,'" tweeted Sen. Jim DeMint, R-South Carolina, while Fox News did a segment featuring Gore's book, An Inconventient Truth, slowly being covered by falling snow. "Sixty-three percent of the country is now covered in snow and it's breaking Al Gore's heart because the snow is also burying his global warming theory, and outside our offices, his book," chortled Eric Bolling, sitting in for Neil Cavuto on his Feb 10 show.  

Climate scientists struggled to be heard with their message that yes, global warming could actually make such extreme snowstorms more common, at the same time that average global temperatures continue to rise.  

It was a counter-intuitive argument for the man or woman on the street, but this year, the shoe's on the other foot. It's the denialists suddenly arguing that people shouldn't jump to conclusions based on the weather right in front of them, after the most deadly spate of tornadoes since the 1930s swept across the southern United States the last week in April. Questions immediately arose about whether the intense spike in the number and intensity of tornadoes could be due to global warming. It's a natural question to ask, since most of us tend to think of climate in terms of what we experience directly ourselves―which is weather. But climate scientists said the same things this year that they said last year--repeatedly telling us that climate and weather are two different things.

"Climate is what you expect. Weather is what you get," said climate scientist Brenda Ekwurzel, of the Union of Concerned Scientists. The two are intimately related, but the relationship is statistical, not causal. That doesn't make it any less real, however. 

How Climate Scientists Think About Extreme Weather 

Global warming makes certain kinds of weather events increasing more likely, but it doesn't cause them, because no one thing ever does. Think of the seasons and air temperature as an example. Summer means the air is hotter, on average. Winter means the opposite. But that doesn't automatically make a summer midnight on an Alaskan mountaintop hotter than a winter mid-day in South Florida at the beach. There are multiple factors: Season, time of day, geographical location, altitude. Still, the fact that the season/air temperature relationship is not a causal relationship doesn't lead people to ignore it―especially when planning ahead. Winter clothes may differ from place to place, but they still regularly go on sale at roughly the same time. And the first cold snap generally reminds those who have put off shopping.  When it comes to global warming, extreme weather is like that cold snap: The important thing is not whether the coming of winter “caused” it. The important thing is that it's a harbinger of what's to come. 

What's more, any store that ignored the season/air temperature relationship―on the grounds that the two aren't causally related―would quickly go out of business. Something similar is happening with global warming; the costs of ignoring the climate/weather relationship are getting harder and harder on more and more bottom lines. No clothing store ever made a killing by waiting for absolute proof it was summer before putting swimsuits on sale. 

In order to understand what is or is not happening with tornadoes and global warming, we first need to understand the broader category of extreme weather events and how climate scientists think about them. Take the example of Russia's extraordinary heat wave and drought last summer, which set the stage for vast wildfires and resulted in tremendous wheat shortages, helping to drive up world food prices. As Adam Voiland of NASA's Earth Science News Team explained in an online article, “How warm was this summer?” this was a truly unprecedented event: 

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