Global 'weirdness' seen in summer's extreme weather events - USA TODAY

By Dan Vergano, USA TODAY

Updated

A melting Greenland glacier, summer heat waves, a devastating "derecho," drought: Is it all part of global warming or "global weirdness"?

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On July 2012, a massive ice island broke free of the Petermann Glacier in northwestern Greenland.

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A plague of extreme weather events, from Greenland briefly thawing to the derecho thunderstorms that knocked out power for millions across the Mid-Atlantic and parts of the Midwest has struck this summer. Above all, an exceptional drought has marked roughly 50% of all U.S. counties nationwide as federal disaster areas. That's on top of last year, which saw record U.S. tornadoes, floods and a drought that tortured Texas and Oklahoma.

Has global warming arrived not with a bang or a whimper, but with wild weather?

It's starting to look that way, suggests science writer Michael Lemonick, co-author of this year's Global Weirdness: Severe Storms, Deadly Heat Waves, Relentless Drought, Rising Seas and the Weather of the Future. "In retrospect, we'll look back and say we were starting to make changes to climate back then," Lemonick says. "But you can only say that in retrospect."

Reviewed by a panel of climate scientists, Global Weirdness looks at global warming and finds temperatures, heat waves and sea levels all increasing as predicted. Many extreme events, such as tornadoes or floods, look to be only suggestive of the results of a warming climate.

Greenland's July thaw provides an example of extreme weather, where satellite data showed that over four days about 97% of the massive ice sheet surface covering the island was melting, due to a heat wave. The news followed a space agency report that a 30-mile-long slab of Greenland's Petermann glacier had broken off and was headed to sea.

Greenland holds enough ice that if it melted instantly â€" which no one is predicting â€" sea levels worldwide would rise about 20 feet, explaining the interest in its weather.

In reality, such surface thaws have happened before: A melt in 1889, judging by ice cores, and much of the four-day melt this summer refroze once the heat wave passed, according to The Arctic Institute, a Washington, D.C.-based think tank. And a May Science journal report found that Greenland's glaciers overall slid into the sea less rapidly over the past decade, easing sea-level-rise worries.

Atmospheric scientist Clifford Mass of the University of Washington in Seattle suggests that the year's freak weather is just that, not a sign of anything. "Extremes are where we have the most uncertainty," he says.

While the U.S. is enduring its warmest year on record, the year has been only the 11th-warmest on record worldwide, at least so far, according to the National Oceanic and Atmospheric Administration.

Strong evidence suggests that global warming is occurring, regardless, and most likely raising average surface temperatures worldwide about 1.4 degrees Fahrenheit over the past century, according to the U.S. National Academy of Sciences. In 2011, the academy concluded that "climate change is occurring," driven by burning fossil fuels that add greenhouse gasses to the atmosphere.

"It's clear that when we look at the consequences of climate change, that it's in severe weather where we are going to see effects," says climate scientist Don Wuebbles of the University of Illinois at Urbana-Champaign.

Wuebbles grew up on a farm in southern Illinois and has spent much of the summer answering drought questions from farmers. "This summer fits the general pattern," he says. "I suspect people are starting to see that."

But once you get past warmer temperatures, the evidence for global warming playing a role in floods, droughts or other extreme weather disasters becomes extremely thin, Mass says.

Some climate projections suggest that climate change might even lessen extremes, he adds, more often clearing the "blocked" weather patterns behind the Midwestern drought. "The trouble is people are looking for simple answers and the situation isn't simple," Mass says.

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