Global Warming increasing as greenhouse gases grow

In this year alone massive blizzards have struck the U.S. Northeast, tornadoes have ripped through the nation, mighty rivers like the Mississippi and Missouri have flowed over their banks, and floodwaters have covered huge swaths of Australia as well as displaced more than five million people in China and devastated Colombia. And this year's natural disasters follow on the heels of a staggering litany of extreme weather in 2010, from record floods in Nashville, Tenn., and Pakistan, to Russia's crippling heat wave.

These patterns have caught the attention of scientists at the National Climatic Data Center in Asheville, N.C., part of the National Oceanic and Atmospheric Administration (NOAA). They've been following the recent deluges' stunning radar pictures and growing rainfall totals with concern and intense interest. Normally, floods of the magnitude now being seen in North Dakota and elsewhere around the world are expected to happen only once in 100 years. But one of the predictions of climate change models is that extreme weather—floods, heat waves, droughts, even blizzards—will become far more common.

So are the floods and spate of other recent extreme events also examples of predictions turned into cold, hard reality?

Increasingly, the answer is yes. Scientists used to say, cautiously, that extreme weather events were "consistent" with the predictions of climate change. No more. "Now we can make the statement that particular events would not have happened the same way without global warming," says Kevin Trenberth, head of climate analysis at the National Center for Atmospheric Research (NCAR) in Boulder, Colo.

That's a profound change—the difference between predicting something and actually seeing it happen. The reason is simple: The signal of climate change is emerging from the "noise"—the huge amount of natural variability in weather.

State-of-the-art climate models, as used in the assessments of the Intergovernmental Panel for Climate Change, could be giving a false sense of security in terms of upcoming abrupt change, suggests a Commentary by a University of Bristol scientist published online this week in Nature Geoscience.

Professor Paul Valdes of the School of Earth Sciences, discusses four examples of abrupt climate change spanning the past 55 million years that have been reconstructed from palaeoclimate data.

In two of the cases, complex climate models used in the assessments of future climate change did not adequately simulate the conditions before the onset of change.

Professor Valdes concludes that state-of-the-art climate models may be systematically underestimating the potential for sudden climate change.