The Winds of Change

| 7/8/2011 5:10:15 PM

Tags: tornadoes, oceans, global warming, climate change, Paul Epstein, environment, The Atlantic, David Doody,

tornado-weather-serviceToday kicks off a four-part series on climate change at The Atlantic. Part one comes from Paul R. Epstein, co-author of the book Changing Planet, Changing Health. Epstein tells us just how changing temperatures in the oceans can lead to more severe weather in the middle of the U.S., like the calamitous tornado earlier this year in Joplin, Missouri.

So global warming is thus causing climate change, including altered weather patterns, and the engine of change is the heat building up deep inside the world's oceans. Water is warming, ice is melting, and water vapor is rising. How does this help explain tornadoes? …

It's all about contrasts and gradients. Warmer temperatures over land surfaces create low-pressure systems (since hot air rises, creating "lows"), while cold fronts from the north come with high pressures. Weather "flows downhill," as it were—from highs to lows. When temperature and pressure gradients between highs and lows increase (as they do naturally in spring), the clash can twist to form tornadoes. The greater the contrasts, the greater the force of the twisters.

This spring, especially warm and moisture-laden air from the Gulf of Mexico met up with especially cold fronts from the north, driven by melting Arctic and Greenland ice.

Epstein cautions against assuming that any of this means a predictable increase in severe weather. In fact, the unpredictability is the point here. There may be years when severe flooding and tornadoes seem much milder than the previous year. “But,” Epstein writes, “it is clear that changing atmospheric and oceanic conditions underlie the changing patterns of weather—and that the stage is set for more severe storms, including even more punishing tornadoes.”

Keep an eye out for the other three parts in this series from The Atlantic.

Source: The Atlantic