Extreme weather events on the rise, says climate group

Posted by Emma Woollacott

Climate change is loading the dice in favor of extreme weather events like Huricane Irene, a new report suggests.

Heat waves, torrential rain and droughts are likely to be more frequent and more severe, says Climate Communication in a report which summarizes recent peer-reviewed scientific literature.

"Small global average temperature rises lead to big changes in extreme weather,” says Jerry Meehl, senior scientist at the National Center for Atmospheric Research (NCAR).

"As a result, we’re now seeing extreme heat events that were once rare occurring more frequently. Continued emissions of heat-trapping gases will lead to even more frequent and intense heat extremes."

Warmer air holds more water vapor, and when a storm system moves through, the extra water dumps out as heavy rain. Between downpours, there are longer periods without rain, bringing a cycle
of droughts and floods.

"Sustained heavy precipitation leads to the types of floods we’ve seen in recent years in Pakistan, Australia, and the Mississippi," says NCAR's Kevin Trenberth.

At the same time, dry areas are becoming drier, due to lack of precipitation coupled with increased evaporation that is associated with higher temperatures. Across the globe, says Climate Communication, very dry areas have doubled in size since the 1970s.

Meanwhile, the intensity of Atlantic hurricanes has increased, as warmer oceans drive stronger storms, and this pattern is
expected to continue in future decades.

"By the end of this century, climate models suggest we may see an 80 percent increase in the number of Category 4 and 5 hurricanes,” says Jeff Masters, director of meteorology at Weather Underground.