It’s been difficult for average citizens to imagine what global warming means for them. After all, a few degrees of increase in the global mean temperature doesn’t seem too bad. But one consequence that has already been documented is an increase in intense downpours with longer dry periods in between. A recent report  from the U.S. Global Change Research Program said,
“Changes in the geographical distribution of droughts and flooding have been complex. In some regions, there have been increases in the occurrences of both droughts and floods.” (p. 18) “The widespread trend toward more heavy downpours is expected to continue, with precipitation becoming less frequent but more intense.” (p. 24)
The historic drought that gripped the Southeast for the better part of two years and the severe flooding  that hit the same region last week illustrate this pattern all too graphically.
|“Today on the banks of a withering Lake Lanier, Governor Sonny Perdue announced the designation of 85 counties in Georgia under a state of emergency due to Georgia's prolonged drought. Governor Perdue also announced that he has requested President Bush to declare a major disaster area in Georgia.”|
U.S. States News, October 20, 2007
"I am confident President Obama will recognize the extensive damage these floods have caused on such a large metro area," Perdue said. This request for disaster funding is essential for the recovery and rebuilding process to begin for these Georgians, local governments and businesses."
Georgia Governor Sonny Perdue quoted in Atlanta Business Chronicle, September 22, 2009
In October of 2007 virtually the entire Southeast was locked in a devastating drought that destroyed crops, promoted forest fires, and ignited a nasty feud among several states over access to water sources that extended to the White House  and the courts . The reservoirs that supply the thirsty Atlanta metro region in northern Georgia were at their lowest levels in history. Sonny Perdue, Georgia’s governor, declared a state of emergency  in 85 counties and asked President Bush to follow suit with a federal disaster declaration so that Georgia could gain access to federal disaster relief funds.
|Source: U.S. Drought Monitor |
Fast forward barely two years—Last week the Southeast was inundated by “epic floods ” with the Atlanta area getting the brunt of the impacts. In rapid response mode, Gov. Perdue once again declared a state of emergency  and asked  President Obama for a federal emergency declaration.
|Source: NASA Earth Observatory |
Meanwhile, the same day Governor Perdue asked President Obama to declare a federal emergency in northern Georgia, the USDA announced that 50 of California’s 58 counties had been declared  a natural disaster area because the historic drought that has gripping that state has devastated crop production and farmers were in need of financial assistance. Texas  farmers are experiencing a similar drought disaster this year. And don’t forget the dramatic increase in western wildfires  and the two 500-year floods  that struck the Midwest just 15 years apart in 1993 and 2008.
Elsewhere in the world, the Philippines  just experienced its worst flooding in decades, courtesy of Tropical Storm Ketsana, while Guatemala  and east Africa  suffer from the worst droughts they have seen in decades, raising concerns that endemic hunger will return to those developing regions.
Climate scientists are very cautious about blaming individual events  on climate change, and poorly planned urban development and population growth  clearly exacerbated the effects of the recent Southeast drought. But whether or not Georgia’s weather rollercoaster ride is related to climate change, it offers a glimpse of what scientists have been warning us about. They have documented an increasing global trend in extreme weather events over the past 50 years and have linked  this overall trend to human-induced global warming.
So as you consider all of the record-breaking weather events happening around the world, you can be confident that, yes, they are more frequent than they used to be and will be even more frequent in the future because of global warming. The higher we allow atmospheric greenhouse gas concentrations to grow, the wilder we can expect the rollercoaster ride to get.
Jay Gulledge is a Senior Scientist and Program Manager for Science & Impacts