Is global warming causing more floods?
Because flood risk is the result of both environmental and societal factors, it is difficult to single out the impact of climate variations. According to the United Nations Intergovernmental Panel on Climate Change (IPCC), the average global temperature at the surface increased just over 1.0 degree Fahrenheit in the 20th century. At the same time, according to NOAA, there has been a steady increase in the area of the United States affected by extreme precipitation events (more than two inches of rain in one day, or the equivalent in snow). However, flood reports have not increased uniformly across the country. For instance, streamflows in the Colorado River basin have decreased over the past 60 years. Any alteration of global climate can bring either an increase or decrease in precipitation or flood events at a given location. Current computer models of climate are unable to project local variations with certainty. For the most recent global and national scenarios, see the Web sites fo
