Rising temperatures from climate change rev the global water cycle.(2) Warming increases evaporation from the soil, plants and oceans, putting extra moisture into the air.(3),(4) Warm air is also able to retain more moisture than cold air, meaning there is more precipitation waiting to fall.(5),(6),(7)
When this precipitation does fall, it is more likely to be rain than snow since the temperature is warmer. When it rains, that extra moisture in the air makes it more likely that more rain will fall in shorter periods of higher intensity.(8),(9) This action increases the risk of flooding since the ground and sewer system cannot absorb rain quickly enough.(10),(11)
“Global warming encourages what would have been a normal rainstorm to become a real downpour and increases the risk of flooding.”
-Dr. Kevin Trenberth, National Center for Atmospheric Research(1)
How can rising temperatures cause more severe droughts and floods at the same time?
It might seem odd that rising temperatures could cause floods in some areas and drought in others, but that’s one of the unusual effects of climate change. Below is an illustration of how it happens.
Extreme precipitation becomes more common in the U.S.
Over the past 50 years, heavy precipitation increased across the continental United States as evaporation increases and the atmosphere holds more moisture. Since the atmosphere absorbs more water, heavy precipitation events are becoming more common and more intense.
Sources: Kenneth Kunkel, Cooperative Institute for Climate and Satellites, North Carolina State University, and NOAA NCDC
The heavy cost of heavy precipitation
Heavy precipitation events are becoming more common in the U.S., and have cost taxpayers billions of dollars in paying out insurance claims to private homeowners.(12) The government is the main provider of flood insurance in the country and the program is the second-largest government liability after Social Security.(13)
When not drained quickly enough, excessive rainfall can result in blackouts, overflowing sewage and disabled transportation systems.(14),(15),(16) Floods were also responsible for about 2,500 deaths over the past 30 years, making them one of the most dangerous weather-related hazards.(17) In June 2008, heavy rainfall caused record flooding on the Cedar River. Flooding displaced about 25,000 people and resulted in more than $10 billion in damages statewide.(18)
Most city infrastructure is designed for the largest storms in the area’s history.(19) Climate change makes storms more intense than historical averages and may overwhelm these systems. Adapting cities to handle more intense rainfall requires extensive planning and spending to improve under-designed infrastructure. Cities will need to invest in higher levees, improved drainage systems and other mitigation projects to better manage intense storms.(20)
- ABC News
- National Parks Service
- NOAA: Did You Know?
- ABC News
- NOAA: A Warming World Will Further Intensify Extreme Precipitation Events
- Science Daily
- Federal Emergency Management Agency
- NOAA: Heavy Downpours More Intense, Frequent in a Warmer World
- University of Wisconsin, Madison
- Insurance Journal
- NOAA: Insurance
- Fox News
- Chicago Tribune
- NOAA: Weather Fatalities
- NOAA: Iowa Floods
- Iowa Department of Transportation
- Government Accountability Office
- Precipitation Map – Climate Central