Climate change increases the odds of worsening drought in many parts of the United States and the world in the decades ahead. Regions such as the U.S. Southwest will see increased heat, changing rainfall patterns and less snowpack contributing to drought conditions. Even in regions that may not see changes in precipitation, warmer temperatures can increase water demands and evaporation, putting greater stress on water supplies.
Recent U.S. droughts have been the most expansive in decades. In 2011, Texas experienced its driest 12 months ever. At the peak of the 2012 drought, an astounding 81 percent of the contiguous United States was under at least abnormally dry conditions.
Globally, drought struck several major breadbasket regions simultaneously in 2012, adding to food price instability. In countries already facing food insecurity, cost spikes can lead to social unrest, migration, and famine.
Estimates of future changes in seasonal or annual precipitation in a particular location are less certain than estimates of future warming. However, at the global scale, scientists are confident that relatively wet places such as the tropics and the high latitudes will get wetter, while relatively dry places in the subtropics (where most of the world’s deserts are located) will become drier.
Threats Posed by Drought
Warmer temperatures can amplify the impacts of drought. Increased temperatures enhance evaporation from soils, making periodic droughts worse than they would be under cooler conditions. Droughts can persist through a “positive feedback,” where very dry soils and diminished plant cover can further suppress rainfall in an already dry area.
The United States is historically susceptible to drought. Paleoclimate studies show major droughts in the distant past, while some more recent dry periods are still within living memory, such as the Dust Bowl of the 1930s or the drought of the 1950s. These historic examples serve as guideposts to highlight our vulnerabilities to drought as we move into a warmer and, in some places, drier future.
Severe drought can affect:
- Agriculture: Droughts affect livestock and crops, including cornerstone commodities like corn, soybeans, and wheat. At the height of the 2012 drought, the U.S. Department of Agriculture declared a natural disaster over 2,245 counties, 71 percent of the United States.
- Transportation: Droughts can affect water levels on rivers of commerce like the Mississippi. Transport barges need at least nine feet of water, and to maintain this level, the U.S. Army Corps of Engineers had to blast, dredge, and clear obstructions on a key stretch of the Mississippi in 2013.
- Wildfires: [link to wildfires page] Drought conditions and record heat have fueled damaging and sometimes deadly wildfires in the U.S. West. Millions of forested acres and thousands of homes have been lost over the past decade due to fires thriving in dry, stressed forests and the proximity of communities to fire-prone forests.
- Energy: Droughts can raise concerns about the reliability of electricity production from plants that require cooling water to maintain safe operations. Hydroelectric power may also become unavailable during droughts. When heat waves coincide with droughts, electricity demands can grow, compounding stress on the grid.
How to Build Resilience
- Governments and businesses must identify their drought vulnerabilities and improve their resilience. Actions like using water more efficiently and developing more drought-resistant crops will help prepare for both future droughts and climate change.
- Other actions that improve resilience to other stressors, like deploying green infrastructure for stormwater management or increasing energy efficiency in buildings (thereby using less water-cooled power), can improve resilience to drought as a co-benefit.
These steps will be most effective if they are combined with reductions in greenhouse gases that can minimize the ultimate magnitude of climate change.