The United States is historically susceptible to drought. In the West, drought has continued and intensified in 2021, and has been exacerbated in the Pacific Northwest by record heat. Nationwide, conditions reached their peak in December 2020, when the greatest extent of land since 2012 was under extreme drought conditions. The intense drought and heat combined to wither vegetation, intensifying Western wildfires that burned record acreage. 2020 saw widespread, prolonged drought that was exacerbated by heat waves in more than a dozen Western and Central states. At the peak of the 2012 drought, the most extensive drought since the 1930s, an astounding 81 percent of the contiguous United States was under at least abnormally dry conditions.Ĭalifornia experienced a particularly drawn-out drought from December 2011 to March 2019, broken in part by the wettest winter in the United States. droughts have been the most expansive in decades. In some areas, droughts can persist through a vicious cycle, in which very dry soils and diminished plant cover absorb more solar radiation and heat up, encouraging the formation of high pressure systems that further suppress rainfall, leading an already dry area to become even drier.However, at the global scale, scientists are confident that relatively wet places, such as the tropics and higher latitudes, will get wetter, while relatively dry places in the subtropics (where most of the world’s deserts are located) will become drier. Estimates of future changes in seasonal or annual precipitation in a particular location are less certain than estimates of future warming, and are active areas of research.

For example, the Southwestern United States has already seen a decrease in annual precipitation since the beginning of the 20 th century, and that trend is expected to continue.Climate change is making certain regions drier.This creates the need for expanded water storage during drought years and increased risk of flooding and dam failure during periods of extreme precipitation. Some climate models find that warming increases precipitation variability, meaning there will be more periods of both extreme precipitation and drought.Because snow acts as a reflective surface, decreasing snow area also increases surface temperatures, further exacerbating drought. Likewise, certain ecosystems also depend on snowmelt, which supplies cold water for species like salmon. This is because many water management systems rely on spring snowpack melt. Decreased snowpack can be a problem, even if the total annual precipitation remains the same.Warmer winter temperatures are causing less precipitation to fall as snow in the Northern Hemisphere, including in key regions like the Sierra Nevada of California.Climate change is also altering the timing of water availability.This makes periods with low precipitation drier than they would be in cooler conditions. Warmer temperatures enhance evaporation, which reduces surface water and dries out soils and vegetation.

How climate change contributes to drought:

Southwest, where droughts are expected to get more frequent, intense, and longer lasting, are at particular risk. Drought and Climate ChangeĬlimate change increases the odds of worsening drought in many parts of the United States and the world. Adjusted precipitation data incorporate adjustments to the original station data to account for discontinuities from non-climatic factors, such as instrument changes or station relocation.A drought is “a deficiency of precipitation over an extended period of time (usually a season or more), resulting in a water shortage.” Indicators of drought include precipitation, temperature, streamflow, ground and reservoir water levels, soil moisture, and snowpack. CANGRD data are interpolated from adjusted and homogenized climate station data (i.e., AHCCD datasets). The relative trends reflect the percent change in total precipitation over a period from the baseline value (defined as the average over 1961-1990 as the reference period). Trend of Total Precipitation for 1948-2012 based on Canadian gridded data Seasonal and annual trends of relative total precipitation change (%) for 1948-2012 based on Canadian gridded data (CANGRD) are available, at a 50km resolution across Canada.

Precipitation totals 2012