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Home » Climate Change » Southwest Region

Southwest Regional Climate Change

California, Nevada, Arizona, Utah, Colorado and New Mexico

Information from the U.S. Global Change Research Program, June, 2009

Rising Temperature and Water Shortage

The southwest region includes the states of California, Nevada, Arizona, Utah, New Mexico and portions of Colorado and Texas. This region has experienced a more rapid rate of warming than any other region of the United States. Much of the spring stream flow here is a result of melting snow packs in the mountains. However, warmer winters have reduced the snow pack and that now reduces stream discharge in the spring.

The southwest has the most rapid population growth in the United States. Growing cities contribute to the urban heat island effect which will exacerbate the impact of rising temperatures - especially during the summer months.

The southwest has been in a water supply crisis for decades. High usage rates and a growing population have caused a significant depletion of ground water resources and overuse of surface water resources. Increasing temperatures will cause higher evaporation rates and reduce the amount of water available for stream flow and ground water recharge. Climate change will cause water challenges in the southwest to become much more difficult in the years ahead.

Recreation Opportunities Likely To Suffer
Kid Skiing
Unique tourism and recreation opportunities are likely to suffer. Rising temperatures will adversely affect winter activities such as downhill and cross-country skiing, snowshoeing, and snowmobiling. Later snow and less snow coverage are projected for ski resort areas, particularly those in the southern part of the region. Decreases from 40 to almost 90 percent are likely in end-of-season snowpack under high emissions scenarios in counties with major ski resorts from New Mexico to California. Photo copyright by iStockPhoto / A. Solovei.

Rising Temperature = Less Agricultural Land
Climate change and cropland
Increasing temperature, drought, wildfire, and invasive species will accelerate transformation of the landscape. Impacts of climate change on the landscape of the Southwest are likely to be substantial, threatening biological diversity, protected areas, and ranching and agricultural lands. Temperature increases have made the current drought in the region more severe than the natural droughts of the last several centuries. Record-setting wildfires are resulting from the rising temperatures and related reductions in spring snowpack and soil moisture. Photo copyright by iStockPhoto / J. Wynn.

Everyone Loses When Water Is Scarce
Climate change drought
Water supplies will become increasingly scarce, calling for trade-offs among competing uses, and potentially leading to conflict. Water is vital to agriculture, hydroelectric power production, the growing human population, and ecosystems. Water supplies in some areas are already becoming limited. Large reductions in spring precipitation are projected for the Southwest. Continued temperature increases combined with river flow reductions and rapid population growth will increase competition for water supplies. Photo copyright by iStockPhoto / C. Spencer.

Projected Spring Precipitation Change
Southwest US precipitation change map
Percentage change in March-April-May precipitation for 2080-2099 compared to 1961-1979 for a lower emissions scenario (left) and a higher emissions scenario (right). Confidence in the projected changes is highest in the hatched areas.

Observed and Projected Temperature Rise
Southwest projected temperature change
Percentage change in March-April-May precipitation for 2080-2099 compared to 1961-1979 for a lower emissions scenario (left) and a higher emissions scenario (right). Confidence in the projected changes is highest in the hatched areas.

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Map of southwest U.S.
Climate change will have a number of severe impacts on the southwestern states of California, Nevada, Arizona, Utah, Colorado and New Mexico. This page illustrates a number of the more significant impacts. Map by and MapResources.

Heat Waves May Cause Electric Blackouts
Heat wave
Cities and agriculture face increasing risks from a changing climate. With more intense, longer-lasting heat waves projected to occur over this century, demands for air conditioning are expected to deplete electricity supplies, increasing risks of brownouts and blackouts. Much of the region's agriculture will experience detrimental impacts in a warmer future, particularly specialty crops in California such as apricots, almonds, artichokes, figs, kiwis, olives, and walnuts. These and other such crops require a minimum number of hours below a chilling temperature threshold in the winter to set fruit for the following year. Photo copyright by iStockPhoto / J. DeLillo.

Flood Buffers Lost Due to Vegetation Die-Off
Flooding and climate change
Increased frequency and altered timing of flooding will increase risks to people, ecosystems, and infrastructure. Rapid landscape transformation due to vegetation die-off, wildfire, and loss of wetlands along rivers reduces flood-buffering capacity. Decreased snow cover on the lower slopes of high mountains and the increased fraction of winter precipitation falling as rain and therefore running off more rapidly also increases flood risk. Photo copyright by iStockPhoto / T. Campbell.

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