Microsoft Word - southwest.doc

The Southwest is projected to warm by 4-6°F under lower-emissions and 7-10°F under higher-emissions scenarios by the end of the century. The region faces severe water scarcity, expanding deserts, and reduced runoff, particularly in the Colorado River system. Public health risks include increased heat-related deaths in Los Angeles and worsening air quality. Economic threats include reduced yields for California specialty crops, diminished ski resort profitability due to snowpack loss, and reduced aircraft freight capacity at high-altitude airports like Phoenix and Denver. Biodiversity is critically threatened, especially in the Madrean Pine-Oak Woodlands, while mountain ecosystems face range reductions and reproductive failures in wildflowers due to earlier snowmelt and spring frosts.

• The Southwest is projected to warm between 4 and 6°F under a lower-emissions scenario and between 7 and 10°F under a higher-emissions scenario by the end of the century, with recent warming already exceeding the global average in some areas.
• The region is expected to become drier, with deserts expanding north, east, and upward in elevation. Water scarcity is increasing as groundwater pumping lowers water tables and rising temperatures reduce river flows, including the Colorado River.
• The Colorado River system is highly vulnerable; between 1999 and 2007, the system lost approximately half of its storage following the worst drought in 100 years. Future climate-driven flow reductions will challenge water managers' ability to meet the demands of a growing population.
• Climate change is expected to exacerbate health risks in California. In Los Angeles, annual heat-related deaths by the 2090s could increase two to three times under lower emissions and five to seven times under high emissions compared to the 1990s baseline. Air pollution days could increase by 25-35% (lower emissions) or 75-85% (higher emissions) in Los Angeles and the San Joaquin Valley.
• Agricultural productivity in California is threatened by a reduction in winter chilling hours required for specialty crops like almonds, walnuts, and apricots. Estimated losses for wine and table grapes, almonds, oranges, walnuts, and avocadoes range from zero to 40 percent.
• Infrastructure and tourism are at risk: ski resorts from New Mexico to California may see end-of-season snowpack decrease by 40 to 90 percent under high emissions. Additionally, higher temperatures reduce aircraft lift, with projected freight capacity reductions by 2030 of 17% at Denver airport and 9% at Phoenix airport.
• Biodiversity is severely impacted, particularly in the Madrean Pine-Oak Woodlands, which has already lost over 70% of native vegetation. In California, two-thirds of over 5,500 native plant species may see range reductions up to 80% by the end of the century.

APA

Union of Concerned Scientists (n.d.). Microsoft Word - southwest.doc. https://www.ucs.org/sites/default/files/2019-09/us-global-climate-change-report-southwest.pdf

Chicago

Union of Concerned Scientists. Microsoft Word - southwest.doc. n.d. https://www.ucs.org/sites/default/files/2019-09/us-global-climate-change-report-southwest.pdf.

Wikipedia

{{cite report |author=Union of Concerned Scientists |title=Microsoft Word - southwest.doc |url=https://www.ucs.org/sites/default/files/2019-09/us-global-climate-change-report-southwest.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{unionofconcernedscientistsndmicrosoft, author = {{Union of Concerned Scientists}}, title = {{Microsoft Word - southwest.doc}}, institution = {Union of Concerned Scientists}, url = {https://www.ucs.org/sites/default/files/2019-09/us-global-climate-change-report-southwest.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }