The Southwest's average daily temperatures in 2001 to 2010 were the region's highest for any decade since 1900, says a new report coordinated by University of Arizona researchers.

The 500-page report on Southwest climate change was prepared by 120 scientists around the West and the nation, with five UA researchers as lead editors. Published by Island Press, the report also concludes that:

• Fewer cold waves and more heat waves occurred in the Southwest during 2001-10 than the averages for past decades since 1900. The Southwest's average temperature rose 1.6 degrees between 1901 and 2010.

• Depending on carbon-dioxide emission trends, average temperatures are expected to rise 1 to 4 degrees total by 2021-50, 1 to 6 degrees total by 2041-60 and 2 to 9 degrees total by 2070-99, compared to average temperatures in 1970-99.

• Flows in four major drainage basins, including the Colorado River's Upper Basin, were 5 percent to 37 percent lower from 2001-10 than their 20th-century average. The Upper Colorado's average flow from 2001-10 near Lake Powell was 16 percent lower than its 20th- century average.

• The frost-free growing season from 2001-10 was 17 days longer than the 20th-century average, and about a month longer than from 1900-10.

• The acreage that wildfires burned in the Southwest from 1987 to 2003 increased by more than 300 percent compared to the amount burned in the 1970s and 1980s.

• The region's ongoing drought is the most intense and severe since 1900, although the drought in the 1950s covered a larger area. But several droughts in the past 2,000 years lasted longer and were more severe than this one, tree ring records show.

• The average mortality of aspen in dry sites below 7,500 feet elevation was greater than 95 percent from 2000 to 2007. By 2030, the areas of forest whose climate is suitable for aspen growth is projected to drop by 10 percent to 40 percent.

• With some research showing earlier and longer springtime flower blooms, allergies and asthma may worsen for individuals who normally suffer from them, or become more widespread among the entire population.

• Climate change will exacerbate heat-related illness and death, and lead to increased particulate concentrations from wildfires and dust storms.

• Poor and other disadvantaged people will probably suffer most from climate change, because they will be disproportionately affected by increased extreme heat exposure.

• Climate change may disproportionately affect people along the U.S.-Mexico border. It will stress severely limited water systems, and reduce reliability of energy infrastructure, agricultural production, food security, and the ability to maintain traditional ways of life.

• Native American lands, people, and culture are likely to be disproportionately affected, because of endangered cultural practices, limited water rights, and social, economic, and political marginalization that are relatively common among indigenous people.

On StarNet

Read the transcript of Tony Davis' live blog of Thursday's Southwest Climate Assessment meeting at

Contact reporter Tony Davis at or 806-7746.