UA researchers contribute to new National Climate Assessment - Tucson News Now

UA researchers contribute to new National Climate Assessment

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The National Climate Assessment is due for release on Tuesday, May 6. The report reviews current climate change research and science, compiling information highlighting how warmer average temperatures impact the United States.

Eight University of Arizona researchers where part of the team that created the report. This includes Gregg Garfin, from U of A's Institute of the Environment, who was the lead author on the Southwest portion of the report.  

This is the third assessment released by the government. The last report was released in 2009.

The University of Arizona is hosting two events for the public to discuss the findings of this report. A panel discussion with National Climate Assessment experts and authors will be held on Thursday, May 8 at 7:00 PM in McClelland Park, Room 105 on the University of Arizona campus. On Friday, May 9, join an online Reddit conversation called "Ask Me Anything" from 11 AM to 12 PM. Two UAresearchers will answer questions about the report's findings.  

Climate change can have negative and positive impacts. Here in the Southwest many impacts are negative with health, drought, wildfire risk, and water availability all affected. While these factors are all common in the arid lands of the desert Southwest, hotter temperatures can intensify the severity of these conditions.

Heat stress is the leading cause of weather-related deaths in the United States, according to the National Weather Service. While heat waves are common in the desert, longer and hotter heat waves can take an increased toll on health, especially for elderly people.  

Forest health across the Southwest is also affected by climate change. According to the report, a number of computer models forecasting wildfire risk show a rise in danger. 

The report says "drought and increased temperatures due to climate change have caused extensive tree death across the Southwest. In addition, winter warming due to climate change has exacerbated bark beetle outbreaks by allowing more beetles, which normally die in cold weather, to survive and reproduce." 

Research indicates wildfire and beetles killed trees across 20 percent of Arizona and New Mexico forests between 1984 and 2008. 

This impact is already showing up in the numbers. While the number of wildfires over the years has decreased due to different management and firefighting techniques, the total area burned has increased in recent years. The image below compares the number of wildfires to the total acreage burned.  

Caption from report: Although the average number of wildfires per year (black line) has decreased over time, the total area burned by wildfires (red bars) in the continental U.S. (primarily in the Western states) has nearly doubled since 2000 relative to the long-term 1960-1999 average.

Data from the National Interagency Fire Center, for 1960 to 2011.


Once destroyed the forests may never look the same. Plants normally found a lower elevations could move farther up the mountain as climate change increases their range into previously cooler heights. 

According to the report "this threat is especially high in the sky islands of Arizona", which includes the mountain ranges here in Pima, Cochise, and Santa Cruz Counties. 

As climate change continues, snowpack in the western United States is forecasted to decline. This has a major impact on water availability. Deep snowpack melting slowly in the spring months is an important source of water for the rivers and reservoirs in the western United States. The image below shows the projected change in runoff due to climate change. The snowpack dwindles with forecasted warmer winters. 

Caption from report: These projections, assuming continued increases in heat-trapping gas emissions (A2 scenario), illustrate: a) major losses in the water content of snowpack that fills western rivers (snow water equivalent, or SWE); b) significant reductions in runoff in California, Arizona, and the Central Rocky Mountains; and c) reductions in soil moisture across the Southwest. The changes shown are for mid-century (2041-2070) as percentage changes from 1970-2000 conditions (Cayan et al. 2012).

For Arizona, this means the much needed water stored in reservoirs like Lake Mead, which feeds into the Central Arizona Project (CAP) canals, could be limited in the future.  CAP water is used to recharge the aquifer under Tucson, which is the main source of water for the metropolitan area.

And according to the report "Decreasing precipitation, rising temperatures, and drying soils are projected to increase irrigation and outdoor watering demand (which account for nearly 90 percent of consumptive water use) by as much as 35 percent by 2060."

Much of that irrigation and outdoor watering is done at area farms and orchards, which is a major part of the Arizona economy.  In some areas, notably Pinal County, farmland is being retired. This sometimes happens when cities and counties purchase the land to secure the water rights in an effort to plan for future water supply issues.  

The National Climate Assessment will not be available online until at least Tuesday May 6, 2014. Here is a link to the draft version released in January, 2014.

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