LAKE TAHOE and#8212; With Lake Tahoe temperatures up by a 2-degree average since 1939, scientists are studying how warmer weather could affect the lake’s environment and ecology.

and#8220;There is definitely global warming going on,and#8221; said Jim Ashby, a climatologist with the Western Regional Climate Center out of Reno. and#8220;The question is how much of the rise (in temperature) is due to global warming and how much is due to development.and#8221;

While Lake Tahoe has not seen as dramatic of an increase in temperature as Reno, temperatures have increased from an average of 42.37 degrees between 1939 to 1948, to 44.62 degrees between 1999 and 2008, according to WRCC data.

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Tahoe is a prime place to compare temperatures to determine the effects of global warming because it is not an urban area, Ashby said. Because it does not have dense development, the temperature increases in Tahoe are more likely to be reflective of global warming trends, he said.

A dry forecast

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A study commissioned last week by the National Science and Technology Council and released by the Subcommittee on Global Change Research details effects of climate change in the U.S., specifically in different regions of the country. It predicts temperatures in the southwest area of the United States, which includes Nevada, California and Lake Tahoe, could rise 4 to 10 degrees by 2090.

In this scenario the report details a number of situations that could happen regarding wildfire risk, precipitation fall, vegetation and flooding.

One of the major changes outlined by the report and other local researchers is that more precipitation will fall in the form of rain, and the snow that does fall will melt sooner in the season.

and#8220;The studies show that runoff and stream flow will decrease in the summer months but will increase in the winter months,and#8221; said California Energy Commission senior engineer Guido Franco.

This could result in increase drought and flooding in the southwest, according to the report.

The change in precipitation patterns could also negatively affect recreation and tourism, according to the report. The scenario projected in the report indicates later snow and less snow coverage in ski resort areas. End of season snowpack could decrease up to 40 to 90 percent. Add on to that shorter snow seasons and earlier wet snow avalanches, and some resorts could be forced to shut down runs earlier, according to the scenario released in the report.

and#8220;Even in non-winter months, ecosystem degradation will affect the quality of the experience for hikers, bikers, birders and others who enjoy the southwest’s natural beauty,and#8221; the report reads. and#8220;Water sports that depend on the flows of rivers and sufficient water in lakes and reservoirs are already being affected and much larger changes are expected.and#8221;

In the case of warmer temperatures, the report explains that changing precipitation patterns will create declines in high elevation ecosystems like alpine forests and tundra. High elevation forests in California could decline by 60 to 90 percent before the end of the century, according to the report.

and#8220;There might be a shift in the vegetation pattern,and#8221; Franco said. and#8220;Some of the trees may not be there in the future.and#8221;

Fires in wetter, forested areas could increase in frequency while areas where fire is limited by the availability of fuels could decrease, according to the Subcommittee on Global Change Research report.

Localizing the issue

While the report’s research covers a broad area of the country, scientists at the Tahoe Environmental Research Center are using similar data to narrow down a scenario for Lake Tahoe.

That research includes modeling possible temperature changes for the Basin and seeing how those will eventually affect pollutant and sediment loading into the lake.

and#8220;Even now there are not many people in the Tahoe Basin who really have an idea of how climate change will affect the pollutant load,and#8221; said John Reuger, TERC associate director.

TERC’s new study, which could possibly release results by the end of the calendar year, would show how increased rain and earlier snowpack melting could affect Best Management Practices installed around the Basin.

and#8220;We’re at the point of saying and#8216;how will this phenomenon affect us here and does it have any really big implications for management strategies,’and#8221; Reuger said.

Read more

To view the full study, visit http://www.globalclimatechange.gov/usinpacts.