14 December 2009

Climate Change in the West

Posted by Michael McFadden

A battery of eight talks starting at 8 a.m. and covering none less but the serious topic of climate change in the western United States can leave one a little shell-shocked. But the speakers’ broad reviews of the science helped catch generalists up to speed and provided at least some hopeful news.

Michael Dettinger, a hydrologist with both the US Geological Survey and the Scripps Institution of Oceanography, UCSD in La Jolla, Calif., kicked off the session with an overview of predictions for temperature and precipitation-related changes in the West.  Thirteen climate models unanimously predict a rise in temperatures over the next century.

The good news for California: due to its marine climate its temperature rise is projected to be less than that of other states. The bad news: California’s hydrology and water supply is highly sensitive to even slight changes in warmth, because it depends on snowpack. Small changes in temperature may cause snow to melt sooner, exacerbating winter floods and summer droughts.

Though models disagree somewhat on how precipitation will change as a consequence of rising greenhouse gas concentrations, more precipitation may not mean more available water because rising temperatures cause increases in evapotransporation.

Hydrologic models show that surface runoff in different regions in the west will respond differently to changes in precipitation and temperature, said Tapash Das, a postdoctoral researcher at the Scripps Institution of Oceanography, UCSD in La Jolla, Calif.

An innovative communal effort aims to improve climate change models, according to Philip Mote, the director of the Oregon Climate Change Research Institute at Oregon State University (Corvallis). He talked of a project that uses tens of thousands of volunteers around the world to tweak model parameters and better understand how model uncertainties affect variables like temperature and precipitation. He is still looking for more volunteers.  More about the project is found here.

Predicted climate changes will worsen fire seasons in the western U.S. in the next century, said John Abatzoglou, a geographer at the University of Idaho in Moscow, Idaho. More regions will have long spells of extreme fire danger, stretching available resources for fighting wildfires. Work by Karen McKinnon and collaborators at the Department of Earth and Planetary Sciences, Harvard University, in Cambridge, Mass., evaluated the possible role of human-caused climate change in the Pacific Northwest’s 2001 drought.

Kelly Redmond, deputy director of the Western Regional Climate Center at the Desert Research Institute in Reno, Nev., reviewed observed changes in climate during the past 115 years. A few key points: annual amounts of rain and snow have varied greatly in the last 35 years, even where long-term averages have stayed the same. And low temperatures are rising the most. Based on observations of plants, spring may come sooner or later in various regions in the west in the future, said Jeremy Weiss, a geoscientist at the Arizona State University in Tucson.

In less gloomy news: Some plants may live through climate change in a safe place. Constance Millar, a paleoecologist with the US Forest Service, stationed in Albany, Calif., considered the role of refugias—areas where regional plants (or animals) may ride out climate changes—which more scientists are seeing as a way to protect biodiversity in the next century. She described how redwoods and other long-living trees have survived warm and cool periods for millions of years. Regions with patchy climates, for instance, have helped plants survive large changes in climate in the past. Human-made refugia, such as seed-banks, will also help.

–Olga Kuchment, UC Santa Cruz Science Communication Graduate Student