Scientists recommend change now to lessen climate-change effects

By Melissa Fusco

Scientists at a Feb. 21 panel, "Carbon, Climate and Consequences," recommended immediate action to lessen the dire effects of global climate change. The panel was the second in a three-part "End of Oil" series, co-sponsored by the School of Earth Sciences and the Ward W. and Priscilla B. Woods Institute for the Environment at Stanford University.

"We will see the changes in our lifetimes, and we must decide what kind of world we want to live in in the future," said Michael Mastrandrea, a fellow at the Center for Environmental Science and Policy.

The panel's first speaker was Azadeh Tabazadeh, an associate professor of geophysics and of civil and environmental engineering. Tabazadeh told an audience at the packed event in the Arrillaga Alumni Center that the Earth's greenhouse gas concentrations have risen exponentially in the last 200 years. The increase coincides with an exponential rise in human population, strongly suggesting that the increase was manmade. Current models predict that carbon dioxide in the atmosphere will increase from about 380 parts per million today to 550 to 900 parts per million by the century's end.

The presence of excess carbon dioxide and other greenhouse gases in the atmosphere causes the planet to trap more heat than it reflects. "Every second, the Earth hangs on to one surplus Watt of solar heat per square meter," Tabazadeh explained. "It's the equivalent of a miniature Christmas light burning continuously over every square meter of the planet's surface."

By 2100, the increase in carbon dioxide alone is predicted to increase surface temperatures by 2 to 5 degrees Celsius (4 to 9 degrees Fahrenheit), Tabazadeh said.

Geological and environmental sciences Professor Rob Dunbar, the second speaker, explained how researchers use ice cores to gather information about temperature and atmospheric flux. These long cylinders of solid ice are drilled from glaciers that are thousands of years old.

"Microscopic gas bubbles in the ice cores literally give us gas samples of the ancient atmosphere," he noted. "We can extract that and measure very accurately the composition of carbon dioxide and methane at different points in history."

The ice core data, Dunbar said, gives scientists a data set to test the hypothesis that greenhouse gas variations cause temperature change. "Everywhere, we see carbon dioxide vary with temperature," he said.

While temperature increases of a few degrees may not seem significant, Dunbar cautioned that the long-term global implications are enormous. The water that melting glaciers and permafrost unleash will contribute to storms, rising oceans and changes in rainfall in the Earth's lower latitudes, where most of the planet's population lives.

Dunbar criticized climate skeptics, who claim the evidence for global warming is not strong enough to warrant policy changes. He contrasted the position of British Prime Minister Tony Blair, who in 2004 called global climate change "the world's greatest environmental challenge," with comments made by U.S. Sen. James Inhofe (R-Okla.), chairman of the Senate Committee on Environment and Public Works, who suggested in 2003 that global warming was a "hoax" perpetrated by scientists.

"I still have such a visceral reaction to this claim," Dunbar told the audience. "The community does a good job policing itself, and we are trained to be skeptical. The notion that there is an organized cabal conjuring up a climate-change scare is just plain silly."

Mastrandrea, the final speaker, focused on the consequences of greenhouse gas emissions for California's environment and economy.

Plotting temperature increases that are predicted by current climate models, he presented two different scenarios for California. The first represented "business as usual," based on the state's current emissions rates. The second represented a lower emissions trajectory urged by environmentalists.

The projected temperature increase in both scenarios stays fairly low through the 2030s, but diverges sharplyby as much as 8 degrees Celsius (14 degrees Fahrenheit)thereafter. On its current emissions path, California faces summer temperature increases of up to 10 degrees Celsius (18 degrees Fahrenheit) by the end of the century.

In particular, the choices California makes now will affect the Sierra snow pack, which currently supplies about half the state's water supply through the spring and summer months. This natural reservoir is shrinking because higher temperatures cause it to retain less snow and ice during the winter. California's wine industry also is especially vulnerable to climate change and is already beginning to suffer the effects of warming, Mastrandrea said. Wine grapes are particularly sensitive to temperature.

The situation calls for "a blend of adaptation and mitigation," Mastrandrea said. "At this point, some impacts are going to be unavoidable."

He urged audience members to support environment-friendly legislation and to make conservation a priority. He also stressed the difference that individual consumers can make by purchasing energy-efficient appliances, turning off lights and switching from regular light bulbs to fluorescents, which are three to four times more efficient.

Melissa Fusco is a science-writing intern at Stanford News Service.