Talk of manipulating Earth's climate

WASHINGTON -- The idea seems like something out of a Superman comic: A machine or missile shoots tons of particles into the atmosphere that would block the sun's rays, cool down the overheated Earth, and reverse global warming.

But today some of the country's leading minds in science, history, and economics will gather in a closed session organized by NASA and Stanford University to discuss researching such a strategy -- a subject long taboo in environmental circles because so much could go wrong. Some fear it would be seen as a quick fix, replacing the need to reduce fossil fuel emissions, but others contend that the world needs an emergency plan in case global warming triggers a catastrophe, such as a break up of the Greenland ice sheet and massive flooding in coastal regions.

"Is it better to let polar bears go extinct and let the ice sheets melt? Is it worse to inject some aerosols into the stratosphere that could deflect some sunlight?" said Ken Caldeira , a climate scientist at the Carnegie Institution's Department of Global Ecology at Stanford University, which is hosting the two-day meeting.

The idea is called geoengineering: using technology to tinker with the Earth's delicate climate balance. Many scientists doubt it is possible. Even those who have studied the idea worry about the possible misuse of their research.

Those scientists who believe it could work point to the eruption of volcanoes in which masses of particles have deflected sunlight and reduced global temperatures by an average of 0.9 degrees.

Caldeira, who conducted various models of geoengineering while at Lawrence Livermore National Laboratory in the past decade, said he is "philosophically opposed" to the use of geoengineering without first reducing greenhouse gas emissions. But he said his modeling shows the idea works.

"We found that if you blocked 20 percent of the sunlight over the Arctic Ocean, it would be enough to restore sea ice," he said. "That would be blocking 1/300th of the entire sunlight hitting the Earth, but focusing it on the Arctic would prevent the ice from melting."

The notion of tinkering with the Earth's climate is not new, dating at least to 1839, when James Espy , who would become the United States' first meteorologist, tried to produce rain using updrafts from large fires, said James R. Fleming , a professor of science, technology, and society at Colby College in Waterville, Maine. Fleming is researching climate change this year at the Woodrow Wilson International Center for Scholars in Washington

Fleming said militaries have long wanted the power to manipulate climate, and that worries him in relation to geoengineering

"This seems to be a relatively heroic response to climate warming, but it does have the possibility of getting out of hand," without controls over who could use the technology, Fleming said.

Still, very few people know anything about geoengineering. Congress hasn't held hearings on it, and the recent 700-page report by the British government on climate change's impact on the global economy didn't mention it once.

So far, talk has circulated among a small group of intellectuals. An editorial essay earlier this year in the journal Climatic Change by Nobel laureate Paul J. Crutzen prompted this weekend's gathering.

In his paper, Crutzen said the best way to fight global warming "is to lower the emissions of the greenhouse gases. However, so far, attempts in that direction have been grossly unsuccessful."

While he called geoengineering proposals "by far not the best solution," they should be "explored and debated."

The Earth's temperature has risen about 1.4 degrees in the past century, largely because emissions of carbon dioxide from power plants and cars become trapped in the atmosphere. Scientists predict that at the current rate of growth of carbon dioxide emissions, the global temperature could increase between 3.5 and 7 degrees in the next 50 years.

"To me, we're on a mass extinction path that would take several centuries to unravel," Caldeira said.

Scott Barrett , an economist who researches environmental policy at Johns Hopkins University , said he had always avoided the subject of geoengineering, but he became "so depressed about the prospects for reducing emissions on a substantial scale. I believe we need to consider the alternatives -- including this one."

"Imagine," he said, "you are standing on a precipice and you see something bad happening, and the only thing you could really do is geoengineering. Well, you'd really like to have this in your back pocket in case you need it."

The costs vary , from $100 million to tens of billions , and scientists say the interventions may have to be done annually.

Henry D. Jacoby , codirector of the Global Change Joint Program at the Massachusetts Institute of Technology , said more scientific examination was needed.

"We really have only a limited understanding in the world system, and how we impact it now, and how the Earth responds to the greenhouse ga ses now," he said. "The notion we would then intentionally do something to correct that, to change the balance of the Earth by some specific action, well, I'd be very cautious about that."

Fleming, the Colby researcher, said the best way to proceed on geoengineering was to involve people from all over the world. "We should talk about this, and talk about it in the open with a full range of perspectives ."

John Donnelly can be reached at donnelly@globe.com.