We are getting closer to the point where we may have to employ emergency engineering solutions to cool the planet, according to panelists at a geoengineering session during last week's Aspen Environment Forum.

"Given the inertia of the climate system, that CO2 stays there, like nuclear waste, we might get to a situation where no amount of [emissions] cuts will solve the problem," said David Keith, director of the Energy and Environmental Systems Group at the Institute for Sustainable Energy Environment and Economy. "We may be there today, so we cannot take the option off the table."

If we needed a quick fix we could spray reflective sulfate aerosol particles into the upper atmosphere, "where they would cool the planet and partially and imperfectly offset the impacts of climate change," Keith said.

"We are certain if you do it, it will get colder quickly," but there is uncertainty about the side effects and cost effectiveness, he said.

Ken Caldeira, a climate scientist at the Carnegie Institution and professor of global ecology at Stanford University, said we can be somewhat certain that pumping particles into the sky, to reflect heat back into space, will cool the climate without catastrophic consequences.

He points to the 1991 eruption of Mt. Pina-tubo in the Philippines, which sent millions of tons of sulphur dioxide into the air, reducing global temperatures by half a degree Celsius, and only slightly damaging the ozone layer.

Other cooling ideas that have sprung up in the last few decades: installing reflective chips on the ocean, dumping iron filings into seas to encourage the growth of carbon-trapping phytoplankton, re-icing the Arctic, sending reflective material into space to bend some of sun's rays away from Earth, and cloud whitening, as well as whiter roofs, roads, and crops.

The dialogue has been hushed in part because of concern over people abandoning mitigation in favor of engineering--a potentially quick and easy, last minute solution.

But now it may be a way to buy time while we figure out how to reduce emissions, panelists said.

For engineering to work to our benefit, there needs to be more funding put into researching and testing these ideas, said Caldeira, who estimates that the costs of engineering solutions would be about 1 percent of the cost of cutting emissions--$500 billion a year, according to Keith.

"The argument for research now is almost overwhelming," said Keith. "The worst case is where we think it works and it doesn't."

"We need international coordination so someone isn't pulling a knob one way and another is pulling it another way. With the climate system… we don't understand how change in one place results in other changes elsewhere."

Without more research, Keith said, "I don't think humans are ready to control climate. I fear a kind of runaway… is could be just a disaster."

Photograph of the 2003 Anatahan Volcanic eruption courtesy NOAA.

The Aspen Forum is sponsored by the Aspen Institute, the National Geographic Society, Shell, Duke Energy, and General Motors.

—Tasha Eichenseher

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