If Cutting Carbon Isn't Enough, Can Climate Intervention Turn Down the Heat? [View All]

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If Cutting Carbon Isn't Enough, Can Climate Intervention Turn Down the Heat?
Geoengineering could help stave off global warming, but it could also create some big problems
By Nikhil Swaminathan

If reducing carbon emissions fails to stop climate change, we may one day have the option of sending mirror-supporting satellites into space or filling the stratosphere with light-reflecting particles to block the sun's rays.
According to a new study, such measures could significantly cool Earth. But researchers caution that if they if they do not work or are suddenly halted, they could make matters worse.
"As far as I know, this is the first century-scale, time-dependent simulation of a geoengineering scheme," says Ken Caldeira, a climate scientist at the Carnegie Institution of Washington's Department of Global Ecology in Stanford, Calif., and senior author of the study published this week in Proceedings of the National Academy of Sciences USA. Geoengineering refers to activities designed to alter Earth's climate that may include blocking the sun, large-scale reforestation and sequestering carbon dioxide in the ocean.
First, Caldeira and his colleague, ecologist Damon Matthews, constructed a model to determine what would happen to the global climate if carbon dioxide emissions continued to increase at their current rate. Their findings: by 2100 Earth's surface temperature would have risen by an average of 3.5 degrees Celsius (6.3 degrees Fahrenheit) from what it had been in 1900, with temperatures in some parts of the Arctic jumping by as much as by as much as six degrees C (10.8 degrees F).

Next, the pair simulated the effect of adding a geoengineering scheme sometime between the years 2000 and 2075, which would result in the amount of radiation hitting the Earth being uniformly decreased. The authors' model predicts that temperatures in tropical regions would dip slightly (by 0.35 degree C or 0.63 degree F) and climb by a degree C (1.8 degrees F) the Arctic. In other words, the planet's average temperature would not change much from what it had been back in 1900.

"The positive result is you can ramp up geoengineering along with the carbon dioxide," Caldeira says. "Within a decade, you would get most of the cooling effect of a geoengineering scheme, and in two decades you'd get all of it."

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