The U.K.’s highly respected Royal Society has released a study outlining two major potential methods of cooling the earth if mankind fails to slow global warming by reducing CO2 emissions: removing carbon dioxide from the atmosphere, and employing technologies to deflect solar radiation back into space. Stressing that emissions reductions were vital, the Royal Society nevertheless said that scientists must start investigating geo-engineering schemes to cool the planet. It said that CO2 could possibly be pulled from the air using various technologies, such as artificial trees and carbon sequestration, or by accelerating the reaction of rocks and minerals with CO2, which stores carbon dioxide. Land use changes and planting forests also could potentially play a smaller role, the group said. Methods to deflect solar energy back into space could include releasing stratospheric aerosols, pumping seawater into the atmosphere to produce more clouds, and launching mirrors or other devices into space to reflect the sun’s energy away from earth. The Royal Society dismissed a number of ideas as too risky, including a plan to seed the oceans with iron to stimulate the growth of CO2-absorbing algae. Last week, a group of British engineers suggested more modest and immediate ways to cool the planet.

This piece originally appeared on Yale Environment 360
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