Q: What is geoengineering?
A: Geoengineering literally means “Earth-engineering.”
It is a term that describes how people could intervene in Earth’s functions to slow down or reverse the effects of climate change.
Current discussions of geoengineering focus on two broad categories to reduce global warming.
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The first general idea is to cool the planet by reducing the amount of solar energy it absorbs. This could be done by increasing the amount of solar energy reflected back to space.
One approach is to build space reflectors, which would block a small portion of sunlight by reflecting the energy away from Earth.
Another proposed technique is to inject aerosols into the stratosphere. This approach attempts to replicate the effect of explosive volcanic eruptions, such as Mount Pinatubo in 1991. That eruption spewed tiny aerosols into the stratosphere that scattered sunlight back into space, which over the next 15 months decreased the average global temperature by about 1 degree.
The second category of ideas seeks to remove carbon dioxide from the atmosphere and thus reduce its accumulation in Earth’s atmosphere. Carbon geoengineering proposals posit that carbon can be removed from the atmosphere on a massive, global scale using a combination of biological and mechanical methods. Global-scale tree planting is one example. Another is to build large machines that directly remove atmospheric carbon dioxide and store it elsewhere.
Geoengineering comes with risks and significant uncertainties. Intervening in a complex system can give unexpected results. While there may be global benefits, local impacts could vary widely and may not benefit the region — for example, shifts in precipitation patterns leading to local droughts. There is also the question of economic cost as some of the proposed techniques are costly.
"Weather Guys" Steve Ackerman and Jonathan Martin are professors in the University of Wisconsin-Madison department of atmospheric and oceanic sciences.