Geoengineering: a quick fix with big risks

June 5, 2007

Radical steps to engineer Earth’s climate by blocking sunlight could drastically cool the planet, but could just as easily worsen the situation if these projects fail or are suddenly halted, according to a new computer modeling study.

The experiments, described in the June 4 early online edition of The Proceedings of the National Academy of Sciences, look at what might happen if we attempt to slow climate change by “geoengineering” a solar filter instead of reducing carbon dioxide emissions. The researchers used a computer model to simulate a decrease in solar radiation across the entire planet, but assumed that that the current trend of increasing global carbon dioxide emissions would continue for the rest of this century.

“Given current political and economic trends, it is easy to become pessimistic about the prospect that needed cuts in carbon dioxide emissions will come soon enough or be deep enough to avoid irreversibly damaging our climate,” said co-author Ken Caldeira of the Carnegie Institution’s Department of Global Ecology. “If we want to consider more dramatic options, such as deliberately altering the Earth’s climate, it’s important to understand how these strategies might play out.”

Although the term “geoengineering” describes any measure intended to modify the Earth at the planetary scale, the current study focuses on changes that reduce the amount of solar radiation that reaches the planet’s surface. Several methods to accomplish this have been suggested, from filling the upper atmosphere with light-reflecting sulfate particles to installing mirrors in orbit around the planet.

According to the model, even after greenhouse gases warm the planet, geoengineering schemes could cool off the Earth within a few decades to temperatures not seen since the dawn of the industrial revolution. This is good news, according to Caldeira and lead author Damon Matthews of Concordia University in Montreal, Canada, because it suggests there is no need to rush into building a geoengineering system before it is absolutely necessary.

However, the study also offers some bad news. If any hypothetical geoengineering program were to fail or be cancelled for any reason, a catastrophic, decade-long spike in global temperatures could result, along with rates of warming 20 times greater than we are experiencing today.

“If we become addicted to a planetary sunshade, we could experience a painful withdrawal if our fix was suddenly cut off,” Caldeira explained. “This needs to be taken into consideration if we ever think seriously about implementing a geoengineering strategy.”

Caldeira and Matthews believe that lower temperatures in a geoengineered world would result in more efficient storage of carbon in plants and soils. However, if the geoengineering system failed and temperatures suddenly increased, much of that stored carbon would be released back into the atmosphere. This, in turn, could lead to accelerated greenhouse warming.

Reduced solar radiation not only affects temperatures in the simulations, but also global rainfall patterns. In a model run with no simulated geoengineering, warmer temperatures resulted in more rainfall over the oceans, while increased carbon dioxide levels caused a decrease in evaporation from plants’ leaves, and consequently a decrease in rainfall over tropical forests. In contrast, the geoengineering scenario—which had lower temperatures but the same high levels of carbon dioxide—resulted only in a decrease in tropical forest rainfall.

“Many people argue that we need to prevent climate change. Others argue that we need to keep emitting greenhouse gases,” Caldeira said. “Geoengineering schemes have been proposed as a cheap fix that could let us have our cake and eat it, too. But geoengineering schemes are not well understood. Our study shows that planet-sized geoengineering means planet-sized risks.”

Caldeira feels it is important to develop a scientific understanding of proposed geoengineering schemes. “I hope I never need a parachute, but if my plane is going down in flames, I sure hope I have a parachute handy,” Caldeira said. ”I hope we’ll never need geoengineering schemes, but if a climate catastrophe occurs, I sure hope we will have thought through our options carefully.”

Source: Carnegie Institution

Explore further: Engineering climate: from pariah to saviour?

Related Stories

Engineering climate: from pariah to saviour?

December 12, 2015

Once dismissed as dangerous science fiction, schemes to stave off global warming by re-engineering Earth's climate may well gain in traction as a result of the Paris agreement.

Paris climate goals mean emissions need to drop below zero

December 24, 2015

If governments are serious about the global warming targets they adopted in Paris, scientists say they have two options: eliminating fossil fuels immediately or finding ways to undo their damage to the climate system in the ...

Mars compared to Earth

December 7, 2015

At one time, astronomers believed the surface of Mars was crisscrossed by canal systems. This in turn gave rise to speculation that Mars was very much like Earth, capable of supporting life and home to a native civilization. ...

Can geoengineering put the freeze on global warming?

March 21, 2011

Scientists call it "geoengineering," but in plain speak, it means things like this: blasting tons of sulfate particles into the sky to reflect sunlight away from Earth; filling the ocean with iron filings to grow plankton ...

Recommended for you

Online shopping might not be as green as we thought

February 5, 2016

Logic suggests that online shopping is "greener" than traditional shopping. After all, when people shop from home, they are not jumping into their cars, one by one, to travel to the mall or the big box store.

Long-term global warming not driven naturally

February 1, 2016

By examining how Earth cools itself back down after a period of natural warming, a study by scientists at Duke University and NASA's Jet Propulsion Laboratory confirms that global temperature does not rise or fall chaotically ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.