Blocking The Sun With Chemicals Isn't so Crazy, Says Harvard

A new study proposes solar geo-engineering has more validity than previously thought.
Jessica Miley

Geo-engineering is the branch of engineering that proposes large-scale manipulation of environmental processes in a bid to mitigate or slow climate change. These ideas range from building covers for the oceans to propping up ice shelves. 


Unsurprisingly these ambitious ideas are met with skepticism from many who question whether they will work at all and at what greater cost to the environment

But now, scientists from Harvard suggest that one popular geo-engineering idea may have merit. The proposition involves spraying chemicals into the air to block the sun’s rays. 

Sun-blocking could correct climate change

A new study from the esteemed university says that careful use of the sun-blocking chemicals could reflect sunlight enough to help cool the planet.

“Some of the problems identified in earlier studies where solar geo-engineering offset all warming are examples of the old adage that the dose makes the poison,” said David Keith, the Gordon McKay Professor of Applied Physics at SEAS and senior author of the study. 

“This study takes a big step towards using climate variables most relevant for human impacts and finds that no IPCC-defined region is made worse off in any of the major climate impact indicators. Big uncertainties remain, but climate models suggest that geoengineering could enable surprisingly uniform benefits.” 

The study is careful to point out that the spraying will only work in tandem with an effort to cut emissions on earth. One of the biggest risks of a sun-blocking proposition is its effect on rainfall. 

Advanced model used for the first time

To figure out exactly the limits of sun-blocking the geoengineers used an advanced computer model to simulate extreme rainfall and tropical cyclones. The researchers looked at temperature and rainfall extremes and as well as water availability and the intensity of tropical storms. 

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They found that the careful use of solar geoengineering will have whole Earth cooling effect as well as moderating extreme rainfall in many places and offsets more than 85 percent of the increase in the intensity of hurricanes. Incredibly the study suggests that the proposed solar reflection would result in less than 0.5 percent of the land experiencing exacerbated effects due to climate change. 

Drop assumptions about winners and losers

“The places where solar geoengineering exacerbates climate change were those that saw the least climate change to begin with,” said Peter Irvine, Postdoctoral Research Fellow at SEAS and lead author of the study.


“Previous work had assumed that solar geoengineering would inevitably lead to winners and losers with some regions suffering greater harms; our work challenges this assumption. We find a large reduction in climate risk overall without significantly greater risks to any region.” 

The authors of the study understand the model has its limitations and makes some assumptions, but they say it's the first time such a comprehensive model has been used to understand how geoengineering can be used in combination with other climate change reduction efforts. 

"For years, geoengineering has focused on compensating for greenhouse gas induced warming without worrying too much about other quantities like rainfall and storms,” said Kerry Emanuel, the Cecil & Ida Green Professor of Atmospheric Science at MIT and co-author of the study.

“This study shows that a more modest engineered reduction in global warming can lead to better outcomes for the climate as a whole."

“The analogy is not perfect, but solar geoengineering is a little like a drug which treats high blood pressure,” said Irvine.

“An overdose would be harmful, but a well-chosen dose could reduce your risks. Of course, it’s better to not have high blood pressure in the first place, but once you have it, along with making healthier lifestyle choices, it’s worth considering treatments that could lower your risks.” The research is published in Nature Climate Change.

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