To Slow Climate Change, Why Don't We Just Block the Sun?

Author:
Joe McCarthy

AP Photo/David Goldman, File

Imagine a capsule is launched 70,000 feet into the sky above Arizona and begins to release 100 grams of sulfur, calcium carbonate, or some other substance into the atmosphere. The device then floats back and forth through the ensuing cloud for the next several hours before it disperses, measuring chemical reactions and seeing how much sunlight is being blocked.

That’s basically how climate geoengineering, an emerging science that experts say has the potential to mitigate the worst consequences of climate change by cooling the planet and limiting the potential for extreme weather, works.

Proposed experiments in geoengineering hold great potential, but they've been dogged by doubts, fears, and misconceptions over what it means and how it would work.

And that skepticism has slowed the pace of research and prevented robust international dialogues from taking place, two conditions that experts say are essential to any future deployment of geoengineering technology.

Global Citizen recently spoke to multiple experts from scientific, legal, and diplomatic backgrounds about the prospects of geoengineering, its possible effects, and how it might be carried out.

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What Is Climate Geoengineering?

Solar geoengineering — releasing sun-blocking gases into the atmosphere — is the only known way to directly reduce global temperatures in the short-term.

The ideal outcome, according to proponents, would be pumping enough aerosols into the atmosphere to slow how fast the world is heating up and shave off a degree or two of projected temperature increases by the end of the century.

The past three years have been the hottest ever recorded, and a recent report by US government agencies predicted that temperatures could rise by about as much as 7.5 degrees Fahrenheit (4.8 degrees Celsius) by the end of the century if current trends continue.

“We are in a situation where countries basically recognize that you can’t reach that two degree goal without doing some kind of geoengineering,” Janos Pasztor, climate policy expert and executive director of the Carnegie Climate Geoengineering Governance Initiative, told Global Citizen.


The First Experiment in Geoengineering

The experiment described at the beginning of this story is being considered by Harvard University’s Solar Engineering Research Program, which received a grant of $20 million to further research and get more people to talk about it in international settings.

David Keith, who is helping to spearhead the initial experiment, spoke to Global Citizen about the program’s intentions.

“Broadly, I’m trying to promote a serious international effort, open-access, to understand better how well these solar geoengineering technologies could work, what their risks would be, and what the kind of options there would be for governance,” he told Global Citizen.

“[Currently] nothing is being done, it’s not being executed in any matter,” he added.

Keith said that the scale of the proposed experiment — releasing 100 grams of sulfur or another compound into the sky over Arizona — is as small as it can get and has no potential to impact the climate. It’s just a way to measure how certain chemicals act within the atmosphere and interact with other particles that are currently up there.

As a comparison, according to Keith, humans release more than 50 million tons of sulfur into the atmosphere each year through commercial activity, which is many orders of magnitude bigger than 100 grams.

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Sulfur, of course, has negative consequences such as causing acid rain, so other compounds are being considered, such as calcium carbonate, which could help to heal the ozone layer, but has unknown consequences as well.  

“We need a broader conversation, from a big variety of perspectives, particularly for the developing world,” Keith said. “There’s no single right answer right here.”


Doomsday Technology?

Solar geoengineering has been approached with caution so far, but even the thought of actively intervening in the climate strikes many observers as too extreme.

“There are ways that this could be misused that are horrifying,” Keith said. “You could freeze the world to the equator.”

If too much of a sun-blocking compound was released into the atmosphere, then, eventually, too little light and heat would reach the planet and it would create an ice age.

Keith emphasized that such a doomsday scenario is nearly impossible because it could only be triggered through deliberate action over decades. If any country or actor attempted such a thing, the rest of the world would intervene, he said.

“That would only work if there was a collective agreement by the human race to commit suicide,” he said.

Another line of argument is that injecting aerosols into the atmosphere would rearrange precipitation patterns around the world, leading to droughts and flooding.

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Keith responded by saying that climate change is already doing that in extreme ways that affect the world’s most vulnerable and that existing models show that geoengineering can reverse these trends.

“The model shows doing solar engineering is particularly effective at reducing cyclone activity,” he said. “And reducing extreme precipitation and peak temperature and those are the things that have the most human damage.”

David Dana, a legal scholar at Northwestern University who studies the subject, believes that the risks of solar geoengineering are too great and that the potential for abuse is too rife for it to be pursued.

He said that there are three chief concerns surrounding geoengineering — that it will deter other forms of climate action, that many risks are unknown, and that no international framework exists to monitor its use.

Many environmentalists worry that the availability of solar geoengineering removes incentives to cut emissions. If climate change can be halted in this way, then why change the status quo?

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That would leave the underlying causes of climate change untouched, and would create an unsustainable system of climate management, he said.

“You still have greenhouse gases accumulating in the atmosphere,” Dana said. “You’re just pushing it off, just temporarily avoiding it.


The Ideal Solution: All of the Solutions

Pasztor agreed that climate geoengineering can only be a supplement to cutting emissions, but that is has to be seriously considered because global emissions are projected to heat the planet at catastrophic levels.

He said that there has to be a combination of mitigation, adaptation, solar geoengineering, and greenhouse gas removal.

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Everyone agrees that the issue needs more discussion and that international frameworks have to be developed.

“It’s a slow and difficult diplomatic process to get anything decided,” Pasztor said. “Once you decide, how do you set up an institution that is able to actually deliver solar engineering on an ongoing basis for decades possibly for centuries?”

There are technical questions of how geoengineering would be done, governance questions of who would oversee its implementation, ethical questions of who would be impacted, and much more.  

The Paris climate agreement hints at the need for some sort of climate manipulation, by saying that the world needs to achieve “negative emissions.”

Solar geoengineering doesn’t reduce emissions, but it does counteract the effect of rising greenhouse gases.

The only way to know its potential is to bring the subject into the sunlight.

“Because the stakes are so high,” Pasztor said. “We have to start talking about it.”