In a lab at Harvard, researchers are trying to replicate the conditions of the stratosphere – the part of the atmosphere that stretches roughly six to 31 miles above the surface of the planet-in test tubes. Their goal: to better understand what would happen if humanity eventually decides to embark on a radical, controversial plan to temporarily cool the planet by spraying clouds of particles into the sky. the sky to release particles of a compound like sulfur dioxide that can reflect some sunlight back into space and could temporarily cool the planet. It's not a fix for climate change, and it's a form of geoengineering so extreme that it carries risks that may not be fully predictable. But as climate change progresses, it is possible that the global community may someday decide it will have to try it.
"Our team is doing research because we believe there is still a lot of uncertainties around solar geoengineering, and we think there's a "says Elizabeth Burns, managing director of Harvard's Solar Geoengineering Research Program. Zhen Dai and Marie-Anna Boggio-Pasqua conduct a flow tube experiment to test stratospheric heterogeneous chemistry of solar geoengineering
In a new study in Nature Climate Change researchers from Harvard, MIT, and Princeton used a state-of-the-art, detailed computer model to look at what might happen if solar geoengineering was used to cut global temperature increases in half. In the scenario, they found that reducing warming would also offset the increasing intensity of hurricanes and would help moderate extreme rain and lack of water for farming (in the model, rain decreased but so did evaporation). Less than 0.5% of the world may see increases in climate change impacts. This is in contrast to some previous studies that found that this type of geoengineering could benefit some parts of the world while large other areas were harmed. Still, the study is limited, and does not look at all of the potential effects
The concept of spraying chemicals into the sky to cool the Earth is not new. It's the same process that happens naturally when the volcanoes erupt. In 1
Burns has repeatedly emphasized that the world's priorities are to reduce emissions to zero. "Solar geoengineering can not be a substitute for reducing emissions, because it does not address the root cause of climate change," she says. "So if we are to achieve a stable climate, we really need to reduce emissions to zero, and then eventually remove the carbon dioxide that's in the atmosphere and store it underground or elsewhere. These actions actually address the root cause. Solar geoengineering does not. "
" It would only potentially be used temporarily while we rapidly reduce our emissions to the atmosphere and figure out how to separate carbon dioxide out, "says Alan Robock, an environmental sciences professor at Princeton. "So nobody talks about doing it instead of mitigation. "Robock has documented 27 potential risks of the idea, from the possibility of ozone depletion to potential droughts and a reduction in solar energy generation. The paper lists only six potential benefits, but one is significant: a reduction in surface air temperatures could "reduce or reverse the negative impacts of global warming, including floods, droughts, stronger storms, sea ice melting, and sea level rise."  At Harvard, researchers are exploring the possibility of using calcium carbonate (the same particle found in chalk or toothpaste) instead of sulfur dioxide; while sulfur dioxide could speed up the destruction of the ozone layer, calcium carbonate could potentially help it and avoid some other risks. While their work is focused on lab and computer modeling now, the team may be the first to do a real-world experiment, which would involve launching a balloon into the stratosphere, releasing a small amount of calcium carbonate, and then measure how light scatters and changes in atmospheric chemistry. The team was interested in conducting the experiment this year, but will not move forward without the recommendation of an independent, independent advisory committee that is creating it. "To us, the governance of this is equally as important as the scientific goals for the experiment," says Burns.
One of the fundamental questions of solar geoengineering is who gets to decide if it happens: For an action that affects the the whole planet, who has that right? The actual process may be inexpensive enough (by one estimate, less than $ 10 billion a year) that there is a risk that a single country might decide to act unilaterally. That's part of the reason why research is so critical; "If the international community is confronted with impacts of climate change that are severe or more severe than expected, when people are then talking about available tools, we need a better understanding of what solar geoengineering may or may not be able to do, "says Burns. "In our view, it's not saying that we need it. If anything, I hope you do not need it. It's a very scary technology. It's quite terrifying. But the world with severe climate change impacts can also be very scary. "