An international group of scientists led by Cornell is, more rigorously and systematically than ever before, assessing whether and how the stratosphere could be made a little “brighter,” reflecting more incoming sunlight for an increasingly warming Earth stay fresh
Their work was published Aug. 12 in the Proceedings of the National Academy of Sciences.
Solar radiation modification, or solar geoengineering as it is sometimes called, is a potential climate change mitigation strategy that involves injecting sulfate aerosols into the stratosphere so that more sunlight bounces back into Earth’s atmosphere. Along with other strategies, such as reducing greenhouse gas emissions, this could help prevent the planet’s temperature from rising too much.
“Even if we act aggressively on climate change, it’s still going to get worse,” said lead author Doug MacMartin, principal investigator and professor in the College of Engineering and professor at the Cornell Atkinson Center for Sustainability. “We face difficult decisions in the coming decades about whether or not to complement other climate change mitigation strategies with methods to reflect sunlight.”
While cooling the climate with the help of a known pollutant could reduce some of the impacts of climate change, it would also have other effects, from changes in precipitation to acid rain, leading to trade-offs that are not yet clear.
There would also be significant challenges in terms of how the world would make decisions about deployment. A more systematic assessment of these trade-offs, comparing the impacts associated with a range of different options, could inform these decisions.
“Anyone who hasn’t heard of this strategy before, the first reaction should be ‘Wow, you can’t be serious.’ That sounds horrible,” MacMartin said. “And maybe it is, but climate change isn’t good either. Maybe we’re past the point of easy solutions. If we want to be able to provide future decision makers with the best possible information, we need to compare the risks of ‘use this technology with the risks of not using it’.
In the paper, the scientists list several scenarios that explore different options and present new climate model simulation results. These scenarios assume that deployment could begin in 2035, and the effects of this choice are assessed against a start date a decade later. Other scenarios explore risks such as abrupt termination or temporary interruptions.
MacMartin said this framework represents a significant step forward from previously conducted simulations that were not always deliberately designed to inform future policy and typically only simulated a single future pathway.
The modification of solar radiation is still theoretical, he said. To begin with, a small fleet of specialized high-flying aircraft would be required, and none currently exist with the ability to deliver an adequate payload of sulfur dioxide, which would naturally convert to sulfate aerosols, at a high enough altitude high
However, the approach is not entirely new either. During Earth’s long geological history, volcanic eruptions have occasionally released sulfate aerosols into the stratosphere, cooling the planet.
“In that sense, we’re not talking about introducing something completely unnatural,” MacMartin said.
In addition to MacMartin, co-authors of the paper, “Scenarios for Modeling Solar Radiation Modification,” are research associate Daniele Visioni; PhD student Walker Lee; Ben Kravitz, Indiana University; Yaga Richter, National Center for Atmospheric Research; Tyler Felgenhauer, Duke University; David Morrow, American University; Edward Parson, University of California, Los Angeles; and Masahiro Sugiyama, University of Tokyo, Japan.
Cornell Atkinson and the National Science Foundation supported this research.
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