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Solar geoengineering could have big benefits (and also big risks)

A new study found the effects on inequality from lowering global temperature via limiting the sun that reaches the Earth could be massive. But can we get those same effects simply by reducing carbon emissions in a less risky way?

Solar geoengineering could have big benefits (and also big risks)
[Illustration: FC]

Climate change has made the world more unequal. As the planet has warmed, poor countries have gotten poorer while some rich countries got richer, and that disparity is expected to only increase as temperatures do. But reversing climate change could help mitigate those disparities, a new study has found.

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The study, from University of California San Diego, is specifically interested in one controversial method of achieving that reversal: solar geoengineering. The researchers say that not only could the technology mitigate climate change, it could also help developing countries catch up economically, making the world a bit more equitable.

Solar geoengineering is the intentional reflection of sunlight away from the Earth’s surface, which works to cool down the planet. It’s an area of emerging research and technology, and experts have proposed a few ways to carry it out. One is through marine cloud brightening, which involves spraying salt water into the air to make clouds whiter and brighter so they are more reflective, thus preventing as much sunlight from reaching the Earth. Another option is stratospheric aerosol injection, which would mirror the cooling effect of volcanic eruptions by spraying water particles into the atmosphere and then injecting those particles with sulfate aerosols, which include sulfuric acid and are part of a volcano’s explosion. Just as brightly colored roofs and streets reflect sunlight, and therefore mitigate the urban heat island effect, this reflection of sunlight on a grand scale could cool down our planet.

Researchers (at Harvard, the University of Washington, and UCLA’s Emmett Institute on Climate Change and the Environment, to name a few) are all exploring solar geoengineering as a climate solution, but they’ve been focused on the physical aspects of the technology. Researchers at the University of California San Diego wanted to look at the economic and policy-related impacts. Their study, published in Nature Communications, modeled the socioeconomic impacts of four future scenarios: if no further climate change happens and we stay at current temperatures; if global temperatures continue to rise; if temperatures were stabilized through solar geoengineering despite increased greenhouse gas emissions; and if global temperatures were overcooled, dropping around 3.5ºC, by solar geoengineering.

“For both scenarios with solar geoengineering, what we find is that we have this result of inter-country inequality—so the inequality between countries—being reduced . . . relative to that warming scenario,” says lead study author Anthony Harding. Economic gains seem to be the strongest for developing tropical countries, such as Niger, Chad, and Mali—each of which saw a more than 100% increase in average incomes over the course of a century in the model that projected a solar geoengineered-decrease in average global temperatures. In that same model, the United States and countries in Southern Europe saw a more modest income increase of around 20%.

Countries saw different economic impacts under each model, but the researchers say that changes in temperature associated with solar geoengineering consistently translated to a 50% drop in global income inequality.

It’s not exactly clear to Harding and the other researchers what’s driving that change in inequality, especially for those tropical, developing countries. “These countries seem to be most harshly affected by climate change, and kind of inversely seem to benefit the most from solar geoengineering,” Harding says. “The economic gains seem to be strongest for the developing tropical countries, which kind of help them catch up to the initially more developed economies.”

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Solar geoengineering isn’t the only way to stabilize temperatures and mitigate climate change, and Harding speculates that based on these findings, any mitigation effort that reduces global temperatures would also reduce this intercountry inequality. But the implications of solar geoengineering haven’t been quantified before so the researchers wanted to model the effect. Also, while other mitigation efforts, such as reducing carbon emissions, require global agreements (the Paris Accord, for example), it’s not necessary for everyone to work together to see the benefits of solar engineering. If one country, or person, had the money and means to carry this out, we could potentially see temperatures drop on a global scale. That’s why this could be crucial in terms of climate-related inequalities, and why, Harding says, “putting strong efforts into a global governance structure is important.”

That same factor of unilateral action, though, is just one of many criticisms against solar geoengineering. It’s been criticized because one country could have such power to affect the world in this way, and because of the costs associated with these efforts, which would be “remarkably expensive,” and could be better spent on existing climate mitigation efforts that we are already sure would work, without the same risks. Another point critics make is that solar geoengineering doesn’t address the root cause of climate change: our high fossil fuel emissions.

Because there is currently no global governance structure for solar geoengineering, no one knows what its actual implementation should, or could, look like—and that leaves open the question of who then will have their hand “on the global thermostat” if it comes to fruition. As research into this technology continues, we need to have these economic and ethical implications in mind, Harding says. The technology may not be ready to deploy, but if it ever is, we need to be ready to address all the implications and even control how it may be used, so one country doesn’t have the only say. “We really need to start seriously thinking,” Harding says, “about how we might design policy around solar geoengineering.”

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