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There are tons of reasons not to rely on sun blocking to cool the planet. But a new paper presents perhaps the best so far: it may not work if we continue to let carbon emissions skyrocket.
The findings, published Monday in the Proceedings of the National Academy of Sciences, are based on models made last year that showed that we could face a heat death from cloud loss if world leaders let carbon pollution continue. to increase. The same group of scientists used the same modeling approach to see what would happen with increased emissions, but the world comes together to reflect sunlight back into space. The study comes with some caveats, but it’s an important thought experiment as we try to understand the intricacies of the climate system and how our choices might affect it.
The process, known as solar radiation management, is something that is increasingly scrutinized by researchers as world leaders fail to cope with the climate crisis. It involves injecting tiny particles high into the atmosphere to send the sun’s energy into space. Less incoming solar radiation would mean less energy trapped near the Earth’s surface, which would mean it’s less hot for all of us. But blocking the sun could pose a number of other problems, from negative impacts on crop productivity to changes in rainfall to not being able to stop it.
The new paper examines how blocking the sun even as emissions rise would impact stratocumulus clouds in the tropics. Those clouds have reflective tops and vents for outgoing energy. In other words, they act as a key cooling force. But previous research has shown that they likely taper off and become less common as the planet warms, although speed is an active research area. The new research uses a model that shows that they thin out and then suddenly dissipate at very high concentrations of carbon dioxide in the atmosphere. But the researchers introduced a new component into their model to see if managing solar radiation could save clouds and, by extension, the world.
The results show that even with efforts to block the sun, clouds slowly thin out and surface temperatures rise. But the real shock to the system comes when carbon dioxide levels reach an extreme of around 1,800 parts per million (ppm): at which point, the clouds vanish and rapid warming ensues, due to an increasingly opaque atmosphere. clogged with carbon dioxide and water vapor. The change is stark, with temperatures ranging from a few degree warming increase to a sudden jump of 7 degrees Celsius.
If it sounds bad, well, it is. But let’s allow me and Kate Marvel, a NASA and Columbia University scientist who studies clouds (and, to full disclosure, she is my colleague at Columbia), to bring you back from the ledge.
“The models allow us to do ‘experiments’ that never would have happened in the real world to try and learn about complex systems,” he said in an email. “This is an example of that. It should by no means be taken as a realistic representation of what would actually happen in any real-world geoengineering scenario, and the authors are very explicit about it. “
Indeed, the research is a what-if novel to look at a vital but little-studied part of the atmosphere. Clouds are everywhere and have many different tastes, yet climate scientists are still working to unravel their impact on the climate and, in turn, our impact on them. While tropical stratocumulus have a cooling influence, for example, cirrus clouds can warm the planet. We have a lot to learn on this front and understanding clouds and how geoengineering can interact with them is something we should be researching.
There is also the fact that the carbon dioxide concentrations at which clouds disappear are extreme (or as Marvel put it, “BANANAS”). We currently live in a 410 ppm world and it took about 170 years to get here from pre-industrial levels of around 280 ppm. Yes, the slope of the curve has increased. But the problem of climate change has also become more urgent, and while it’s certainly possible that the world will go to cities and burn dead dinosaurs still underground, such a path seems less likely. Even if we decide to do so, concerns about the functioning of our sunlight reflection strategy will almost certainly be the least of our concerns.
“This document does not say ‘geoengineering will eliminate the clouds, everyone will be panicking,'” Marvel said. “He’s saying, ‘hey, here’s yet another aspect of the earth system that’s complicated; we put a lot more effort into studying this before doing something rash. “
Which one, yes. Additionally, we consider reducing emissions quickly before we start testing these models in real life.
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