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If you think that pumping a sky filled with chemicals is a strange way to fight climate change, you are not alone. Solar geoengineering – the idea of injecting aerosols into the upper atmosphere to reflect sunlight in space and create a colder planet – is highly controversial. And not only because it seems so offbeat.
Although geoengineering is not yet deployed in the real world, previous computer modeling studies have shown that it could produce unexpected effects such as droughts. Some have feared that this will create new climate inequalities, worsening weather conditions in some areas and improving conditions in others. The backlash is so important that until recently it was a taboo subject for scientists, and even today there is much less focus on exploring this strategy than reducing emissions.
But a study published this week in Nature Climate change argues that the strategy could be successful – it's all about how much we use geoengineering. Yes, spraying huge amounts of aerosols to completely eliminate global warming can have undesirable effects. Still, applying the "right" dose – just enough to reduce global warming by half – could do the trick without causing any negative side effects, according to the scientists.
"The analogy is not perfect, but solar geoengineering is a bit like a medication treating high blood pressure," said lead author Peter Irvine of "The best of the world. Harvard University. "An overdose would be harmful, but a well chosen dose could reduce your risk."
In this study, Irvine and her co-authors used a high-resolution computer model to simulate what would happen if we deployed geoengineering to halve global warming, in a scenario where carbon dioxide levels our atmosphere has doubled compared to pre-industrial levels. (At present, we are about 1.4 times higher than previous levels.) While most previous research focused only on temperature and precipitation, this study also looked at other important aspects of climate change. people, such as the availability of water.
The results? Geoengineering has cooled the planet and reduced the intensity of extreme weather events such as hurricanes. Importantly, this has been true around the world. There were no regional winners and losers, only winners. The researchers noted that the regions that suffered the most from climate change were the most likely to see it reduced.
Critics of geoengineering fear that while this may benefit the rich, it may be detrimental to low-income people who may be less equipped to cope with unexpected weather changes if things go wrong and will not have as much voice in deployment. But David Keith, lead author of the study and professor of physics at Harvard, said he thought it would be a net benefit for people with low incomes.
"The poorest people tend to suffer more from climate change because they are the most vulnerable. Reducing extreme weather conditions benefits the most vulnerable. The only reason I'm interested is for that, "he said.
The study has significant limitations
Do not be too excited for now. The study – a collaboration between Harvard, MIT and Princeton – is based on a highly idealized scenario.
The researchers chose to use a scenario in which CO2 levels in the atmosphere doubled from pre-industrial levels at the time of geoengineering deployment. "Double" may seem like a lot, but some climate scientists think that our CO2 levels will be terribly higher than that by the middle of this century. And we are not even on the verge of being ready for a large-scale program. deployment of geoengineering. So, using this scenario, the study can prepare for an unrealistic and optimistic result.
It is also important to note that the study does not model what happens when you launch aerosols into the sky. It models what happens if the sun's rays are attenuated. Alan Robock, an expert in climate science at Rutgers University, argues that he does not accurately capture the impact of aerosol spraying, which could have other effects, such as a disruption of atmospheric circulation.
The study team agrees that aerosol modeling is also important, but that asking one model to do everything is not necessarily the best option, according to Keith. "Climate models treat aerosols very poorly, so it's not clear that you can trust the results. In our opinion, it makes more sense to use this model, then to make models that have very good representations of aerosols separately. It's like building a bridge on two sides, "he told me.
The findings of the study are far from certain enough that decision-makers should make informed decisions – the researchers themselves are the first to point this out. For example, even though the model indicated that no region would be worse off with geoengineering than without it, Keith said, "I think if it happens in the real world, some areas or activities will be less well-off. Because nothing in the real world is safe. "
"I think it would be ridiculous to deploy such a project as long as a much broader and more open international research effort – with research groups specifically focused on critical ideas – and only after an adequate system of governance has been achieved. been put in place. "
Explaining why he wants other researchers to test his group's ideas, Keith has shown an unusual frankness for a scientist discussing controversial new work. "I think there is a real risk of thinking in a group at this stage, but with such a small number of researchers, including myself. [studying geoengineering]. We could just be deceived. "
Why are people so worried about geoengineering?
Solar geoengineering is an idea of interference in nature that stems from the observation of nature itself. As my colleague Dylan Matthews detailed in a podcast episode, scientists came up with this idea by observing volcanoes. They noticed that when volcanic eruptions threw sulfur particles into the sky, they temporarily caused a reduction in temperatures on the Earth. They began to wonder: what would happen if we basically imitated the impact of volcanoes?
Their detractors, however, seem to think that nature sprays chemicals in the sky is one thing, but the humans who do it deliberately are another story.
In a recent article titled "Geoengineering Justice," Jonathan Symons, senior lecturer in international relations at Macquarie University, hypothesizes that "the prohibition of intentional interference in nature – a standard determinant of modern environmentalism – discourages any discussion of the potential benefits of solar geo-engineering. " He explains:
In its expansive history The Progressive Prometheans of the Environment, William Meyer traces the roots of this ban. For centuries, Promethean belief in man's ability to improve his biophysical environment was primarily associated with the political left. With the advent of modern environmentalism in the 1960s, this progressive prometheanism was reversed. The Greens have now underlined the "danger of undesirable consequences resulting from interference in the complex system of nature". As a result, Prometheanism has been associated with conservative opponents of the environmental movement.
This sociological perspective partly explains why scientists supporting geoengineering experienced such a reaction.
"What [critics] I think sometimes they implicitly say they prefer not to see the research, "said Keith. "Yes, there is some kind of research that we should be doing away with – like making a small pox in your basement – but I think the case for the suppression of research in this case is rather weak. show that geoengineering could significantly reduce the risk to the environment. "
In addition to worrying (very legitimately) about security issues that could result from imprudent deployment of geoengineering, critics also fear that research on this subject will accidentally provoke complacency about the reduction shows.
Whether we use geoengineering or not, we absolutely have to reduce our emissions, otherwise we will continue to aggravate the climate crisis. But reducing emissions does not solve the problem of CO2 already present in the air. This is why scientists are proposing geoengineering as a complement to reducing emissions, not as a substitute.
Keith himself worries about the risks of complacency. "I am very concerned that companies and other entities with interests are exploiting the work we are doing to combat emissions reductions – Big Fossil will not make an excessive claim as to how geo-solar engineering will be available one day, "he said. "On the other hand, I do not think it means they will win. And I do not think that's a reason for not doing research on this. "
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