We could spray cheap chemicals in the air to slow climate change. Should we?


The Earth continues to heat up. Mankind is actually not enough to stop it. Scientists are therefore increasingly thinking of taking spectacular actions in the atmosphere to cool the planet. And new research suggests that an atmospheric cooling project would not only be feasible, but also cheap enough for only one specific country to achieve. This cooling would not reverse climate change. The greenhouse gases would still be there. The planet would continue to warm up overall, but this warming would slow considerably, measurably.

These are the findings of an article published November 23 in the journal Environmental Research Letters by two researchers from Harvard and Yale Universities. This is the deepest and most recent study on "aerosol injection into the stratosphere (also known as" solar gradation "or" solar engineering "). This is the spraying of chemicals into the atmosphere to reflect the heat of the sun in space, mimicking the overall cooling effects of large volcanic eruptions.

The researchers discovered that humanity could, by using this method, halve our species' annual contributions to the greenhouse effect at a price that states and big cities spend all their time on building highways. , metros and other infrastructure projects: $ 3.5 billion in total. over the next 15 years to develop the technology. (Most of these funds would go towards building planes capable of carrying large aerosol reservoirs into the stratosphere, about double the cruise altitude of a Boeing 747. Once the technology is ready, the researchers discovered that the project would cost $ 2.25 more. billion euros each subsequent year (assuming that the effort will run over the next 15 years).

By comparison, the Massachusetts Department of Transportation's budget in 2017 was $ 1.8 billion. Texas will have spent nearly a billion dollars to replace a single bridge in Corpus Christi. Metro repair budgets in New York are typically tens of billions of dollars. Belgium spends about $ 4 billion a year on military forces. In other words, the geo-engineering of the atmosphere to slow down climate change is cheap enough that a small state or country can probably afford to do it, not to mention a superpower like the United States or China. [8 Ways Global Warming Is Already Changing the World]

It may seem crazy, but researchers outside the newspaper said his methods were sound and that his conclusions were not so surprising.

"[The paper] Kate Ricke, a professor at the University of California at San Diego, who studies climate change and the policies to deal with it, seems reasonable and methodical. "I think it's a useful contribution because it confirms the idea that the engineering stratosphere would be much cheaper than the emission reductions for the same global temperature effect."

Ken Caldeira, Senior Scientist at the Carnegie Institution for Science, agrees.

"We could expect cost overruns in all government operations, but overall, I have no reason to question these conclusions, they seem reasonable to me", a- he told Live Science.

The science here is in some simple respect: Unload sulfur dioxide (SO2) into the atmosphere and it will reflect light into space. SO2 is cheap and there are many. Wake Smith, co-author of the paper and speaker at Yale, said most project costs would come from increasing SO2. [Cool the Planet? Geoengineering Is Easier Said Than Done]

"If you deploy hardware at 35,000 feet [10,700 meters]Let's say that where your 737 is flying, it's raining in a few days, because gravity is simply acting on it, "he told Live Science. If you ride it in the stratosphere, it stays at altitude for a year or 18 months. "

(This is one of the reasons why the chemtrail conspiracy theories, which mistakenly link chemtrails to a secret government plan to change the weather, are so implausible, he added. week.)

Nevertheless, it is clear that achieving a sufficiently high SO2 is not an insurmountable challenge, and this approach could really cool the planet.

But cooling the planet is not the same as reversing climate change, the researchers said.

Carbon emissions do more than just form a chemical greenhouse around the planet. They also make the oceans more acidic and alter the overall movement of air and water. Already, these emissions fueled the system in heat that would not disappear if humanity projected a layer of SO2 in the stratosphere.[[[[The craziest solutions to climate change]

"We may be able to reduce overall surface temperatures globally, compared to what they would be in a world without engineering," Smith said, "but that does not mean the climate of all places will come back In the opposite direction, some places will be warmer, others colder, others drier, others even wetter, and even a perfectly arranged climatic future, which is impossible, will change. things all over the world, and that will not change to be good for people either. "

In addition, he added, climate change has tipping points that a SO2 dressing would not fix.

"If all the ice in Greenland melted and slid into the sea," said Smith, referring to a scenario that would dramatically increase sea levels and flood the shores of the world, "and then refreeze the planet or cool it down technically ., the ice will not rise from the sea to the land.The ice of Greenland is the result of millions of years of snow. "

So even though he thinks this type of geoengineering deserves to be studied, he said it was important that people understand that this was not a solution.

"I'm afraid some fossil fuel companies are saying exactly that, and the geoengineering community will have to find a way to guard against this infiltration or any other association in the public mind," he said. .

The idea of ​​pumping aerosols into the upper atmosphere in order to mitigate climate change has been taken seriously enough for this concept to have appeared in the recent IPCC 2018 report on climate change as a 39 possible mitigation approach – although the IPCC has not approved this type of spraying. For now, it seems cheaper than alternative geoengineering technologies, said Ricke, as proposals to suck carbon dioxide out of the atmosphere. (The Intergovernmental Panel on Climate Change (IPCC) is an international organization established by the United Nations to assess the science, risks and impacts of climate change.)

But that does not mean that such approaches will, or should, happen, all researchers agreed.

"I do not think it's a good idea at the moment," Ricke said. "I do not think we know enough about how to do it, and we do not have a system to reach an agreement on how much we should be doing or how we are going to do it. should make this decision regarding the details of where we would place more aerosols, etc. I do not think we are close to each other. "

But all this could change, she said.

"There are many frightening effects on climate change, such as the melting of glaciers in Greenland and Antarctica, which are facing us," she said. "Because [cutting emissions] and the elimination of CO2 will take some time, even though we are serious about implementing them – which I am not convinced – I think solar geoengineering has the potential to be one of the only remaining options. "

According to Mr. Smith, this is troubling for several reasons, one of them being that there would almost certainly be some side effects that the sprayers could not anticipate. One of the benefits of spraying, he added, is that as soon as it is stopped, its effects will disappear within 18 months.

Caldeira acknowledged that the use of such engineering seemed more and more likely, but doubted that this would happen, because of the political dynamics involved. No politician, he said, would want to be held responsible for a meteorological event that occurred in the year following the adoption of the SO2 vote.

"Imagine if Hurricane Sandy occurred the year after the start of the establishment of this material," he said, suggesting that people could blame the atmospheric engineering.

Nevertheless, he added, a small country severely affected by climate change may decide to do so without overall approval. However, the paper notes that such an effort would be impossible to keep secret, and that other major nations might decide to stop the project. Performing this job properly would require flying over the middle latitudes of the world, and this should continue indefinitely. (Unlike sulfates, masking the warming effect of greenhouse gases does not make them go away and they can last a thousand years in the atmosphere.Solar engineering should therefore continue to thwart these effects.)

"I will not say if [I think we’ll get to the point of atmospheric spraying], "Smith said," not because it's too much of a hot potato, but because I do not really know. "

Other geoengineering techniques may become cheaper, or countries may never resort to this type of climate mitigation, he said.

For the moment, Ricke said, the big outstanding questions are about the chemistry of the stratosphere – how would sulfur interact with other chemicals in the atmosphere – and the local effects of this type of program? . How would a new large batch of SO2 in the atmosphere affect the ozone layer, for example? How would regions, agriculture or local water systems react to the sudden change in sunlight? How would the public react?

For now, she says, she wants to see a lot more research.

Originally published on Science live.


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