At this point in the climate crisis, the need to cut carbon emissions is repeated like a mantra. The goal is to prevent the world from warming further, but in a scenario where emissions continue to increase and temperature records are broken every year, some scientists are proposing a controversial idea: what if the planet could be artificially cooled? This is what solar geoengineering proposes. The best-known of its promoters, the American David Keith (Madison, Wisconsin, 60 years old), does not believe that it is a magic solution or an alternative to cutting emissions, but rather a “necessary conversation.” The proposal is, on the surface, simple: release sulfuric acid into the atmosphere so that it reflects sunlight and lowers temperatures.
Keith is a professor in the Department of Geophysical Sciences at the University of Chicago, where he has a team dedicated to solar geoengineering research. He was previously a professor of Applied Physics at Harvard University and, in 2009, was inducted by the magazine Time on the list of Environmental HeroesIn 2013, he also published the book A Case for Climate Geoengineering (An Argument for Climate Geoengineering, not published in Spanish).
The physicist has been writing about solar geoengineering since 1992, although he explains his interest in the subject without a hint of romanticism. “I studied physics and did a postgraduate degree at the Massachusetts Institute of Technology, but I was looking to do something that was more environmental, and I found a network of people who were researching climate change, a subject that no one was working on at the time, so I got down to it,” he explains to EL PAÍS via video call from Chicago.
The idea of solar geoengineering seeks to imitate the effect of volcanic eruptions, which shoot sulfur dioxide into the atmosphere. When it reaches the stratosphere, it turns into sulfuric acid and accumulates until it functions as a reflector. According to author Jeff Goodell in his book The Heat Will Kill You First: Life and Death on a Scorched Planet (not translated into English), when the Pinatubo volcano erupted in the Philippines in 1991, it released 15 million tons of sulfuric acid into the atmosphere and lowered temperatures in the region by about one degree Celsius for a year. Solar geoengineering aims to recreate a similar effect on a planetary scale using aerosols that place the same substance all over the globe.
They are called stratospheric aerosols, small particles that reflect solar radiation, such as sulfuric acid. These can reach the stratosphere naturally, as in volcanic eruptions, but in solar geoengineering the proposal is to artificially inject them to reduce global warming.
Pollution and temperature
Keith is careful with his words when talking about his work and does not deny the risks of this experimental method: “Sulphuric acid is an air pollutant, probably the most important in terms of impact on humans. It kills millions of people a year, so it is an obvious risk. There is also the risk of damaging the ozone layer.”
But even with these dangers, the physicist maintains that the benefits could be greater. “Although there are uncertainties, there is a broad consensus, even among the most critical, that stratospheric aerosols would reduce temperatures everywhere. And the benefits of temperature reduction are greater, especially in the hottest countries and for poor people. For me, if there is one ethical reason to take this technology seriously, it is that,” he says.
For Keith, there are benefits and risks to “almost any intervention” that humans make, which should not be an argument for not doing something. “For example, solar energy is fantastic, the most important thing that has happened in the world of energy, but it also has environmental damages. There are risks of toxic metals in the production chain. These are real things and we should work on them, but it is not a reason not to use solar energy,” he says.
“The first high-quality paper on stratospheric aerosols is from 1960. So we know a lot. Thousands of papers have been written over a long time. We don’t necessarily have the hardware, but we do have the technological capability to do it. So what we can do is compare how much cooling would reduce heat deaths, and we can compare that to deaths from air pollution,” Keith says.
In a recent article by The New York Times on solar geoengineering In addition to Keith’s work, the paper cites several critics of the science. Environmentalist David Suzuki, for example, called the idea of releasing sulfuric acid into the atmosphere “arrogant and simplistic.” The article mentions that solar geoengineering entails consequences that are not even understood, as well as the danger that the world will embrace these solutions over emissions cuts because they are more convenient for polluting industries. Keith, however, is clear that he does not believe solar geoengineering is a substitute for other environmental efforts.
Another criticism of solar geoengineering is the frequency with which the aerosols would have to be applied, because sulfuric acid only stays in the stratosphere for about two years. For Keith, however, that is a good thing, because the aerosols could be applied gradually and, if the results are not as expected, they could be stopped or adjustments made. “That is a good thing. If you put sulfuric acid on and then it stayed there forever and you couldn’t remove it, you would be permanently changing the climate,” he explains.
Thinking in four dimensions
According to the scientist, there are four ways in which humans can manage climate risk: reducing emissions, removing carbon from the atmosphere, solar geoengineering and, finally, adaptation methods. “We have to think in four dimensions,” he says.
In addition to solar geoengineering, the physicist has also worked with the second method, carbon removal. In 2009, Keith founded Carbon Engineering, a company that specializes in a process for extracting carbon dioxide from the atmosphere. This technique is known as air capture, and some oil companies have begun using it to try to reduce their gigantic environmental footprint. Among Carbon Engineering’s initial investors was the oil company Chevron. Last year, the company was acquired by Occidental Petroleum, another Texas-based oil company that has made air extraction its flagship, for a total of $1.1 billion.
Keith no longer has any ties to Carbon Engineering and avoids the topic altogether when asked if he still “promotes” carbon extraction as a viable alternative for the environment. In his statements to The New York TimesHe said, however, that he was “not comfortable” with the company being acquired by an oil company and that he was considering donating the money he received to a conservation group.
Despite no longer being involved in any carbon removal initiatives, Keith believes that this method should be talked about as much as solar geoengineering and adaptation. “A long time ago, people like Al Gore said that we shouldn’t talk about adaptation because it would be immoral to divert attention from reducing emissions. But I think most people would now agree that, in fact, Gore’s own statement was immoral. People in Bangladesh have a right to try to protect themselves from the harmful effects of climate pollution. That’s why there’s a lot more attention now on adaptation.” Keith believes that this interest will also gradually extend to carbon removal and solar geoengineering.
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