Harvard scientists plan first field experiment in connection with solar geoengineering


In June 1991, Mount Pinatubo erupted in the Philippines. It was the second largest volcanic event of the century. Hot ash shot 22 miles to the sky.

The ashes spat out 20 million Tons of sulfur dioxide into the stratosphere. This gas formed a kind of protective shield around the earth that reflected sunlight back into space. The reduction in the amount of sunlight shining on the earth caused the planet to cool for two years. The temperature dropped by 0.5 degrees Celsius – a sharp drop in terms of the climate.

Scientists have long wondered if humans could do something like this on purpose – cool the earth by injecting a substance into the stratosphere, the second layer of the atmosphere. The controversial technology called “Solar Geoengineering” could be used by humans to change the climate in a targeted manner.

“They would reflect a little sunlight away, just as a very thin cloud reflects a little sunlight … to offset some of the warming caused by the slow build-up of carbon dioxide from our industrial activity,” says David Keith, professor of applied physics at the Harvard University.

For a long time, research into solar geoengineering was taboo. It’s a powerful technology with the potential to change the atmosphere, climate and human health.

But with the climate change weighing on us some Researcher venture into science.

Keith and Harvard Professor of Atmospheric Chemistry, Frank Keutsch, are planning a first field experiment of its kind to help scientists understand the effectiveness and risks of solar geoengineering. You plan to release an aerosol – less than 2 kilograms of calcium carbonate – into a tiny part of the stratosphere to see how it behaves.

However, Keith and Keutsch are currently working in a laboratory at Harvard. There, a large part of their attention is directed to a metal tube about one meter long and a few centimeters wide that acts as a mini-stratosphere. They carry out experiments in the tube, similar to what they want to do high above the earth.

Professors David Keith and Frank Keutsch in their laboratory at Harvard University. (Robin Lubbock / WBUR)

“So we’re going to stratospheric temperatures. We go in there at stratospheric pressures, ”explains Keutsch. “We enter the aerosol whose reactivity we want to understand. And then we look at these reactions [in the tube]. “

This aerosol – calcium carbonate – is the same compound found in limestone and mussels. It’s found in common consumer products like toothpaste and antacids. Calcium carbonate isn’t in the stratosphere – but one day humans could spray enough of it to reflect the sun.

In the Harvard experiment, however, the scientists want to measure how the compound interacts with gases in the stratosphere. This could help determine whether it would further damage the ozone layer.

David Keith says their plan is to launch a scientific balloon, likely in the American Southwest.

“The balloon is about a few stories in diameter, and these are the same stratospheric balloons that have long been used in science,” he says.

It would soar 12 miles – twice as high as a passenger plane goes. Keutsch explains that a metal gondola with propellers would hang from the balloon.

“This nacelle has a mechanism with which particles can be injected into the stratosphere,” says Keutsch. “So when you move around, you make a cloud that’s about a kilometer long, a few kilometers long. Then you would try turning the balloon over and pulling a sample back through that cloud to compare how the air outside the cloud is different from the air and the aerosol in the cloud. “

Your project is called SCoPEx – Abbreviation for Stratosphere Controlled Perturbation Experiment.

Harvard scientists insist that the experiment itself is not solar geoengineering; They say it is too humble to affect the climate and it is safe. Others disagree.

“Once you start bringing particles into the stratosphere, aren’t you interfering with the climate?” asks Daniel Cziczo, the department head of Earth, Atmospheric and Planetary Sciences at Purdue University. For most of the past decade, he has taught at MIT.

Cziczo says the SCoPEx project fits into what he calls “climate intervention” rather than solar geoengineering, and he says science is dangerous.

“Even though you say, ‘I’m doing it as an experiment,’ the result is exactly the same,” he says. “It could be on a smaller scale … but I would argue that if you put enough material in there, you will look at the properties of that material and try to tell what effect it has on what you are” redoing is an experiment for climate intervention. “

Cziczo says comprehensive climate intervention would disrupt cloud formation, further damage the ozone layer, and do nothing to reduce carbon in the atmosphere.

“I’m not ready to sign up for something that has a solution for that [earth’s] Temperature problem that will cause more skin cancer, that will allow ocean acidification to persist, or cause regional droughts or rainfall, “says Cziczo, another avenue in climate – and that is reducing those greenhouse gases, which we know are the underlying cause . “

The three scientists agree: The real solution to global warming is to reduce fossil fuels. They are concerned that people will see solar geoengineering as an easy task; they call this the “moral hazard” of science.

“This experiment can be so misinterpreted that there is a technical cure that will throw us off balance, although it should be clear that … even in the best case, solar geoengineering in the stratosphere does not address the causes of climate change” , explains Keutsch. “It’s about a symptom.”

David Keith is concerned that the energy industry is shirking its responsibility to reduce global warming.

“I’m talking about big oil companies, big fossil fuel companies – that they’re going to claim that because of this technological solution, there is no need to cut emissions. That’s not true, ”says Keith. “Nothing about solar geoengineering changes the fact that you have to reduce emissions to zero at some point if you want a stable climate.”

Keith sees promising opportunities in solar geoengineering.

“Nothing about solar geoengineering changes the fact that you have to reduce emissions to zero at some point if you want a stable climate.”

“The combination of emissions reductions and solar geoengineering could actually be significantly safer, have lower risks for humans and the environment, less sea level rise, fewer people die from heat stroke, have fewer changes in the high arctic glaciers than a world with only emissions reductions,” he says. “So there really is a price here, an enormous benefit for people and the environment.”

But the scientific community needs to research the consequences – good and bad, Keith says – before leaders make hasty decisions.

“Some governments, potentially facing a major, fatal heat wave, may make decisions to actually deploy these technologies within the next few decades, regardless of what research we do,” says Keith. “We’re more likely to make an informed choice as a species, as a human race, if we get it public, warts and everything.”

There is no national or international management structure for solar geoengineering. The proposed SCoPEx experiment can finally be checked by the federal government within the framework of national regulatory laws Environmental policy and Weather change.

Harvard has one independent committee Review and make recommendations on all aspects of the experiment, including its safety and environmental impact.

Meanwhile, the coronavirus pandemic kept David Keith and Frank Keutsch away from their lab for a few months. They are now back and working towards the day they will get the green light to launch their big balloon.


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