David Keith was a graduate student in 1991 when a volcano erupted in the Philippines, sending a cloud of ash toward the edge of space.
Sulfur dioxide spewed from Mount Pinatubo spread through the stratosphere and reflected some of the sun’s energy back toward Earth. As a result, average temperatures in the Northern Hemisphere dropped by about 1 degree Fahrenheit (0.556 degrees Celsius) the following year.
Today, Keith cites that event to validate an idea that has become his life’s work: He believes it might be possible to lower temperatures around the world by intentionally releasing sulfur dioxide into the stratosphere.
Such radical interventions are being considered more seriously now that the effects of climate change are intensifying. Global temperatures have hit record highs for 13 consecutive months. Scientists expect the heat to continue to rise for decades. The main driver of warming, the burning of fossil fuels, continues almost unabated.
In this context, there is growing interest in projects that aim to intentionally alter the Earth’s climate, a discipline known as geoengineering.
Some of the biggest companies already operate huge facilities dedicated to sucking up atmosphere-warming carbon dioxide and burying it underground. Some scientists are running experiments designed to make clouds brighter, another strategy to reflect some of the sun’s radiation back into space. Others are working on projects that aim to make oceans and plants absorb more carbon dioxide.
But of all these ideas, stratospheric solar geoengineering is the one that generates the most hope and also the most fear.
Advocates see it as a relatively cheap and quick option for lowering temperatures long before the world stops burning fossil fuels. Harvard University has a solar geoengineering program that has received funding from Microsoft co-founder Bill Gates, the Alfred P. Sloan Foundation and the William and Flora Hewlett Foundation. It is being studied by the Environmental Defense Fund in conjunction with the World Climate Research Program. The European Union said last year that countries should hold talks to determine how to regulate the technology when the time comes.
But many scientists and environmentalists fear it could lead to unpredictable calamities.
Because it would be used in the stratosphere and not limited to a particular area, solar geoengineering could affect the entire world and even cause disruption to natural systems—for example, it could create rain in an arid region or dry out the monsoon season elsewhere. Opponents worry that such projects will distract from the urgent work of transitioning to a world without fossil fuels. They object to the release of sulfur dioxide, a pollutant that would then travel from the stratosphere to ground level, where it can irritate skin, eyes, nose and throat and cause respiratory problems. And they fear that once a solar geoengineering program gets underway, it will be difficult to stop.
“The notion of spraying sulfur compounds to reflect sunlight is arrogant and simplistic,” said Canadian environmentalist David Suzuki. “These powerful technologies have unintended consequences, and we have no idea what they will be.”
Raymond Pierrehumbert, an atmospheric physicist at Oxford University, said he considers solar geoengineering a serious threat to human civilization.
“It’s not just a bad idea because it’s something that would never be safe to launch,” he said. “Even researching the topic is not only a waste of money, but actively dangerous.””.
Keith, a professor in the Department of Geophysical Sciences at the University of Chicago, argues that the risks involved in solar geoengineering are well known, are not as severe as critics claim and do not weigh against the potential benefits.
Keith said that if the technique could delay global warming by even one degree Celsius over the next century, it could help prevent millions of heat-related deaths each decade.
To understand how controversial Keith’s work may be, let’s recount what happened when he attempted to conduct an initial test in preparation for a solar geoengineering experiment known as Scopex.
Keith, then a professor at Harvard University, intended to disperse a few kilograms of mineral dust at an altitude of about 20 kilometers and observe how the dust behaved as it floated through the sky.
A test was planned for 2018, possibly over Arizona, but Keith was unable to secure a partner who could launch a high-altitude balloon. When some information about the plan became public, a group of indigenous people opposed it and issued a manifesto against geoengineering.
Three years later, Harvard contracted Swedish Space Corporation to launch a balloon that would carry the test equipment. But local groups again protested.
The Saami Council, which represents indigenous peoples, said it believes solar geoengineering “is the complete opposite of the respect with which we as indigenous peoples are taught to treat nature.”
Greta Thunberg, the Swedish environmental activist, joined the chorus. “Nature is doing everything it can,” she said. “It is screaming at us to back off, to stop… and we are doing the opposite.”
Within a few months, the experiment was discontinued.
Opponents of solar geoengineering cite several major risks. They say it could create a “moral hazard” by giving people the wrong impression that there is no need to rapidly reduce fossil fuel emissions.
The second major concern is about unintended consequences.
“This is a very dangerous path,” warned Beatrice Rindevall, president of the Swedish Society for Nature Conservation, an environmental organization that opposed the experiment. “It could cause a shock to the climate system.”, could disrupt hydrological cycles and could exacerbate extreme weather and climate instability.”
Moreover, once solar geoengineering begins to cool the planet, if those actions are abruptly stopped, a sudden increase in temperatures could occur due to a phenomenon known as a “termination shock.” The planet could experience “perhaps a massive increase in temperature, in a world completely unprepared for such circumstances, in just five to ten years, which would affect the Earth’s climate in a way that it probably hasn’t seen since the asteroid that wiped out the dinosaurs,” Pierrehumbert explained.
On top of all this, there are fears that some rogue actors will use solar geoengineering and that this technology could be weaponized. To make matters worse, there is the fact that sulphur dioxide can affect human health.
Keith insists that such fears are exaggerated. He argues that while there would indeed be additional air pollution, the risk is minimal compared to the benefits.
CONTENT FOR SUBSCRIBERS
In 2006, Keith and Gates were introduced by a mutual acquaintance, who wanted to learn more about some technologies that could help combat global warming.
“I don’t know if that will ever be used,” said Gates, who has invested heavily in climate technology. “But I do think the most logical thing to do is to do the research and understand it.””.
Later in 2009, Keith founded Carbon Engineering, a company that developed a process to suck carbon dioxide out of the atmosphere. Last year, Occidental Petroleum bought Carbon Engineering for $1.1 billion.
Occidental is now building carbon capture plants. It plans to sell carbon credits to large companies willing to offset their emissions. Critics say this will only delay the phase-out of fossil fuels, and will also generate profits for an oil company.
“Of course I don’t like that it was sold to an oil company.”said Keith, who added that he plans to donate most of the money he made from the sale of Carbon Engineering perhaps to a conservation group.
“I am now even more motivated to push solar geoengineering because the rational argument for it seems stronger,” he said. “While there are still a lot of very strong individual voices in opposition, many people in important positions in public policy are taking it seriously, and that is very exciting.”
#scientists #unusual #risky #plan #cool #Earth
