Solar geoengineering: why leading scientists oppose Bill Gates’ idea to curb global warming

But not everything in this movie is science fiction. The possible strategy against global warming that the film talks about actually exists: it is the principle of solar geo-engineering.

A research center at the prestigious Harvard University in the United States is dedicated to studying this concept.

Billionaire Bill Gates is one of its biggest followers, and has donated millions to research.

It is also real that we have the monumental task of limiting global temperature rise to 1.5°C and that climate disasters will become routine around the world in the near future.

Last Monday, April 4, the United Nations climate change body released a new report that sets an ultimatum: it’s now or never if we are to avoid severe droughts, extreme heat, devastating floods and mass extinctions of species.

If the targets set are not met and the changes have only modest results, the average temperature of the planet will increase by 2.1°C to 3.5°C.

Some experts fear that solar geoengineering is gaining traction as a solution in this time of desperation, even though it is likely to generate irreversible environmental and political side effects: the technique could be used as a weapon of unpredictable war, they warn.

But others argue that we can’t give up on finding solutions to the climate change emergency, a line of reasoning embraced by Bill Gates.

In January this year, more than 60 scientists from several countries launched an initiative to outright ban the development of this technique, which has only been studied in computer simulations and requires field trials.

This proposal warns that in addition to potentially disastrous results, solar geoengineering would not completely solve the problem of global warming, a point conceded by proponents of the concept.

And it could distract from a more important obligation that has been ignored: that of drastically reducing emissions of carbon dioxide (CO2), which traps heat in the atmosphere.

BBC News Brazil spoke to five Brazilian and American scientists, some critics and some supporters, to explain the implications of solar geoengineering.

There are various techniques that fall under the category of solar geoengineering, some of which involve ocean waters rather than the atmosphere.

However, the principle of the most debated technique today is inspired by large volcanic eruptions and is called the injection of stratospheric aerosols.

In 1991, Mount Pinatubo in the Philippines caused the second largest volcanic eruption of the 20th century, leaving more than 800 people dead and 10,000 homeless, and leaving a trail of destruction.

A natural phenomenon was also observed: the lava and ash ejected by the Pinatubo caused tons of sulfur dioxide in the stratosphere to act as a kind of mirror for the sun’s rays.

“When there is a lot of soot and solid particles in the upper atmosphere, solar radiation encounters these aerosols when it enters the atmosphere and is returned to space,” explains Tércio Ambrizzi, professor at the Institute. of Astronomy, Geophysics and Atmospheric Sciences from the University of São Paulo (USP).

“Solar radiation cannot pass through and reach the Earth’s surface, which prevents it from generating a high temperature,” he adds.

The scientists noted that the effects of the 1991 Pinatubo volcanic activity led to a 0.5°C drop in global temperature over the following years, a rate considered significant.

“The idea of ​​solar geoengineering is to inject aerosols into the stratosphere to inhibit that influx of solar energy. And with that, you will cause cooling,” Ambrizzi says.

“We know that the reason for the dinosaurs’ disappearance was the fall of a meteorite. One theory is that the impact caused a series of volcanic explosions all over the planet, generating a layer of aerosols which blocked the solar energy and lowers the global temperature.

To try to reproduce the phenomenon, the idea is to build special planes to reach the stratosphere (at an altitude of about 20-30 km) and dump chemical compounds there, such as sulphates and their variations.

This objective is considered quite achievable from a technological point of view.

Another factor in favor of solar geoengineering is its cost: $10 billion per year is the highest estimate, which is low compared to future losses due to global warming, already estimated at several trillions. .

But Stephen M. Gardiner of Washington State University, who studies ethical issues related to environmental problems and their impact on future generations, says there is a consensus “among responsible scientists” that the concept remains highly speculative.

“Even if we did decide to push research in this area, it would be a race against time to develop something that would only be implemented decades from now and would inevitably come with great risk.

For Gardiner, the growing attention to solar geoengineering is a product of the desperation gripping those aware of the climate catastrophe looming on the horizon.

“It’s spiraling out of control. It’s hard to deal with the persistent failures of conventional approaches, such as the Kyoto and Paris (climate) agreements.”

“So people are starting to latch on to anything. Even highly speculative, inherently risky and potentially geopolitically destabilizing events like this.”

According to the University of Washington professor, solar geoengineering would involve a deep concentration of political power and would require new global institutions that are more powerful and more ethical than those we have today.

“Without it, who would wield the power of geoengineering? It seems inevitable that it would thus become a superpower, which would create conflicts with other great powers,” Gardiner says.

Mr Ambrizzi of USP says that “you have no control over where aerosols are injected into the atmosphere. As there are wind flows in the upper atmosphere, there is intense circulation in the stratosphere”.

“Without this control, you can destabilize regions that are in equilibrium.

“Suppose Brazil decides to do this experiment, but Argentina doesn’t. Average temperatures start to drop here, but either increase in Argentina or drop much more than today.

“The Argentine government did not agree to this. Imagine, for example, that the country loses all its wine production and decides to sue Brazil.”

It also highlights the high degree of uncertainty in current weather and climate prediction models, which adds to the unpredictability of solar geoengineering at its current stage.

David Keith, a professor of applied physics and public policy at Harvard’s Kennedy School, is one of the main names cited when discussing the topic.

“In my view, there is strong evidence that solar geoengineering could significantly reduce some climate risks in the second half of this century,” says Keith.

“Climate models consistently show that a combination of emission reductions and uniform and consistent solar geoengineering would reduce average and maximum temperatures more than emission reductions alone.”

“Given that an additional 1°C increase is proven to be most damaging to the hottest regions of the planet, and given that the poorest and most vulnerable are concentrated in these hot regions, it seems likely that solar geoengineering would be particularly effective in reducing risk in these locations.”

Holly Jean Buck – author of “After Geoengineering: Climate Tragedy, Repair and Restoration” – advocates this technique because of the risks posed by climate change.

She agrees that it is necessary to understand what the impacts of solar geoengineering would be on the planet and that many studies are needed before it can be implemented.

“However, the petition [contre le développement de la technique] calls for measures that would affect the ability to fund, conduct and evaluate research in a transparent way.

Both recognize that solar geoengineering risks distracting attention from the main objective, namely the reduction of carbon emissions, and that this technique could only work as a complement to this objective.

Emilia Wanda Rutkowski – professor at the Faculty of Civil Engineering, Architecture and Urban Planning at the State University of Campinas (Unicamp) – is one of the signatories of the document calling for a moratorium on the development of geo -solar engineering.

“Trying to find a solution without changing the essence of the problem [du réchauffement climatique] is not a real solution,” Rutkowski said.

She claims that the problem “prolongs”.

“Why not start with what you know is the root cause?” she asks.