In the not-too-distant future, Earth faces the tragic consequences of an experiment designed to stop climate change: dumping chemicals into the sky to form a barrier against the sun’s rays that heat the planet. The attempt fails. The world then enters a post-apocalyptic reality.
This is the plot of “Expresso do Amanhã”, a 2013 production directed by South Korean Bong Joon-Ho, the renowned filmmaker of “Parasite”..
Not all of the above is science fiction. The idea put forward in the film as a possible strategy against global warming actually exists: it is the principle of solar geoengineering.
There is a research center at the prestigious Harvard University in the USA dedicated to studying the concept. Billionaire Bill Gates is one of its great enthusiasts, donating millions to research.
And so is the monumental task of limiting the rise in global temperature to 1.5°C and the threat on the horizon of climate catastrophes as routine in the world.
On Monday, the United Nations’ climate change arm released a new report, which carries an ultimatum: It’s now or never to change a perspective on severe droughts, extreme heat, devastating floods and mass extinction. of species.
If the goals set are not achieved and the changes have only modest results, the average temperature in the world will rise in a range between 2.1 °C and 3.5 °C.
Some experts warn that solar geoengineering can gain strength as a solution in this desperate moment, even with the possibility of generating irreversible side effects on the environmental side and dangerous in politics – the technique could be used as an unpredictable weapon of war.
Others say that one cannot give up researching solutions in the face of the urgency of climate change – a line of reasoning adopted by Bill Gates when talking about geoengineering.
In January of this year, more than 60 scientists from several countries launched an initiative to simply ban the development of the technique, which has only been studied in computer simulations and requires field tests.
The undersigned says that, in addition to potentially disastrous results, solar geoengineering does not completely solve the problem of global warming – a point admitted by supporters of the concept.
And it could divert attention from the most important obligation that has been ignored: that of significantly reducing emissions of carbon dioxide (CO2) that trap heat in the atmosphere.
BBC News Brasil spoke with five scientists from Brazil and the US, including critics and advocates, to explain the implications of solar geoengineering.
How does solar geoengineering work?
There are different techniques that are classified as solar geoengineering, including some that intervene in ocean waters rather than the atmosphere.
The principle of the most debated technique today, however, is inspired by large volcanic eruptions and is called aerosol injection into the stratosphere.
In 1991, Mount Pinatubo, in the Philippines, promoted the second largest eruption of a volcano in the 20th century. It left more than 800 dead and 10,000 homeless, in addition to a trail of destruction.
A natural phenomenon was also observed: the lava and ash expelled by Pinatubo caused tons of sulfur dioxide in the stratosphere to act as a kind of mirror for the sun’s rays.
“When you have lots and lots of soot and solid particles up there in the upper atmosphere, solar radiation encounters these aerosols as it enters the atmosphere and it’s reflected back into space. Solar radiation can’t get through and reach the Earth’s surface. , which would have a high temperature”, says Tércio Ambrizzi, professor at the Institute of Astronomy, Geophysics and Atmospheric Sciences at the University of São Paulo (USP).
Scientists noted that the effects of Pinatubo’s volcanic activity in 1991 led to a 0.5°C drop in global temperature in the following years — a rate considered significant.
“The idea of ​​solar geoengineering is to inject aerosols into the stratosphere in order to inhibit this influx of solar energy. And with that you would be inducing a cooling”, says Ambrizzi.
“We know that the reason for the disappearance of the dinosaurs was the fall of a meteorite. Along with this, there is the theory that the impact caused a series of volcanic explosions across the planet, generating an aerosol layer that prevented the entry of solar radiation and lowered the global temperature.”
To try to reproduce the phenomenon, the idea is to build special aircraft to reach the stratosphere (in a range around 20 to 30 kilometers in altitude) and dump chemical compounds, such as sulfates and variations.
This objective is considered quite feasible from a technological point of view.
Another factor in solar geoengineering sold as an advantage is the cost of the undertaking: US$ 10 billion annually at the highest estimates — a low figure compared to future losses from global warming, calculated already in the trillions.
But Stephen Gardiner of Washington State University, who studies ethical issues in environmental problems and the impact on future generations, says there is consensus “among responsible scientists” that the concept is still highly speculative.
“Even if we decided to strongly push research in this field, it would be a race against the clock to develop something that would only be put into practice decades from now and inevitably at great risk.”
For Gardiner, the growing attention to solar geoengineering is a product of the desperation that is gripping those who are aware of the climate catastrophe on the horizon.
“It’s getting out of hand. It’s hard to deal with the persistent failures of conventional approaches like the Kyoto and Paris (climate) accords. So people are starting to cling to anything. Even highly speculative, inherently risky and potentially geopolitically destabilizing events like this are starting to get attention.”
The University of Washington professor says that solar geoengineering would involve a deep concentration of political power and would need new global institutions more powerful and more ethical than the ones we have today.
“Without that, who would wield the power of geoengineering? It seems inevitable that in this way it would be a superpower, which would create conflicts with other great powers,” says Gardiner.
Ambrizzi, from USP, says that “you have no control over where the aerosols injected into the atmosphere go. Because in the upper atmosphere there are wind flows, there is an intense circulation in the stratosphere. Without this control, you can destabilize regions that are balanced.” .
“Suppose that Brazil decides to do this experiment, but Argentina does not. Average temperatures start to drop here, but they increase in Argentine territory or decrease much more than the current ones. The Argentine government has not given consent for this. Imagine, for example, that the country loses all its wine production and decides to sue Brazil.”
He also points out the high degree of uncertainty existing in current weather and climate forecast models, reinforcing the unpredictability of solar geoengineering at its current stage.
In defense of research
David Keith, professor of applied physics and public policy at the Harvard Kennedy School, is one of the top names cited when talking about the topic.
“My reading is that 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 cutting emissions and uniform, consistent solar geoengineering would reduce average and maximum temperatures more than cutting emissions alone.”
“Given the evidence that a further 1°C rise in heat harms the hottest regions of the planet the most, and given that the poorest and most vulnerable are concentrated in warm regions, it seems likely that solar geoengineering would be particularly effective in reducing risks in these places”, he adds.
Holly Jean Buck, author of the book “After Geoengineering – Climate Tragedy, Repair and Restoration”, defends the research because of the risks being posed by climate change.
She agrees that it is necessary to understand what would be the impacts of solar geoengineering on the planet and that many studies are needed before putting the technique into practice.
“However, the undersigned [contra o desenvolvimento da técnica] calls for measures that would impact the ability of research to be transparently funded, conducted and evaluated.”
Both recognize that there is a risk that solar geoengineering will distract from the main focus, cutting carbon emissions, and that the technique only works as a complement to that goal.
‘Palliative’
Emilia Wanda Rutkowski, professor at Unicamp’s Faculty of Civil Engineering, Architecture and Urbanism, was one of the signatories of the document that calls for a moratorium on the development of solar geoengineering.
“Trying to find a solution without changing the essence of the problem [do aquecimento global] It’s not really a solution. It’s a palliative. And every palliative tends to show a problem further down the road that you didn’t notice at the time of the emergency,” says Rutkowski.
She says she’s been “pushing with her belly” the issue. “Then why don’t you start with what you know is the essential cause?”
