In the not-too-distant future, Earth is facing the tragic consequences of an experiment designed to halt climate change: pouring chemicals into the sky to create a barrier against the sun’s planet-warming rays.

The attempt fails and the world enters a post-apocalyptic reality.

This is the subject of the 2013 movie “The Express of Fear” directed by the famous director of the movie, South Korean Bong Joon-Ho. interference.

But not everything the movie raises is science fiction. The possible strategy against global warming that the movie talks about actually exists: solar geoengineering.

The prestigious Harvard University in the United States has a research center dedicated to studying this concept.

billionaire Bill Gates is one of his big buffs, and donated millions to his research.

It is also a fact that we have a huge task to limit the global temperature increase to 1.5°C and that in the near future climate disasters will become routine in the world.

Last Monday, April 4, the United Nations Organization’s (UN) arm dedicated to climate change released a new report that brings an ultimatum: Now or never if we want to avoid severe droughts, extreme heat, devastating floods and mass masses. extinction of species.

If the set goals are not met and the changes yield modest results, the average temperature around the world will rise by a range. Between 2.1°C and 3.5°C.

Some experts fear that solar geoengineering will gain traction as a solution in this time of desperation, although it is a possibility. cause irreversible side effects Environmentally and politically dangerous: the technique could be used as a weapon of unpredictable warfare, they warn.

Others, however, affirm that seeking solutions in the face of the urgency of climate change, a line of reasoning adopted by Bill Gates.

In January of this year, more than 60 scientists from various countries launched a direct initiative prohibit the development of technology, has only been studied in computer simulations and requires field testing.

This proposal, in addition to the potentially disastrous consequences, is an important part of solar geoengineering. not fully resolved The problem of global warming is a point accepted by supporters of the concept.

Y can divert attention the most important overlooked obligation: to significantly reduce emissions of carbon dioxide (CO2), which traps heat in the atmosphere.

BBC News Brazil spoke with five scientists, some critics and some supporters from Brazil and the US to explain the results of solar geoengineering.

How does it work?

There are different techniques that are classified as solar geoengineering, some of which work on ocean waters rather than the atmosphere.

However, the principle of the most discussed technique today inspired by major volcanic eruptions and it is called aerosol injection into the stratosphere.

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

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

“When there is so much soot and solid particles in the upper atmosphere, when solar radiation enters the atmosphere it meets these aerosols and is reflected back into space,” explains Tércio Ambrizzi, professor at the Institute of Astronomy, Geophysics and Atmospheric Sciences. University of Sao Paulo (USP).

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

Scientists believe that the effects of Pinatubo volcanic activity in 1991 0.5°C drop in global temperature in subsequent years, a rate considered significant.

“The idea of ​​solar geoengineering is to inject aerosols into the stratosphere to block the flow of solar energy. And with that you’d be to cause coldAmbrizzi says.

“We know that the reason the dinosaurs disappeared was a meteorite fall. There is a theory that the impact caused a series of volcanic eruptions around the planet. creating an aerosol layer preventing the penetration of solar energy and global temperature dropped.

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

This goal is evaluated quite doable from a technological point of view.

Another factor in favor of solar geoengineering is its cost: $10 billion a year is the highest estimate, low compared to the estimated losses from global warming in the trillions already.

But there is consensus “among responsible scientists” that the concept remains highly speculative, says Stephen M. Gardiner of Washington State University, who has studied the ethical issues associated with environmental issues and their impact on future generations.

“Even if we decide to push research in this area very hard, it would be a race against time to develop something that will only be implemented decades from now and will inevitably include the following. It’s a big risk.”

According to Gardiner, the growing interest in solar geoengineering is a product of the desperation that has caught 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 traditional approaches like the Kyoto and Paris (climate) agreements.”

“So people are starting to hold on to everything, even to events. highly speculative, inherently risky and potentially such geopolitically destabilizing«.

The University of Washington professor says solar geoengineering will involve a deep concentration of political power and will require new global institutions that are stronger and more ethical than we have today.

“Without this, who will harness the power of geoengineering? In this way, it seems inevitable that there will be a superpower that will create conflicts with other great powers,” says Gardiner.

Ambrizzi of the USP states, “There is no control over where the aerosols injected into the atmosphere go. Because there are wind currents in the upper atmosphere, there is intense circulation in the stratosphere”.

“Without that check, Stabilized regions can be destabilized».

“Let’s say Brazil decides to do this experiment, but Argentina doesn’t. Average temperatures start to drop here, but rise in the Argentine region or drop much more than current ones.

“The Argentine government did not approve of this. For example, imagine that the country lost all of its wine production and decided to sue Brazil.”

also points out high degree of uncertainty present in current weather and climate forecasting models, reinforcing the unpredictability of solar geoengineering at its current stage.

in defense

David Keith, professor of applied physics and public policy at the Harvard Kennedy School, is one of the main names mentioned in the discussion.

“My reading is that there is strong evidence for solar geoengineering. can significantly reduce some climate risks In the second half of this century,” says Keith.

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

“Given the evidence that an additional 1°C increase will do the most damage to the hottest regions of the planet, and the poorest and most vulnerable are concentrated in these hot regions, it seems likely. solar geoengineering will be particularly effective in reducing risks. in these places,” he adds.

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

He acknowledges that it is necessary to understand what the effects of solar geoengineering will be on the planet, and that a lot of work is needed before it can be put into practice.

“But the request [contra el desarrollo de la técnica] requires precautions will affect the ability to fund, conduct and evaluate research. transparent.”

Both acknowledge that there is a risk that solar geoengineering will move away from the main focus, reducing carbon emissions, and that the technique only works in addition to that goal.

“palliative”

Emilia Wanda Rutkowski, professor in the Campinas State University (Unicamp) School of Civil Engineering, Architecture and Urbanism, was one of the signatories of the document calling for a moratorium on the development of solar geoengineering.

Trying to find a solution without changing the essence of the problem [del calentamiento global] this is not a real solution,” says Rutkowski.

He claims that the question is “prolonged”.

“Why don’t you start with what you know? real reason?“She’s wondering.