Last year, a US business called Make Sunsets launched two weather balloons above Mexico’s Baja California peninsula, sparking a heated discussion about one of the most divisive climate change solutions.

It was intended for the helium- and sulfur dioxide-filled balloons to soar far into the stratosphere. There, they would explode, scattering their cargo of sulfur dioxide particles that reflect sunlight and briefly cooling the Earth.

Some people wrote it off as a stunt. If any particles were actually released, or even if the balloons reached the stratosphere, is unknown. But the Make Sunsets effort is crucial because it represents a turning point for solar geoengineering, a contentious climate solution.

For those who embrace it, solar geoengineering is a necessary solution as the globe races toward a climatic catastrophe. According to detractors, the technology is so risky that we shouldn’t even look at it.

Solar geoengineering: What is it?

Solar geoengineering, commonly referred to as solar radiation management, is essentially an effort to lower the planet’s temperature by deflecting sunlight or increasing heat evaporation into space.

There are three primary methods:

Marine cloud brightening includes sprinkling sea salt over low clouds over the ocean to make them more reflective.

To thin them so they don’t trap as much heat, wispy clouds higher up in the atmosphere are the goal of cirrus cloud thinning, which seeds them with aerosol particles.

But stratospheric aerosol injection is the approach that has received the most study. To reflect sunlight into space, aerosols, such as sulfur dioxide particles, are sprayed into the stratosphere, more than 12 miles above the surface of the Earth. It might be accomplished using balloons or customized aircraft with high-altitude capabilities.

The concept is inspired by volcanoes. Sulfur dioxide released high into the atmosphere by Mount Pinatubo’s eruption in the Philippines in 1991 had the effect of briefly cooling the earth by 0.5 degrees Celsius (nearly 1 degree Fahrenheit).

Why has solar geoengineering gained so much attention?

Though the concept has been present since the 1960s, it is currently receiving increasing attention due to how slowly climate change mitigation efforts are progressing.

Critical warming thresholds are being reached, and once they are, there is a significantly increased risk of major flooding, drought, wildfires, and food shortages.

To reduce the quantity of sunlight reaching the planet, scientists have even gone so far as to suggest spraying moondust in its direction.

“I wish geoengineering didn’t exist!” Make Sunsets’ founder, Luke Iseman, told the associated press via email. However, he claimed that “there are no other practical solutions to stay below 2 [degrees Celsius].”

While virtually no one asserts that solar geoengineering can eliminate climate change-causing pollutants and reverse global warming, proponents contend it might have a significant planetary cooling effect for a relatively low cost. According to a Harvard study published in 2018, it would cost about $2.25 billion over 15 years.

Without a doubt, the world has to reduce emissions, according to Harvard University’s David Keith, a professor of applied physics and public policy. However, he continued, that does not imply that we should disregard other climate solutions.

I’m not saying we have to use solar geoengineering, but I think it’s worthwhile taking into account all the options, he added.

There are valid reasons to be wary of solar geoengineering, according to Chris Field, director of the Stanford Woods Institute for the Environment, who spoke to the associated press. However, he added, “we have a responsibility to study the opportunities, as well as the hazards” if it “may provide a path for lessening the impacts of climate change on millions of the world’s most vulnerable people (and on ecosystems).”

Climate change has already put some of the most vulnerable nations, such as low-lying island countries, in danger of extinction. More than 700 climate scientists participated in a 2019 study, and the results showed that those who anticipated catastrophic climate damage in their home nations were more in favor of solar geoengineering.

Why is it so divisive?

The technology, in the opinion of its detractors, might pave the way for an almost limitless number of potentially disastrous outcomes.

Because the hazards are so great, solar geoengineering isn’t suddenly a good solution just because we’re desperate, according to Lili Fuhr of the Center for International Environmental Law, who spoke to the associated press.

Some worries changing the planet’s thermostat could change the monsoons and rainfall patterns, potentially having disastrous effects on crops.

The likelihood of violence could rise as a result of different effects in different places, with some areas benefiting and others suffering.

According to Chukwumerije Okereke, a professor of global climate and environmental governance at Alex Ekwueme Federal University in Nigeria, “when things go wrong, the impoverished people are usually the ones who suffer the most.”

According to Okereke, suggestions have already been made for African nations to serve as testing grounds for the technology. “It is a diversion from the kinds of policies and assistance that ought to go to Africa.”

The ozone layer, which protects the planet from damaging ultraviolet rays and is now on course to heal itself thanks to the effectiveness of a ban on ozone-depleting chemicals, might also be harmed by solar geoengineering.

The challenges of implementation are another.

Solar geoengineering would need to be regularly maintained because aerosol particles rarely linger in the atmosphere for longer than a year. According to Raymond Pierrehumbert, a physics professor at Oxford University, if global warming stops, there is a risk of “termination shock,” which would release all the warming that has been stored up and is “waiting in the wings, ready to slap the Earth in the face.”

Frank Biermann, professor of global sustainability governance at Utrecht University in the Netherlands, told the associated press that it would also call for unheard-of levels of international cooperation. He said that this would need all nations, even those engaged in active conflict, to work together indefinitely.

One of the main arguments against solar geoengineering is that polluters might use it as a tool to keep polluting, and governments might use it as a diversion from measures to cut pollution that warms the globe.

A call for an “international non-use agreement” to limit the advancement of solar geoengineering was made in 2021 by a group of close to 400 experts.

According to Biermann, governments should take into account solar geoengineering in the same manner they do chemical, biological, and nuclear weapons, as well as arctic mining.

What has been the current status?

Particularly in the US, there has been a surge of interest in technology.

The National Oceanic and Atmospheric Administration received $4 million from Congress in 2019 for stratospheric research, some of which was for solar geoengineering. Additionally, the Biden administration unveiled a five-year research plan to investigate the idea last year.

The US should commit up to $200 million to a research program to better comprehend solar geoengineering, including its viability, effects on society and the environment, and public views, according to a 2021 study from the National Academy of Sciences.

Funding for research is also provided by organizations. The UK-based Degrees Initiative announced in February that it will be investing $900,000 in a study to examine how technology can impact the Global South in nations in Africa, Asia, and South America.

Outdoor studies have so far encountered significant resistance and have had a difficult time getting started.

After receiving objections from the local Indigenous Sami population, Harvard University researchers’ attempt to test a high-altitude balloon in Arctic Sweden in 2021 was abandoned. Solar geoengineering “entails chances of catastrophic repercussions,” according to a letter written on behalf of the Sami Council.

Additionally, the Mexican government declared in January that solar geoengineering experiments would be prohibited after Make Sunset’s balloon launch.

Arguments between those who believe there is a duty to explore solar geoengineering as a potential last-chance solution and those who are certain it is the way to catastrophe are only likely to intensify as the planet warms and solar geoengineering transitions from science fiction to mainstream.

But opponents like Biermann are steadfast in their resistance.

It’s incredibly dangerous. It can’t be ruled over. It’s wrong,” he declared. And it represents one of the largest threats to the status quo of climate policies.