The planet is getting warmer. Scientists say governments aren’t doing enough to reduce fossil fuel emissions to keep temperatures from rising more than 1.5 degrees Celsius in coming decades. As that reality sinks in, experts are starting to consider geoengineering, which The Daily Beast‘s science writer Tony Ho Tran calls “one of the most controversial and consequential climate change-fighting tactics yet.” Here’s everything you need to know about geoengineering: 

What is geoengineering?

The term refers to using man-made technologies “to artificially modify the Earth’s climate,” explains The Daily Beast‘s Ho Tran. The concept might sound “futuristic,” writes Robert Litan for Foreign Affairs, but it was first floated in 1965 when scientific advisers to then-President Lyndon Johnson “suggested that some kind of tinkering with the planet’s mechanics might be necessary” to offset the “deleterious” climactic changes that could be caused by carbon emissions. 

In the years since, researchers have developed a range of geoengineering projects to try to reverse or limit the damage humans have done to the Earth’s climate. For example, direct air capture aims to suck carbon dioxide out of the atmosphere using technology. Iron fertilization seeks to seed the ocean to stimulate the growth of carbon-absorbing phytoplankton. Other projects would influence the weather directly.

Why are we talking about it now?

Geoengineering is being taken more seriously “as the pace and destructiveness of extreme weather events seem to be quickening beyond even some of the most pessimistic forecasts,” says Litan. For example, the White House announced it is investigating a technique that “essentially involves spraying fine aerosols into the atmosphere to reflect sunlight away from the Earth,” explains Ho Tran. That might sound “a bit bonkers,” he writes, but the world has seen “inadvertent solar radiation management” before: When the Tambora volcano in Indonesia erupted in 1816, temperatures dropped by as much as 3 degrees Celsius in Europe and North America that summer due to the huge amounts of sunlight-blocking debris the volcano spewed into the atmosphere.

At the COP27 climate conference in Egypt, UNESCO organized a panel to discuss “scientific, social, and cultural perspectives” on geoengineering, saying the idea is gaining more traction but “raises a host of ethical concerns and questions.”

What kinds of concerns?

There are geopolitical implications to consider. Interventions associated with geoengineering “can cross borders, and what may be good for one country may not be good for its neighbors,” Tracy Raczek, former climate adviser to the UN secretary general, writes in an article for London-based think-tank Chatham House. She points to Iran, which has accused Israel of stealing its water through cloud-seeding. India and other nearby nations are growing increasingly concerned about China tinkering with the weather over some of its cities.

But on a more fundamental level, many forms of geoengineering — and their potential side effects — need more researching before they’re seriously considered. As Bill McKibben explains at The New Yorker, blocking the sunlight could alter plant photosynthesis, damage the ozone layer, and even change the color of the sky from blue to “milky.” And once you start pumping aerosols into the atmosphere to cool the planet, you can’t stop unless the heat-trapping emissions are gone. Otherwise, temperatures will rapidly rise. 

But could geoengineering work?

Geoengineering would probably cool the planet, and quickly. According to an article in the Harvard Environmental Law Review, it could also “reduce the rate of sea-level rise, sea-ice loss, heatwaves, extreme weather, and climate change-associated anomalies in the water cycle.” Geoengineering methods may “sound insane,” says science journalist and astrophysicist Graham Phillips in The Sydney Morning Herald. “But the voice to explore them has been steadily growing louder, and serious scientific research is starting to be done on this terrestrial tinkering – because not tinkering may be even more insane.”

Even so, large-scale geoengineering is probably not going to happen any time soon. Former BP chief John Browne, now chair of climate growth equity venture BeyondNetZero, estimates “it will take at least a decade to establish the scientific and bureaucratic institutions needed to govern this activity.” He adds geoengineering is “not desirable, is fraught with risk, and does not need to be done immediately.”