From The Article:
Solar geoengineering

There’s a dramatic option for stopping, or even reversing, rising global temperatures, but it comes with significant possible risk.

Solar geoengineering would reflect light and heat away from Earth and back into space by injecting aerosols into the stratosphere, the second layer of Earth’s atmosphere. For now, it only exists in computer models, but the first experiment is being planned by Harvard researchers.

Solar geoengineering is one of two emerging technologies that could manipulate the atmosphere and reduce climate risk. The other is directly removing carbon dioxide from the atmosphere, which doesn’t currently exist on a big enough scale.

If solar geoengineering were deployed, it would affect the entire atmosphere and be humanity’s largest-ever global endeavor. While it is the only known technique that could stop rising temperatures, there’s still a lot we don’t know, including whether it could destabilize local and global climate or ecosystems. Manipulation on this scale without understanding the effects could turn out to be catastrophic for the human race. The technology could also be cheap enough (as low as $10 billion a year) that it could be wielded by one country or a wealthy individual, introducing the possibility of reckless use.