Aside from those who identify as climate change deniers, most of humankind is generally concerned about global warming. Some scientists think that ongoing and planned efforts to reduce carbon dioxide emissions aren't enough and are promoting a controversial idea called geoengineering. It's basically manipulating Earth's natural systems to offset the warming effect.
But not everyone is on board. As far back as 2010, experts have cautioned lawmakers on their efforts until scientists better understand its effects. Geoengineering could have unintended or unforeseen consequences, and experts currently have no way to address, for instance, the plans of one country affecting the climate of another.
Dr. Raymond Pierrehumbert, professor of physics at University of Oxford, is one of the leading scientists opposing geoengineering. In a 2015 article for Slate he said "the idea of 'fixing' the climate by hacking the Earth's reflection of sunlight is wildly, utterly, howlingly barking mad."
Most scientists in favor of drastic measures agree there's no way to know how the planet will react to geoengineering. "As far as research goes, everybody agrees that we need a much better understanding of certain aspects of the climate system (especially cloud responses) before one could even begin to assess what [solar radiation management] would do to the planet," Pierrehumbert says. "We need to be able to monitor the Earth's radiation budget much more accurately as well."
Pierrehumbert also says one of the biggest problems with geoengineering is what he calls millennial commitment, which means once we start taking drastic geoengineering actions, we cannot stop. The effects of climate change will continue building, and if the solar engineering efforts cease, the pent-up global warming could happen all at once, instead of gradually.
"That is an unacceptable burden to place on future generations and would make living with the nuclear Armageddon peril of the Cold War look like a cake-walk," Pierrehumbert says.
So what exactly are types of geoengineering that scientists are considering to avert a climate disaster? We'll take a look at five of them, from the least to most radical.