Arctic Sea-Ice

Perched on sea-ice off Canada’s northern coast, parka-clad scientists watch saltwater pump out over the frozen ocean. Their goal? To slow global warming. As sea-ice vanishes, the dark ocean surface can absorb more of the Sun’s energy, which accelerates warming. So the researchers want to thicken it to stop it melting away. Welcome to the wackier side of geoengineering – deliberately intervening in the Earth’s climate system to try to counteract the damage we have done to it. Geoengineering includes more established efforts to lock up planet-warming gases, such as planting more trees and burying carbon underground. But more experimental measures aim to go a step further, seeking to reduce the energy absorbed by the Earth. Many scientists are strongly opposed, warning that such attempts distract from the critical step of cutting carbon emissions and risk doing more harm than good. But a small number of advocates claim the...