Geoengineering is an instance of planetary engineering. Geoengineering is the deliberate modification of Earth's environment on a large scale "to suit human needs and promote habitability".

Typically, the term is used to describe attempts to counter the effects of human-induced climate change. However, others define it more narrowly as focusing only on the mineralogy and hydrology of the Earth. The term geoengineering is distinct from environmental damage and accidental anthropogenic climate change, which are side-effects of human activity, rather than an intended consequence. Definitions of the term are not universally accepted.

Global warming has become such an overriding emergency that some climate experts are willing to consider schemes for partly shielding the planet from the sun's rays. But no such scheme is a magic bullet.