The term geoengineering refers to the large scale manipulation of the environment to bring about specific environmental change

Sulphates in the stratosphere

When volcanoes erupt they release sulphates which are known to have a cooling effect on global temperatures by reflecting solar energy back into space. Some scientists are proposing to increase levels of sulphates to simulate this effect. However, the sulphates will have unknown impact on ecosystems, including acid rain and localised climatic impacts potentially causing droughts. Nobel prize winner Paul Crutzen, who advocated research into sulphate aerosols as a last ditch solution to global warming, predicted around half a million deaths as a result of particulate pollution.