Geoengineering is an emerging branch of environmental science which seeks to alleviate environmental problems not by altering the patterns of human behaviour which led to the problems in the first place, but by using technology to make sweeping alterations to the natural environment in the hope of producing some desirable effect. Geoengineering would involve the deliberate modification of Earth’s environment on a large scale to suit human needs and promote habitability. Click image to enlarge.
Many scientists now support serious research into geoengineering.
Of the various geoengineering proposals, the ones that shade the earth from the sun could bring about the most immediate effects. But all of them have drawbacks and side effects that probably cannot be anticipated.
Pumping sulfur dioxide into the stratosphere, as volcanoes do, is the most well established way to block the sun. Other proposals call for brightening clouds over the oceans by lofting sea salt into the atmosphere and building a sunscreen in space. Read more here or here.