Climate engineering (or geoengineering) refers to the deliberate manipulation of the atmosphere to alter the climate in ways that are desirable. A well-known example is cloud seeding, or the addition of particles to the atmosphere in an effort to encourage precipitation.

However, cloud seeding is climate engineering on a small scale. Other atmospheric alterations tend to be on a much larger, and even global scale. How it began, is that in 1945, a gathering of scientists at Princeton University in New Jersey agreed that manipulating climate was possible. Their motivation was a desire to control the weather as a means of decreasing crop production, particularly in the Soviet Union.

This was seen as a way of dealing with the perceived military threat posed by the Soviet Union to the United States. Indeed, during the Cold War (1945–1991) that took place between the two nations, the United States conducted research on what was called climatological warfare. This research was actually tested in the field, when cloud seeding was tried unsuccessfully in the early 1970s during the Vietnam war (1954–1975) to bog down Vietcong troop movements.

In cloud seeding, particles of silver iodide (AgI) are scattered into clouds from an aeroplane. The particles act as surfaces, on which water vapour precipitates to form raindrops. If the drops are heavy enough, they will fall as rain or snow.

By the 1970s, the global warming hoax was picking up speed and the notion that human activities were the cause was also gaining some support. Schemes to spread reflective material on the ocean surface or seeding the atmosphere to promote the formation of sunlight-reflecting clouds had then been proposed.

Other climate engineering schemes were intended to trap CO2 so that the gas would not accumulate in the atmosphere. It was said that the massive planting of trees would produce forests capable of soaking up carbon. Adding nutrients to the ocean could apparently  fuel the growth of carbon-absorbing plankton, which would transport the carbon to the ocean floor when they died.

An equally exotic plan was to trap CO2 being emitted from the furnaces of coal burning facilities, compress the gas to turn the CO2 into a liquid, and pump the liquid deep in the earth or to the bottom of the ocean (an undersea experiment was actually done in 1999, and research on the technique began in 2007 in countries including Japan and the United States).