Many geoengineering schemes have been proposed, but all can be reduced to two main strategies: reduce the amount of greenhouse gases in the atmosphere (increase the amount of infrared radiation escaping to space) or reduce the amount of solar energy the Earth system absorbs. Two of the most common examples of these geoengineering china travelstrategies involve removing carbon from the atmosphere by adding fertilizer to selected regions of the ocean to increase phytoplankton growth and reflecting more sunlight by injecting tiny, non-absorbing particles (aerosols) into the upper atmosphere (stratosphere).

While both of these geoengineering examples might counter global warming for a time, they could also have significant drawbacks. Increased fertilizers and/or phytoplankton growth could havechina tours unintended consequences on ocean ecosystems, including increased ocean dead zones and toxic blooms. Adding aerosols to the upper atmosphere could modify the chemistry of the upper atmosphere, affecting ozone and thereby having possible unintended impacts on the lower atmosphere.