Climate Change, Climate Models and Geoengineering the Earth

Changes in the Earth’s orbit around the Sun, volcanic eruptions and variations in emission of solar radiation are the primary natural causes climate change on all but the longest time scales. Since the start of the Industrial Revolution, human activity has increased atmospheric concentrations of carbon dioxide, methane and nitrous oxide. These greenhouse gases are efficient absorbers of terrestrial radiation and are primarily responsible for the observed increase in temperature during the past 150 years. Mitigation efforts to reduce the release of greenhouse gases have been unsuccessful so far. Geoengineering proposals to counteract the enhanced greenhouse effect include ideas to reduce the solar radiation absorbed at the surface and to increase the amount of terrestrial radiation that is lost to space. These proposals face questions about their effectiveness, cost and feasibility. Climate models, which have already been used to examine the impact of anthropogenic climate change, provide a way to test the effectiveness of the geoengineering proposals. Those models also are a means to determine if the proposals might result in other undesirable climate changes. This chapter examines the potential effectiveness and feasibility of some of the most well known geoengineering proposals.