Climatic impact of alternative energy sources

Detailed evaluations have suggested that the order of magnitude of energy demand 50 yr from the present will be 25–40 TW compared with about 8 TW at the present day. Three energy supply sources could be developed on a large enough scale to satisfy a demand of this magnitude: solar and nuclear energy and fossil fuels. The potential climate impact of the large-scale deployment of solar energy conversion systems has not been evaluated in detail. Solar thermal electric conversion systems could impact climate through large-scale changes in the energy balance at the earth's surface, in the surface roughness and in the surface wetness. Photovoltaic conversions could impact climate by acting as a local heat source. Ocean thermal electric conversion systems would have their main impact through changes in ocean surface temperature, but could also interfere with major ocean currents and have an impact through release of CO2 into the atmosphere or albedo changes, for example. The cultivation of plants for biomass conversion systems could influence climate through causing large-scale changes in the surface characteristics. The biomass conversion could also impact climate through releases of gases and particulate matter into the atmosphere. Through the use of climate models and observational studies, these impacts should be studied in more detail. In the meantime, the climate constraint should be kept in mind during the development of energy policy and the policies should be kept flexible at the present time until some of the uncertainties about the climate system have been resolved.