What Effect Do Greenhouse Gases Have on Climate?
Given the natural variability of the Earth s climate, it is difficult to determine whether any change can be attributed to human activity. Evidence accumulated by the Intergovernmental Panel on Climate Change (IPCC), which was established by the World Meterological Organization and the United Nations Environment Programme to assess the available scientific, technical, and socio-economic information regarding climate change, indicates that global mean surface air temperature has increased between approximately 0.3 and 0.6ºC (0.5 and 1.1ºF) since the late 19th century. Although there is considerable uncertainty about whether this temperature increase has been caused by anthropogenic greenhouse gas emissions, the IPCC has concluded that the balance of evidence suggests that there has been a discernible human influence on global climate. What Are the Sources of Greenhouse Gas Emissions? In the United States, nearly 85 percent of anthropogenic greenhouse gas emissions result from the burnin
