Most of the observed temperature increases since the middle of the 20th century was caused by the increasing concentration of greenhouse gases (GHGs) due to the human activities such as fossil fuel burning and deforestation. The Intergovernmental Panel on Climate Change predicts global temperature change of 1.4-5.8oC will be caused by global warming from 1990-2100. Global warming projections by different organizations. Source: Special Report on Emissions Scenarios
