Most climate scientists agree that rising temperatures are being caused by increasing concentrations of greenhouse gases (GHGs) in the earth’s atmosphere. Most of the increase in GHG concentrations is the result of emissions associated with human activities, such as burning fossil fuels (oil, coal, and natural gas), cutting down forests, and certain agricultural activities. Most climate scientists, including those working on the Intergovernmental Panel on Climate Change, believe that human activities are the principal causes of these changes.