Global warming is the warming near the earth's surface that results when the earth's atmosphere traps the sun's heat. The earth is getting warmer. The changes are small, so far, but they are expected to grow and speed up. Within the next fifty to one hundred years, the earth may be hotter than it has been in the past million years. As oceans warm and glaciers melt, land and cities along coasts may be flooded. Heat and drought may cause forests to die and food crops to fail. Global warming will affect weather everywhere, plants and animals everywhere, people everywhere; humans are warming the earth's atmosphere by burning fuels, cutting down forest, and by taking part in other activities that release certain heat trapping gases into the air.
One major cause of global warming is the use of fossil fuels. Fossil fuels like coal, oil, and natural gas that were formed from the remains of plant material deposited during the earth's carboniferous period. We have known for only a few thousand years that coal, oil, and natural gas can be burned to provide energy. It was not until the mid-1800s, however, that we began to burn very large quantities of these fossil fuels. The worldwide consumption of fossil fuel has increased dramatically.
Climate scientists agree that the global average surface temperature has risen over the last century. Within this general agreement, some individual scientists disagree with the scientific consensus that most of this warming is attributable to human activities. The scientific consensus was summarized in the 2001 Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) as follows:
1. The global average surface temperature has risen 0.6 ± 0.2 °C since the late 19th century, and 0.17 °C per decade in the last 30 years.
2. "There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities", in particular emissions of the greenhouse gases carbon dioxide and methane.
3. If greenhouse gas emissions continue the warming will also continue, with temperatures projected to increase by 1.4 °C to 5.8 °C between 1990 and 2100. Accompanying this temperature increase will be increases in some types of extreme weather and a projected sea level rise of 9 cm to 88 cm, excluding "uncertainty relating to ice dynamical changes in the West Antarctic ice sheet". On balance the impacts of global warming will be significantly negative, especially for larger values of warming.
Those listed here have, since the Third Assessment Report of the IPCC, opposed at least one of these principal conclusions. Inclusion is based on specific, attributable statements in the individual's own words, and not on listings in petitions or surveys. For the purpose of this list a "scientist" is an individual who has published at least one peer-reviewed article during their lifetime in the broadly-construed area of natural sciences, though not necessarily in recent years nor in a field relevant to climate.
