| Global warming is the increase in the average | | | | continue for more than a millennium even if |
| temperature of the Earth's near-surface air and | | | | greenhouse gas levels are stabilized. This reflects |
| oceans in recent decades and its projected | | | | the large heat capacity of the oceans. |
| continuation. | | | | An increase in global temperatures can in turn |
| Global average air temperature near the Earth's | | | | cause other changes, including sea level rise, and |
| surface rose 0.74 ± 0.18 °C (1.3 ± | | | | changes in the amount and pattern of |
| 0.32 °F) during the past century. The | | | | precipitation. There may also be changes in the |
| Intergovernmental Panel on Climate Change | | | | frequency and intensity of extreme weather |
| (IPCC) concludes, "most of the observed increase | | | | events, though it is difficult to connect specific |
| in globally averaged temperatures since the | | | | events to global warming. Other effects may |
| mid-20th century is very likely due to the | | | | include changes in agricultural yields, glacier retreat, |
| observed increase in anthropogenic greenhouse | | | | reduced summer streamflows, species extinctions |
| gas concentrations," which leads to warming of | | | | and increases in the ranges of disease vectors. |
| the surface and lower atmosphere by increasing | | | | Remaining scientific uncertainties include the exact |
| the greenhouse effect. Natural phenomena such | | | | degree of climate change expected in the future, |
| as solar variation combined with volcanoes have | | | | and how changes will vary from region to region |
| probably had a small warming effect from | | | | around the globe. There is ongoing political and |
| pre-industrial times to 1950, but a cooling effect | | | | public debate regarding what, if any, action should |
| since 1950. The basic conclusions have been | | | | be taken to reduce or reverse future warming or |
| endorsed by at least 30 scientific societies and | | | | to adapt to its expected consequences. Most |
| academies of science, including all of the national | | | | national governments have signed and ratified the |
| academies of science of the major industrialized | | | | Kyoto Protocol aimed at combating greenhouse |
| countries. The American Association of Petroleum | | | | gas emissions. |
| Geologists is the only scientific society that | | | | Terminology |
| rejects these conclusions, and a few individual | | | | The term "global warming" is a specific example |
| scientists also disagree with parts of them. | | | | of the broader term climate change, which can |
| Climate models referenced by the IPCC project | | | | also refer to global cooling. In common usage the |
| that global surface temperatures are likely to | | | | term refers to recent warming and implies a |
| increase by 1.1 to 6.4 °C (2.0 to 11.5 °F) | | | | human influence. The United Nations Framework |
| between 1990 and 2100. The range of values | | | | Convention on Climate Change (UNFCCC) uses |
| reflects the use of differing scenarios of future | | | | the term "climate change" for human-caused |
| greenhouse gas emissions and results of models | | | | change, and "climate variability" for other changes. |
| with differences in climate sensitivity. Although | | | | The term "anthropogenic climate change" is |
| most studies focus on the period up to 2100, | | | | sometimes used when focusing on human-induced |
| warming and sea level rise are expected to | | | | changes. |