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