Intergovernmental Panel on Climate Change

Intergovernmental Panel on Climate Change (IPCC), United Nations panel established by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) in 1988. Headquartered with the WMO in Geneva, Switzerland, the Intergovernmental Panel on Climate Change (IPCC) assesses peer-reviewed literature and industry practices to determine the impact of and possible responses to climate change associated with global warming. While it produces no research of its own, its members—divided into three working groups and a task force—assemble reports from hundreds of scientists and policymakers from around the globe. These are analyzed and distributed as special papers or as more-comprehensive assessment reports. In 2007 the IPCC shared, with Al Gore, the Nobel Peace Prize for disseminating knowledge about human-caused climate change.

Between 1990 and 2021 the IPCC released six assessment reports (AR1–AR6) and several special reports that described the current state of greenhouse gases (GHGs) in Earth’s atmosphere, trends in greenhouse gas emissions, and their likely effects on atmospheric processes, economies, and ecosystems. The reports also made projections using a suite of scientific modeling techniques to predict the state of several variables (average near-surface air temperatures, sea levels, average ocean pH, sea ice extent, drought frequency, etc.) out to the year 2100.

The special report released in 2018 noted that human beings and human activities are responsible for a worldwide average temperature increase of between 0.8 and 1.2 °C (1.4 and 2.2 °F) of global warming above benchmark averages—that is, average global temperature levels set before the start of the Industrial Revolution. However, since the fifth assessment report (AR5), published in 2014, all but a few nations are instituting carbon reduction plans as part of the Paris Agreement, which endeavours to keep global warming to 1.5 °C (2.7 °F) above preindustrial levels. The authors noted that they had high confidence that the world would reach 1.5 °C above benchmark averages sometime between 2030 and 2052 should carbon emissions continue at their present rate.

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Global warming policy: The IPCC and the scientific consensus

Released in 2021, the sixth assessment report (AR6) noted that human beings had produced an “unequivocal” influence over Earth’s climate system as human-generated GHGs have increased in Earth’s atmosphere. The report also revealed that global surface temperatures for the years 2000 to 2020 were 0.99 °C (1.8 °F) higher than benchmark averages and that since 1980 a succession of decadal global temperature averages had been higher than those measured in any preceding decade. These developments have driven glacial retreat, Arctic sea ice loss, and a poleward shift in the planet’s climate zones. The authors noted that even under the very low GHG emissions scenario (which assumed that GHG emissions stabilize and decline), global surface temperatures would reach 1.2–2.0 °C (2.1–3.6 °F) by 2050 before declining slightly to 1.0–1.8 °C (1.8–3.2 °F) above benchmark averages by 2100. However, under the intermediate scenario (which assumed that GHG emissions would remain steady), global surface temperatures would be expected to reach 2.0 °C (3.6 °F) by mid-century, later increasing to 2.1–3.5 °C (3.8–6.3 °F) by 2100.