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The problem of climate change

Since the mid-1800s, scientists have understood in principle that greenhouse gases (GHGs) such as carbon dioxide (CO2) could cause atmospheric warming.2 Widespread scientific agreement that climate change was in fact occurring emerged in the late 1980s. In 1988 the Intergovernmental Panel on Climate Change (IPCC) was founded by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) to provide governments at all levels with scientific information to develop climate policies. The IPCC does not conduct its own research, but through assessments of existing research identifies the strength of scientific consensus globally. By 1991, two-thirds of earth and atmospheric scientists accepted the idea of anthropogenic global warming.3 By 1995, the IPCC concluded that “the balance of evidence suggests that there is a discernible human influence on global climate.”4 And in its Sixth Assessment Report in 2021, the IPCC stated that “it is unequivocal that human influence has warmed the atmosphere, ocean and land.”5