There is overwhelming scientific agreement that climate change is both real and is mostly caused by human activity, especially the burning of fossil fuels and deforestation. Reviews of published research consistently find that more than 97 percent of climate scientists now attribute recent global warming mostly to human causes, and several analyses even place the consensus above 99 percent.* Moreover, leading scientific institutions and national academies, including NASA (United States space agency) and the Intergovernmental Panel on Climate Change (IPCC), have confirmed this conclusion through independent assessments.
This consensus is based on multiple types of evidence, including direct temperature measurements, ocean heat, melting ice, rising sea levels, satellite observations and the physics of greenhouse gases. All of these fit together to show a highly consistent pattern of warming resulting from greenhouse gas emissions rather than natural causes.
The basic physics of greenhouse gases is simple: increases in these gases in the atmosphere trap more heat near the earth's surface. This has been confirmed in both laboratory and atmospheric studies, and the observed warming has been consistent with the predictions of this theory.
Moreover, climate models developed decades ago successfully predicted both the magnitude and the spatial distribution of the warming. This remarkable agreement makes climate science one of the most rigorously validated fields of research. Although scientists continue to refine their projections of localized effects, the rate of future warming and feedback effects such as ice loss or cloud behavior, none of these contradict the fundamental conclusion that human activity has been the dominant cause of recent climate change.
The greenhouse effect has been understood in a basic form for more than two hundred years, following its first proposal by French mathematician and physicist Joseph Fourier in 1824. The 1970s saw major refinement of quantitative understanding, including measuring the role of carbon dioxide, and constructing theoretical climate models. The 1979 Charney Report concluded that doubling atmospheric carbon dioxide would likely produce substantial warming, but it still treated large-scale climate change as a serious risk rather than a confirmed fact.
During the 1980s, improved observations and computer modeling boosted confidence in these predictions. Major meetings, such as the 1985 Villach Conference, issued warnings that significant human-caused warming was likely. This was followed by the creation of the IPCC in 1988, which established a structured international process for assessing climate research.
By the mid-1990s, agreement among scientists about human influence on the climate had become very strong, and by the early 2000s, especially following the 2007 IPCC Fourth Assessment Report, the consensus was widely recognized as overwhelming. Moreover, it has strengthened even further through subsequent research over the past two decades.
That human activity is the dominant cause of climate change today ranks among the most robust of scientific consensuses in any field, comparable to those regarding evolution, plate tectonics (continental drift) and the linkage between smoking and lung cancer. In each of these cases, diverse lines of evidence have converged on the same conclusion, which has been repeatedly tested and confirmed over many decades.
However, as is often the case regarding scientific issues, public understanding of climate change and the urgency for taking strong action to combat it has lagged behind expert consensus. This gap, which persists to varying extents around the world, is largely because of the influence of politicians, economic interests and mass media as well as to differences in access to education and reliable information.
Scientific research and politics operate on very different incentives and rules. Scientific conclusions are based on evidence and subject to peer review. They must be supported by data and open to independent replication, and false claims can damage reputations and destroy careers.
Politicians, in contrast, are largely motivated by elections, party goals and donor interests, which can reward loyalty and adherence to ideology. Thus they sometimes take positions aligned with ideological or industrial interests, which can diverge from scientific findings and often favor short-term gains over long-term evidence regarding climate, and other environmental, risks.
_______
*For example, meta-analyses of published studies by Mark Lynas et al. (2021) published in Environmental Research Letters and research led by John Cook, have found that over 97 percent to 99 percent of climate scientists agree that human activities are driving global warming. John Cook is a Senior Research Fellow with the Melbourne Centre for Behaviour Change at the University of Melbourne and is a leading expert in the cognitive psychology of climate science denial. Cook and others have pointed out that as expertise in climate science increases, so does the consensus among scientists on human-caused warming, rising from 97 percent to more than 99 percent.