Scientific consensus on climate change

There is scientific consensus that the Earth has been consistently warming since the start of the Industrial Revolution, that the rate of recent warming is largely unprecedented, and that this warming is mainly the result of a rapid increase in atmospheric carbon dioxide (CO2) caused by human activities. The human activities causing this warming include fossil fuel combustion, cement production, and land use changes such as deforestation, with a significant supporting role from the other greenhouse gases such as methane and nitrous oxide. This human role in climate change is considered "unequivocal" and "incontrovertible". Nearly all actively publishing climate scientists say humans are causing climate change. Surveys of the scientific literature are another way to measure scientific consensus. A 2019 review of scientific papers found the consensus on the cause of climate change to be at 100%, and a 2021 study concluded that over 99% of scientific papers agree on the human cause of climate change. The small percentage of papers that disagreed with the consensus often contained errors or could not be replicated.

The evidence for global warming due to human influence has been recognized by the national science academies of all the major industrialized countries. In the scientific literature, there is a very strong consensus that global surface temperatures have increased in recent decades and that the trend is caused by human-induced emissions of greenhouse gases. No scientific body of national or international standing disagrees with this view. A few organizations with members in extractive industries hold non-committal positions, and some have tried to persuade the public that climate change is not happening, or if the climate is changing it is not because of human influence, attempting to sow doubt in the scientific consensus.

Existence of a scientific consensus

Studies of the scientific opinion on climate change have been undertaken since the 1970s, and they have been establishing widespread consensus since the 1990s, with the level of agreement increasing over time. Individual scientists, universities, and laboratories contribute to the scientific opinion on climate change via their peer-reviewed publications, while the scientific bodies of national or international standing summarise the areas of collective agreement and relative certainty in synthesis reports. Examples of such reports include or the 2004 Arctic Climate Impact Assessment from the International Arctic Science Committee and the governments of the Arctic Council, or the United States' National Climate Assessment, which has been released periodically since 2000 under the auspices of the United States Global Change Research Program. The fourth NCA, released in 2017, involved the efforts of thirteen federal agencies, led by the National Oceanic and Atmospheric Administration (NOAA), and around "1,000 people, including 300 leading scientists, roughly half from outside the government."

The Intergovernmental Panel on Climate Change (IPCC) had been formed by the United Nations in 1988, and it presents reports summarizing the strength and extent of consensus on climate change and its numerous aspects to the member states of the United Nations, with the major reports released at 5-to-7-year intervals starting from 1990. In 2001, science academies from 17 countries (Australia, Belgium, Brazil, Canada, China, France, Germany, India, Indonesia, Ireland, Italy, Malaysia, New Zealand, Sweden, Trinidad, Turkey and the United Kingdom) made a joint statement endorsing the work of IPCC. They concurred that the temperatures are rising and will continue to rise due to human activities, and also stressed the importance of cutting greenhouse gas emissions, concluding that "Business as usual is no longer a viable option". It is also notable for being one of the first statements to explicitly use the term "consensus". In 2005, another joint statement from the science academies of major countries (Brazil, Canada, China, France, Germany, India, Italy, Japan, Russia, United Kingdom and the United States) referred to the conclusions of the IPCC as "the international scientific consensus", and urged prompt action on both climate change mitigation and climate change adaptation. Elsewhere around the world, other organizations to have referred to the scientific consensus include Network of African Science Academies in 2007, and the International Union for Quaternary Research in 2008. In 2013, a study which found that out of over 4,000 peer-reviewed papers on climate science published since 1990, 97% agree, explicitly or implicitly, that global warming is happening and is human-caused. Surveys of scientists' views on climate change – with a focus on human caused climate change – have been undertaken since the 1970s. A 2016 reanalysis confirmed that "the finding of 97% consensus [that humans are causing recent global warming] in published climate research is robust and consistent with other surveys of climate scientists and peer-reviewed studies." A 2019 study found scientific consensus to be at 100%, and a 2021 study found that consensus exceeded 99%.

Consensus points

The scientific consensus regarding causes and mechanisms of climate change, its effects and what should be done about it (climate action) is that:

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