Short answers, pulled from the story.
Among actively publishing climate scientists, surveys consistently show agreement of 97 percent or higher. A 2021 study by Krista Myers found that 100 percent of climate scientists with more than 20 peer-reviewed papers agreed that human activity is causing climate change, and 98.7 percent of all climate scientists in that survey agreed.
James L. Powell, a former member of the National Science Board, found that of 13,950 peer-reviewed articles on global warming published between 1991 and 2012, only 24 (less than 0.2 percent) rejected anthropogenic global warming. By 2017, combining five surveys covering 54,195 articles from 1991 to 2015, he calculated an average consensus of 99.94 percent.
Studies of scientific opinion on climate change began in the 1970s, with the National Defense University surveying 24 experts as early as 1978. Widespread consensus was being established by the 1990s, and the level of agreement has increased over time, reaching 100 percent in a 2019 review of papers published in the first seven months of that year.
Atmospheric carbon dioxide is now at its highest level in at least 2 million years, and possibly 3.2 million years. Methane and nitrous oxide have reached their highest concentrations in at least 800,000 years.
In the 2009 Doran and Zimmerman survey of 3,146 earth scientists, economic geologists showed the lowest agreement at 47 percent believing in significant human involvement, followed by meteorologists at 64 percent. The 2021 Myers study found scientists who identified Economic Geology as a field showed the lowest agreement at 84 percent, compared to 100 percent among high-expertise climate scientists.
In 2001, science academies from 17 countries including Australia, Brazil, China, India, and the United Kingdom jointly endorsed the IPCC's findings. They concluded that temperatures are rising and will continue to rise due to human activities, and stated that "Business as usual is no longer a viable option." The statement was among the first to explicitly use the term "consensus."