As an independent test of the measured consensus, we also emailed over 8,500 authors and asked them to rate their own papers using our same categories. The most appropriate expert to rate the level of endorsement of a published paper is the author of the paper, after all. We received responses from 1,200 scientists who rated a total of over 2,100 papers. Unlike our team's ratings that only considered the summary of each paper presented in the abstract, the scientists considered the entire paper in the self-ratings.
The 97% Consensus Results
Based on our abstract ratings, we found that just over 4,000 papers expressed a position on the cause of global warming, 97.1% of which endorsed human-caused global warming. In the self-ratings, nearly 1,400 papers were rated as taking a position, 97.2% of which endorsed human-caused global warming.
We found that about two-thirds of papers didn't express a position on the subject in the abstract, which confirms that we were conservative in our initial abstract ratings. This result isn't surprising for two reasons: 1) most journals have strict word limits for their abstracts, and 2) frankly, every scientist doing climate research knows humans are causing global warming. There's no longer a need to state something so obvious. For example, would you expect every geological paper to note in its abstract that the Earth is a spherical body that orbits the sun?
This result was also predicted by Oreskes (2007), which noted that scientists
"...generally focus their discussions on questions that are still disputed or unanswered rather than on matters about which everyone agrees"
However, according to the author self-ratings, nearly two-thirds of the papers in our survey do express a position on the subject somewhere in the paper.
We also found that the consensus has strengthened gradually over time. The slow rate reflects that there has been little room to grow, because the consensus on human-caused global warming has generally always been over 90% since 1991. Nevertheless, in both the abstract ratings and self-ratings, we found that the consensus has grown to about 98% as of 2011.
The 97% Consensus Results
Based on our abstract ratings, we found that just over 4,000 papers expressed a position on the cause of global warming, 97.1% of which endorsed human-caused global warming. In the self-ratings, nearly 1,400 papers were rated as taking a position, 97.2% of which endorsed human-caused global warming.
We found that about two-thirds of papers didn't express a position on the subject in the abstract, which confirms that we were conservative in our initial abstract ratings. This result isn't surprising for two reasons: 1) most journals have strict word limits for their abstracts, and 2) frankly, every scientist doing climate research knows humans are causing global warming. There's no longer a need to state something so obvious. For example, would you expect every geological paper to note in its abstract that the Earth is a spherical body that orbits the sun?
This result was also predicted by Oreskes (2007), which noted that scientists
"...generally focus their discussions on questions that are still disputed or unanswered rather than on matters about which everyone agrees"
However, according to the author self-ratings, nearly two-thirds of the papers in our survey do express a position on the subject somewhere in the paper.
We also found that the consensus has strengthened gradually over time. The slow rate reflects that there has been little room to grow, because the consensus on human-caused global warming has generally always been over 90% since 1991. Nevertheless, in both the abstract ratings and self-ratings, we found that the consensus has grown to about 98% as of 2011.