Opinion, Berkeley Blogs

The story of a presidential tweet

By Daniel Kammen

We generally complain that action on climate change is mired in polarized partisan politics and thus nothing can be done. True to an extent, but let's hold on a bit.

In terms of generating important discussion about the clarity that exists around the conclusion that the scientific debate over climate change as an anthropogenic process is over, the political bully pulpit can be incredibly powerful.

A case in point is the paper published last week in Environmental Research Letters, where I am the Editor-in-Chief: "Quantifying the consensus on anthropogenic global warming in the scientific literature" John Cook, of the Global Change Institute, University of Queensland, Australia, was lead author of the paper, which begins with this abstract:

We analyze the evolution of the scientific consensus on anthropogenic global warming (AGW) in the peer-reviewed scientific literature, examining 11,944 climate abstracts from 1991–2011 matching the topics "global climate change" or "global warming." We find that 66.4 percent of abstracts expressed no position on AGW, 32.6 percent endorsed AGW, 0.7 percent rejected AGW and 0.3percent were uncertain about the cause of global warming. Among abstracts expressing a position on AGW, 97.1 percent endorsed the consensus position that humans are causing global warming. In a second phase of this study, we invited authors to rate their own papers. Compared to abstract ratings, a smaller percentage of self-rated papers expressed no position on AGW (35.5 percent.) Among self-rated papers expressing a position on AGW, 97.2 percent endorsed the consensus. For both abstract ratings and authors' self-ratings, the percentage of endorsements among papers expressing a position on AGW marginally increased over time. Our analysis indicates that the number of papers rejecting the consensus on AGW is a vanishingly small proportion of the published research.

The paper came out, and President Barack Obama's Twitter account weighted in:

‏@BarackObama: Ninety-seven percent of scientists agree: ‪#climate change is real, man-made and dangerous.

Read more: ‪http://OFA.BO/gJsdFp 

That high-profile tweet (not directly from the president, but like all his tweets, from the campaign group formed to support his political agenda) drove a wave of attention to the research. Follow-on tweets came from Vice-President Al Gore and U. S. Congressman Henry Waxman.  Television coverage followed in: ABC Lateline, Al Jazeera (Inside Story), CNN International, Democracy Now, and NRK. At last count there were over 200 newspaper and magazine pieces, and a number of radio segments.  At last count there were several hundred blog posts on the findings of this paper and the Obama Tweet.  A link to the ever-growing set of media coverage is: http://sks.to/tcpmedia

The article has been downloaded over 21,600 article downloads in just a few days of having the paper published online.

What this story highlights – beyond the excellent data collection, analysis and scholarship in the paper itself – is the value of thoughtful comments and recognition of these findings.

Daniel M. Kammen is the Distinguished Professor of Energy at the University of California, Berkeley, where he founded and directs the Renewable and Appropriate Energy Laboratory (http://rael.berkeley.edu).   He is a coordinating lead author for the Intergovernmental Panel on Climate Change, which shared the 2007 Nobel Peace Prize, and serves as the lead scholar for the Fulbright NEXUS program in energy and climate for the U. S. Department of State.


John Cook, Dana Nuccitelli, Sarah A Green, Mark Richardson, Bärbel Winkler, Rob Painting, Robert Way, Peter Jacobs and Andrew Skuce (2013) “Quantifying the consensus on anthropogenic global warming in the scientific literature”, Environmental Research Letters, 8 (2). http://iopscience.iop.org/1748-9326/8/2/024024/article