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The story of a presidential tweet

Daniel Kammen, Class of 1935 Distinguished Professor of Energy | May 29, 2013

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:

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 (   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).

Comments to “The story of a presidential tweet

  1. Dr. Kammen, I’m curious as to why you have not responded to Jose Duarte regarding his scathing criticism of Cook’s (et al) unscientific and quite fraudulent approach to this magical 97%. (

    I would expect one who calls himself a scientist to have the integrity to investigate such an issue.

  2. I see no comment from you on the falsehood in the Presidential tweet—the 97% said nothing about AGW being “dangerous.”

    An innocent oversight, no doubt. Scientists don’t tolerate falsehoods. You were a scientist at one point, were you not Prof Kammen?

  3. Mr John Cook never corrected the ‘misinformation’ in the Obama tweet that he likes to promote heavily. A real climate scientist tried to..

    Barack Obama
    @BarackObama Ninety-seven percent of scientists agree: #climate change is real, man-made and dangerous. Read more: http://OFA.BO/gJsdFp

    @BarackObama Actually that paper didn’t say ‘dangerous’. NB I *do* think #climate change poses risks – I just care about accurate reporting!

    This is Professor Richard Betts – Chair in Climate impacts

  4. The Cook et al paper did not show 97% of scientists agree “‪#climate change is real, man-made and dangerous”. It didn’t do that and nor was it in its methodological scope to show that.

    You say above:

    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.

    Since the paper does not support this exaggerated statement of a powerful politician, yet academic media pundits (such as yourself) and the papers authors do not correct the politician but rather merely echo his exaggeration, it would seem to this member of the public that by “clarity” you mean “the kind of political exaggeration I like”.

    This crypto-political behaviour of academics is not hard to demonstrate can only increase public cynicism and distrust of climate related academia.

    When you talk of action being “mired in polarized partisan politics” do you not realise you are guilty of playing partisan politics using the guise of academic objectivity?

  5. Science is not determined by consensus, so the percentage is irrelevant.
    With China starting up 1 Coal Fired power Plant per week, the efforts in the US to reduce CO2 emissions are also irrelevant. Fracking will allow the US to produce cheap Natural Gas which will reduce CO2 emissions, but will greatly reduce the likelihood that expensive alternative energy projects will proceed.

  6. I’m not sure if there is any way other then controlling on our daily lives pollution activities.

      • “…Controlling our pollution is surely key…”

        This statement demonstrates part of the problem in which you use whom you quote and they play an important and disingenuous part.
        Here, you deliberately conflate “pollution” with “climate change” – a position which is taken by many fraudulent “warming” promoters.
        OF COURSE we must address – and stop pollution – but Obama’s very unscientific tweets (not the one above) also conflate asthma with global warming; and presents its epidemiology as proof the CO2 is a “problem” which needs trillion$ spent on its eradication.
        CO2 is a greenhouse gas, to be sure – but nowhere near as strong as water vapour, which is present at levels unto 30,000ppm… why should CO2 be “dangerous,” as Obama quotes, quite incorrectly from “studies” which claim no such thing.
        CO2 is an essential, vital gas, without which life would not exist. Please notice that the term “organic” means “carbon-based.” Plants need carbon dioxide at a level of AT LEAST 150ppm – just to survive. The ~400ppm we see now is still less than the probable optimum of ~2000ppm, which is a demonstrable fact, and levels around 1000ppm are routinely used in greenhouses to boost plant growth.

  7. That is quite a large-scale question, but yes, there are cost-effective opportunities to move the clean energy economy along. There are many items that would go into a ‘to do’ list, including:

    – Implement PACE financing for residences and commercial properties. PACE is a simple municipal financing
    tool (see, e.g.: or that has been blocked by
    the Federal Housing Finance Agency for little or no good reason). With this lifted, property owners could
    borrow funds to do energy efficiency and renewable upgrades, then pay the city back. This increases the
    property value with a ‘green’ product.

    – Implement a federal renewable energy standard via a RPS (renewable energy portfolio standard) or a
    FIT (feed-in tariff)

    – Implement a carbon tax, and reinvest the funds. This could also be off-set with direct payments to lower-
    income citizens, and/or could be offset with a reduction in employment or other taxes and fees.

    • Thank you very much for your fast response Prof. Kammen, I greatly respect you experience, expertise and dedication to preventing global warming from getting beyond our control, but my question was obviously too brief and thus excluded some vital conditions that are imperative.

      Now that we have passed 400 ppm, “immediate implementation” means that the solutions must be politically, socially, scientifically and internationally feasible to achieve “Avoidance of Calamity” that the late Nature magazine editor Sir John Maddox documented in his book “What Remains to Be Discovered.”

      Will your solutions be implemented in time to protect acceptable quality of life for all future generations?

      If not, can university professors and scholars around the world join together to educate and motivate the people of the world to overcome our failures to meet the challenges of change so we can protect our future?

      • You are so right that the 400 ppm is just a number, but an important one!

        The short ‘early action’ set of policy steps needed that I listed above really all need to happen now (even better would have been a decade ago, of course!), but as Jim Hansen (now of Columbia U., formerly of NASA) notes, this is the decade…..

        • Excellent recommendations Prof. Kammen, who is the most highly respected international spokesperson to educate and motivate people around the world to achieve these goals?

          • HI Anthony,

            We will likely need a suite of spokes-people!

            Any of us can play that role …. but I think you are referring mainly to people who are already ‘public figures’. Politically, Chancellor Merkel did an excellent job in that role, as did UB Prime Minister Tony Blair for some time, as did Governor Schwarzenegger.

            Too few national leaders today are finding that this issue is either attracting enough attention, or that they can use it to leverage their image enough — all of which is a shame. A number of private sector leaders, however, are working on environmental issues, and this is an excellent change.

            Overall, though both political figures and corporate leaders do respond very well to voter (consumer) interest, so the more we ask for this issue to be a high priority the more it will be.

  8. Much more importantly Prof. Kammen, do you have a solution to save the human race from global warming chaos and unacceptable quality of life in this century, a solution that we can implement immediately?

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