Posted on 30 September 2013 by John Cook

I recently presented a public talk at the new Global Change Institute living building on the topic of scientific consensus. Specifically, the talk was titled Closing the consensus gap a key to increasing support for climate action. I go into why there is a scientific consensus on human-caused global warming, explain the research in our consensus paper published in Environmental Research Letters and answer 5 criticisms of our paper. Here's the full video which you can also view at the GCI website (with details of the powerpoint slides to follow):

The talk featured a number of new powerpoint slides which anyone is welcome to reuse - here is the full Powerpoint file (5.5Mb). For example, I begin the talk by talking about the greenhouse effect, adapting the excellent graphics created by SJI Associates for theconsensusproject.com:

Discussion of the mechanism of the greenhouse effect led naturally into discussion of the many independent human fingerprints being observed in our climate system:

Normally when I talk about the "Consensus Gap", the discrepancy between the 97% consensus and the public perception of consensus, I use a histogram of the public response to the question "how many climate scientists agree that humans are causing global warming?" Now I have a lot of sentimental attachment to my histogram. But for some reason, everyone I show the graph to responds with a universal "meh". There's just not a lot of histogram love in the room. So I've capitulated to popular opinion (grumbling every step of the way) and gone with ordinary piecharts which in my opinion loses a lot of valuable information:

Why is there such a significant consensus gap? I go on to talk about the two decade campaign to manufacture doubt about scientific consensus, using a timeline created in collaboration with SkS artist JG:

Lastly, and this is probably what will interest people most, I address some of the attacks directed towards our consensus paper. Interestingly, the attacks are consistent with the five characteristics of consensus denial:

• Fake debate
• Logical Fallacies
• Impossible Expectations
• Cherry Picking
• Conspiracy Theories

I'll leave you to watch the talk and view the responses but I will tease you with what is my favourite conspiracy theory regarding our consensus paper to date:

In the subsequent slide, I examine some of the impressive achievements of the journal Environmental Research Letters, which demonstrates the implausibility of this kind of conspiratorial thinking.

Note: all my slides are available as Powerpoint slides (5.5Mb) and everyone is welcome to republish our graphics.