How would you present climate change from a sceptical viewpoint to a lay audience in a 20 minute talk? That’s what a friend has volunteered to do and recently asked for my help. In particular, could I provide some illustrations? The audience is likely to be mostly middle-aged men of varied backgrounds, most of whom will have given the subject little thought other than absorbing media coverage. I do know one person who will attend and that person is an environmental professional, a believer in CAGW, but is usually open-minded and definitely of a sceptical disposition as far as non-climate things go.
After the initial “yes – of course!”, I began to wonder where to start… And the more I thought about it the more I found I would want to include. Keep it simple, I thought, but my friend has very definite ideas of what he wants to cover. He had written out a draft of what he planned to say, which he ran through.
His starting point was the Sun, the relative sizes of Earth and the solar system. After that he intended to cover the temperature of Earth due to the greenhouse effect, Milancovitch Cycles, CO2 in ice cores over the last half a million years, and then the relative percentages and volume of CO2 relative to other gases in the atmosphere. I thought this initially too complex (and a bit rambling), but we managed to pare it down to simple concepts and it provided a good solid introduction.
He then planned to talk about the natural sources of CO2 and the relative sizes of fluxes, sources and sinks. For illustrative purposes we decided on pictures of sources and sinks and one of the simpler IPCC diagrams. At this stage he planned to discuss the relative sizes of each of these sources and sinks, how they are measured and our uncertainties, but has settled for saying that science is always refining the estimates.
Then he came to the effects of CO2 on plant growth. That’s something I’d not really looked at much and it sent me into a frenzy of reading (more on that in future). We came up with a lovely set of images telling that part of the story.
At this point it seemed useful to sum up. Earth is warming and carbon dioxide is increasing; the debate is about how much and why:
- How much of the warming is due to natural changes and how big a role does CO2 play in warming Earth?
- Is the increased CO2 likely to have a big effect (catastrophic) or small effect (benign, possibly overall beneficial)
That introduced the political side, wondering how many would have seen Al Gore’s An Inconvenient Truth. We discussed how to cover the “97% consensus” issue and decided it was probably best to describe Cook et al‘s methodology and Legates’ rebuttal. With plenty else to say about politics and media bias it seemed a good idea to move on, perhaps revisiting it as a question at the end for discussion.
The last point was to be about the surface temperature record. As huge fans of Anthony Watts’ posts “How not to measure temperature…” we both wanted show that temperature measurement was more complex and contentious than most people would think. A few examples of good and badly sited weather stations would suffice along with some of the effects of adjustments – for shock value while acknowledging that some adjustment is needed.
I should say at this point that we have agreed that the point of the talk should be that people should not just accept blindly what is presented in the media, but should seek alternative views and think for themselves. The information will be presented as the thoughts of someone who did just that, hoping that the group will then ‘discuss over food’.
Will let you know the feedback (I am not invited).