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).
Digging in the Clay 
The warming effect of CO2 is logarithmic, and at current concentrations is become effectively asymptotic, so the greatest proportion of its possible warming effect has already occurred. Hence it is perhaps worth pointing out that without the necessary water vapour feedback the whole CAGW hypothesis is dead in the water as without this feedback the CO2 alone is incapable of producing anything approaching the necessary degree of warming.
The analyses of the NASA NVAP data show no evidence whatsoever for an increase in atmospheric water vapour, in fact Solomon et al indicates that in the decade post-2000 stratospheric water vapour actually declined ~10%.
http://www.climate4you.com/GreenhouseGasses.htm
http://onlinelibrary.wiley.com/doi/10.1029/2012GL052094/full
https://www.sciencemag.org/content/327/5970/1219.abstract
He does plan to mention the logarithmic effect, however it will go over the heads of the majority who don’t have some physics or chemistry knowledge, and water vapour feedback is a level of complication too far for an essentially lay audience. It’s a delicate balance. Yes there are some in the audience who would get that, but if you start to present too many ideas you will challenge even those who are following you to keep up and those who aren’t will just switch off.
Verity
Been involved with other things in this paddock so haven’t been watching. Good to see you back.
In agricultural extension I’ve seen that sometimes the best way of getting a message across doesn’t have to involve the best Queen’s English.
So,- how to explain exponential effect to such an audience?
Via an airforce song
Exponential up
“It started with three
Now there’s millions on me
How I’d like to get ’em wit hmy crab lotion”
Exponential down – hopefully when the lotion works.
Adapt if appropriate
Well in terms of being ‘back’ I’m trying, but there are so many other things vying for my attention these days…
The idea that CO2 has a logarithmic effect on global temperature was first stated by Svante Arrhenius in 1896.
Temperature Anomaly = ΔT = A * log2 ([CO2]/280)……..Where A is a constant representing K/Doubling of [CO2].
Using this equation one can explain the last seven glaciations covering a period of 850,000 years in terms of [CO2] simply by setting:
A = 16 K/doubling.
The same equation can explain the temperature variations over the last 150 years by setting:
A = 1.6 K/doubling.
There is a much more plausible theory to explain the correlation between temperature and [CO2] based on Henry’s law:
there is a new posting at http://www.ecofascism.com containing a list of 356 climate sceptical and/or enviro-critical websites plus additional info on the enviro-critical movement and its funders.
I don’t like the title of the site. Too black and white. The actual link that lists the websites is: http://www.ecofascism.com/article33.html
Twenty years ago we were told that the concentration of CO2 in the atmosphere would rise owing to the burning of fossil fuels. Even though the burning of fossil fuels is tiny compared to natural processes I think the “Warmists” are right………..humans are causing [CO2] to rise monotonically.
Natural processes produce and consume 20 times more CO2 than fossil fuels account for. However the natural processes have a net balance that is close to zero so the relatively small amount of CO2 from burning fossil fuels has a significant effect.
The next link in the chain of causation is not just weak……it is broken. Warmist theory predicts that temperature will rise as CO2 rises. The predicted warming simply has not happened over the last 19 years. The Warmists have tacitly admitted this because they no longer talk about “Global Warming”………today they threaten us with “Climate Change” which is a 100% certainty.
“Climate Change” has nothing to do with science because it is a hypothesis that cannot be tested by experiment or measurement. It is a meaningless concept designed to support a political agenda.
@Verity,
The benefits of CO2 are like an elephant in the room that Warmists try to ignore. They can’t risk an open debate as the benefits overwhelm the disadvantages that they claim:
Click to access benefits-of-co2.pdf
There is so much to say on the matter, but it has all been said before. It gets so stale that it is harder and harder to keep on countering the silliness.
Good to see you back in the saddle Verity.
The shortest way to debunk cagw theory, or at least put questions into the minds of an audience, is to point out that for agw to become cagw relies on there being net positive feedbacks to any warming created by CO₂ emissions. As the sign, or even the presence, of feedbacks was only ever an assumption on the part of cagw proponents, and has not been demonstrated, the whole theory collapses. Indeed, as a simple test of logic shows, feedbacks must be negative, as if they were positive the Earth would either be in a state of permanent ice ball or the alarmists predictions would have come to pass millennia ago and we’d all have been burned to a crisp.
Well, as I replied to Another Ian… I am trying.