Mark Walport's staff have kindly made available the slides he used in Glasgow. They can be seen here.
As I have suggested previously, the talk was a recitation of the standard case for alarm, but there were many aspects of it that piqued my interest. For example, I noted that while warming up to the first slide he spoke about energy security first, before moving on to climate. Later on in the talk he spoke of the three lenses through which the climate problem had to be viewed and the first of these was again energy security. Is this a new tack? Are backsides starting to be covered? Perhaps.
Throughout the talk, I came away with the feeling that I was being sold something rather than being informed about the realities of climate science. With the climate records so noisy (see below), detection of significant changes is very hard and the predictions of temperature rise and sea-level rise and weather extremes and all the rest of it are therefore based almost entirely on GCMs. Yet where was this fact related to the audience and where was the discussion of the reliability of the models? Talking of an inability to predict the future with "perfect precision" (I think these were the words used) didn't do it for me.
This is the dilemma for the chief scientist. If the hypothesis of catastrophic global warming holds up it's a big deal. CSAs therefore want to push the public into getting behind the policy responses. But the public are not stupid and they know that they are not hearing the story warts and all and until they do they will harbour doubts. But if they are told the truth warts and all they are hardly going to be convinced that there is a cast-iron case. So we get a sales pitch and much crossing of the fingers and the problems with the models are pushed under the carpet.
A few comments on individual slides follow.
The climate science stuff begins at slide 13, with the standard HadCRUt4 graph and its decadal averages. The slide is entitled "Warming of the climate is unequivocal". To my mind this title falls into the category of "true but misleading". Yes the planet has warmed, but almost anyone seeing this slide might assume that we have therefore detected anthropogenic global warming. Since it seems that both sceptics and mainstream scientists seem to agree that the warming to date is indistinguishable from natural variability I think a balanced view on the science would incorporate this observation.
Slide 14 suggested that observations of the climate system are all telling the same story - surface temperatures up, ocean heat up, sea levels up, glaciers down, snow cover down and, erm, sea ice down. Readers here don't need to be told that the last of these is not true, and it must be doubtful whether it is possible to demonstrate a statistically significant change in the others. The question of what meaning can be attached to a group of statistically insignificant trends is an interesting one that I hope Doug Keenan is going to write about for me.
Slide 15, on ocean heat content is interesting, showing a clear pause in the rise at around 2005. I was struck by the comparison with slide 19, which shows no such pause.
Slide 24 says that dry regions of the Earth are going to get drier and wet regions are going to get wetter. It's interesting to compare this statement to the IPCC Summary for Policymakers (Fig SPM.8), which suggests that by the end of the century, many dry regions will have become much wetter - in particular Australia and the Sahara. At the end of the day though, we should observe that the ability of climate models to predict precipitation is even worse than their ability to predict temperature changes. In terms of the government chief scientist informing the public rather than selling them something, it would be fairer to say "we have no idea what effect a rise in global temperature would have on rainfall".
;)
Left: RCP2.6; Right: RCP8.5Slide 28 says we will see more damaging weather extremes. Climate models for years have said we are going to see increases in numbers and intensity of hurricanes, predictions that were closely followed by a drought in hurricane activity. This being the case, I would say it is incumbent on the chief scientist to express a little bit of doubt about such predictions. This again is sales pitch rather than dispassionate analysis.
Slide 34 reproduces AR5's Figure SPM.10, but leaves out the all-important caption that shows that the "historical" figures are not actually observations but a model hindcast. This was discussed in a comment thread at BH last year and, as Clive Best has observed you get a rather different story if you include the real observations.