JohnH, just lobbed into this thread and found your comment to Kulu:

"Why, then, do you think that the IPCC dropped Mann’s hockey stick graph from its AR4 after having so enthusiastically adopted it for its first three assessment reports? It wouldn't have been because Mann's work didn't stand up to scientific scrutiny, would it?"

No, your answer to your own question is wrong.

Before I continue, just a minor quibble. The IPCC could NOT have "dropped Mann’s hockey stick graph from its AR4 after having so enthusiastically adopted it for its first three assessment reports" because Mann et al did not have the paper published till 1998.

While there were issues with the MBH98 paper, subsequent research to TAR using other data sets and sources reinforced the so called "hockey stick". There are now many more "hockey sticks" and are all included in the AR4 in Chapter 6 - if you would bother to look.

You are either exhibiting a lack of knowledge of the AR4 or are deliberately being obtuse (I will not accuse you of deliberatley lying, yet). Which is it?

Either way, this diminishes any credibility that you purport to have in your article or subsequent responses, in my opinion.

Oh yeah, John:

"Clean Coal" is a misnomer. But hey, throw some money at the technology (something could eventuate in a couple of decades) - it will placate the vested interest groups.

To be brutally honest, you can't shut down an industry like that overnight - for whatever reason.

Q&A

Whoops, you certainly have caught me out. I worked from memory on the inclusion of Mann’s hockey stick in IPCC’s assessment reports and ended up with a sloppy comment.

It appeared around six times, and quite prominently, in the TAR. But, without checking, I thought it had been dropped from AR4. Of course, you are right – it appears in AR4 in Figure 6-10 and is also incorporated in Box 6.4, Figure 1. However, it certainly doesn’t hold the same prominence as it did in TAR, which means, presumably, that it has lost its credibility.

Fault has been found with Mann’s work, as you acknowledge, but I’m unaware of any criticism of the numerous other hockey sticks, 12 in total. However, since all are based on proxy data sets, and are similar in form, it seems reasonable to view their validity with suspicion. When one considers the wide variation in results in Figure 6.10, graph to graph, and the mess in Box 6.4, Figure 1(a), it is really surprising that any firm conclusion could have been drawn from them.

I’m surprised that you question the credibility of my essay on “clean coal”. Where do you find it incredible? As to the various posts I have submitted, they relate to my sceptical position on AGW, and were incidental to the thrust of my essay. If certain individuals hadn’t been abusive, they would not have appeared. So what did you find wrong or whatever with my article?

I agree with the content of your second post.

No John, it hasn't lost its credibility. While it did have issues, the tenets contained within remain just as strong. The reason why the MBH98 stick doesn’t hold the same prominence in AR4 is because there is a preponderance of other evidence supporting the theory of AGW.

It seems you question the validity of all proxy reconstructions on the premise they have the same shape and form as Mann’s, notwithstanding they are arrived at from different data sets and sources.

Do you really think they haven’t been scrutinised, dissected and reviewed to the nth degree given the amount of flack Mann received?

Tell you what; get rid of them all, who needs past climate anyway. We can start afresh, measure all sorts of stuff from now on and in 100 yrs we will know if the trend is up or down.

John, you did have had some good things to say in your article, you just should have left out the last 3 paragraphs.

It’s like Al Gore, he had some good things to say about global warming – unfortunately, he marginalised a lot of people because of his political propaganda – albeit the substance of his message was correct.

Q&A

Visitors departed … now your post.

The first comment I will make relates to your first paragraph. “Theory of AGW” – yes, “theory”, because no proof has yet been provided.

You say that Mann’s hockey stick doesn’t hold the same prominence because of the preponderance of other evidence. Really? I suggest to you that, if the hockey stick was the answer to the IPCC’s prayers (and initially it was), then it would still have held pride of place in AR4.

I do question the validity of the other proxy reconstructions, even though they, presumably, are based on different data sets to Mann’s effort. For one thing, proxies, by definition, are estimations of temperature and therefore possess intrinsic errors – they are not thermometer readings.

You have only to look at the wide variation from one plot to another in the 12 curves shown in Figure 6.10 (b). Why is one curve, say CED2004, not more acceptable than, say, MBH1999 or MSH2005? Why shouldn’t one data set be more reminiscent of actual temperatures than any other? At, say, 1300AD the vertical spread of temperatures is approaching 1°C, which is greater than the instrumental increase over the past 150 years. And bear in mind that each worker’s curve is an average fit.

Various expert statisticians at the US National Academy of Sciences were scathing of Mann’s hockey stick study because he “used a type of principal component analysis that tends to bias the shape of the reconstructions” and because he downplayed the “uncertainties of the published reconstructions”. In other words, he fudged.

If you regard the composite blur shown in Figure 6.10(c) or the messy tangle of curves in Box 6.1, Figure 1, you could construe that temperature showed no fluctuation of note from 800AD to around 1900AD. But historical records attest to considerable centuries-long warmth during the Medieval Warm Period and chilliness during the Little Ice Age. You’d never guess it from the graphs though.

Sorry, but Gore and IPCC have not proved that anthropogenic GHG drive temperature and their climate projections are pure crystal-ball gazing.

Hi JohnH,

you finished your latest post with:
"Gore and IPCC have not proved that anthropogenic GHG drive temperature and their climate projections are pure crystal-ball gazing."

It's this kind of deliberate polemic that makes debate with denialists so difficult.

I go to great pains to qualify my statements when making climate change presentations, and I emphasise (as you do) that AGW is simply a theory. As any scientist knows, theories are never "proved", they are simply assessed against the evidence for closeness of fit, correlation with projections etc. "If I throw the ball up, it will come down" - and yes it does at exactly the predicted speed and momentum, suggesting Newton's theory of gravity warrants respect.

The hypothesis "Increases in atmospheric CO2 will lead to changes in climate" is subject to the same scientific principle. We apply our understanding of science to this hypothesis to generate projections of what these changes will be, and we test the evidence, modify the hypothesis, re-test, etc. And we submit this process to open scientific scrutiny, particularly peer assessment.

For you to suggest that such cautious, carefully-modelled projections based on AGW theory are "crystal-ball gazing" is insulting to *all* scientists, as it discredits the fundamental scientific approach of putting forward hypotheses and testing them against the evidence.

The case for AGW will never be "proven" (any more than you can "prove" the existence of gravity), but there is evidence to support it, and the precautionary principle must then apply given any cost-vs-risk analysis.

And even if AGW turns out to be wrong, why would anyone argue against reducing pollution, improving energy efficiency, and investing in clean, renewable energy sources so that we can preserve our irreplaceable fossil fuels for more valuable uses (such as medicines, plastics, fertilisers)?

John, you do yourself no credit by engaging in hyperbole and polemic. Perhaps you might re-read your own Clean Coal article and ask yourself what point were you trying to make? Was it to construct a soapbox, or was it to expose something important about the current approach to coal?