Re: More proof that global warming is a hoax ...

Dr. Dweeb wrote:

....

I have a suspicion that several contributors to this thread, should they be capable of reading and understanding this article, may enter into one of two states - denial or cognitive dissonance.

Dweeb
http://www.iarc.uaf.edu/highlights/2007/akasofu_3_07/Earth_recovering_from_LIA.pdf

Hmmm - since you offered up this paper apparently in defense of your own position, perhaps you yourself weren't capable of reading and understanding it.

But I'll give you a hand:

It gets off to a good start by observing that "there is a possibility that only a fraction of the present warming trend may be attributed to the greenhouse effect resulting from human activities" - thus clearly agreeing that at least *some* of the observed warming *is* attributable to "the greenhouse effect resulting from human activities." It quickly follows with "it is well known that CO2 causes the greenhouse effect; therefore, it is natural to hypothesize that CO2 is a cause of the present warming trend" just in case you were in any doubt about its acceptance of this thesis.

Perhaps you drew encouragement from its timid declaration that "there is so far no definitive proof that “most” of the present warming is due to the greenhouse effect, as is stated in the recently published IPCC Report (2007)." As I've observed elsewhere, asking for 'definitive proof' of this kind of projection is asking for stone tablets from God - otherwise, all we'll get are the best projections that science can offer. And if the IPCC report actually suggested that such 'definitive proof' existed (a 'fact' not actually in evidence, of course), then that part of it was hogwash.

Unlike the propaganda film that you enjoyed so much, this paper does not attempt to use the modest temperature decline from 1940 - 1975 to debunk the idea of CO2-related global warming, but merely (and rightly) to observe that temperature variations depend on more complex variables than CO2 alone.

The first questionable (and apparently unsupported) assertion in the paper is that "it is unlikely that CO2 caused any major temperature fluctuations before 1940" - despite the fact that we've been burning coal since the Bronze age and very actively indeed since the industrial revolution began in the 1700s. While the *rate* of fossil fuel CO2 emission has increased dramatically since around 1940, completely ignoring the cumulative effects of a couple of centuries of earlier significant use (though at noticeably lower rates) seems a bit cavalier when attempting to determine a 'natural' baseline temperature curve from which to infer how much additional effect our own CO2 emissions have had - and his own graph indicates that indeed atmospheric concentration of CO2 was increasing, albeit at a slower rate, well before 1940.

Unfortunately, the author's *entire thesis* rests on this assumption - that the roughly linear temperature rise measured since 1800 has been due not primarily to human CO2 emissions (though they were already going great guns by then, and kept doing so until their even more dramatic rise starting around 1940) but to other causes, with human contributions a relatively minor addition.

He then returns to better science, however, by noting that the absence of a clearly-identifiable jump in temperatures *after* 1940 is likely due to the superposition of shorter-term fluctuations (again departing materially from what the propaganda film would have one believe). He also rightly observes that there's no particular reason to suspect that the 'Little Ice Age' ended around 1900 (or even has ended now) - so positing (as he does at the end) that we're simply rebounding from it as the result of some natural process is a bit presumptuous (given that there's no particular reason to think any such rebound has even started yet). And he mentions that other interglacial periods were warmer than this one but (again, quite rightly) does not attempt to draw any conclusions about the effect of man-made CO2 emissions from this (though that does raise the question of why he mentioned this at all).

Unfortunately, he is less perceptive in discussing sea-level changes: he observes that no post-1940 effects are evident without recognizing that the short-term temperature drop more than adequately accounts for this supposed discrepancy; of course, the fact that sea level has been rising consistently with temperature increases over the past century is still worth noting (for those who cheerfully look forward to a balmier future without adverse side-effects, as some in the propaganda film did).

His description of 'hind-casting' difficulties near the end is interesting, but says more about the need to continue working on better modeling than anything else.

In any event, the bottom line is that the author attempts to assign only some unspecified percentage of *observable* global temperature rise to man-made causes (such as *observable* increases in atmospheric CO2 concentration which in fact correlate quite well both with that temperature rise and with the amount of CO2 that we know we are releasing - once again, in marked contrast to the propaganda film's suggestion that higher CO2 levels are the *result* of rising temperatures and have nothing to do with our activity) while explaining away the rest by hypothesizing the existence of some 'natural increase' from unspecified (and thus unobservable) causes. It does make an interesting (if somewhat fuzzily-thought-out) hypothesis, but that's about it - though I won't disparage him too much, since he clearly does subscribe to the theory that there's *some* contribution from man-made CO2 emissions and merely questions what the absolute amount is.

- bill
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