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Curve-fitting and natural cycles: The best part

It is not every day that I come across a scientific publication that so totally goes against my perception of what science is all about. Humlum et al., 2011 present a study in the journal Global and Planetary Change, claiming that most of the temperature changes that we have seen so far are due to natural cycles.

They claim to present a new technique to identify the character of natural climate variations, and from this, to produce a testable forecast of future climate. They project that

the observed late 20th century warming in Svalbard is not going to continue for the next 20–25 years. Instead the period of warming may be followed by variable, but generally not higher temperatures for at least the next 20–25 years.

However, their claims of novelty are overblown, and their projection is demonstrably unsound.

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  1. O. Humlum, J. Solheim, and K. Stordahl, "Identifying natural contributions to late Holocene climate change", Global and Planetary Change, vol. 79, pp. 145-156, 2011.

Two-year old turkey

Filed under: — gavin @ 22 November 2011

The blogosphere is abuzz with the appearance of a second tranche of the emails stolen from CRU just before thanksgiving in 2009. Our original commentary is still available of course (CRU Hack, CRU Hack: Context, etc.), and very little appears to be new in this batch. Indeed, even the out-of-context quotes aren’t that exciting, and are even less so in-context.

A couple of differences in this go around are worth noting: the hacker was much more careful to cover their tracks in the zip file they produced – all the file dates are artificially set to Jan 1 2011 for instance, and they didn’t bother to hack into the RealClimate server this time either. Hopefully they have left some trails that the police can trace a little more successfully than they’ve been able to thus far from the previous release.

But the timing of this release is strange. Presumably it is related to the upcoming Durban talks, but it really doesn’t look like there is anything worth derailing there at all. Indeed, this might even increase interest! A second release would have been far more effective a few weeks after the first – before the inquiries and while people still had genuine questions. Now, it just seems a little forced, and perhaps a symptom of the hacker’s frustration that nothing much has come of it all and that the media and conversation has moved on.

If anyone has any questions about anything they see that seems interesting, let us know in the comments and we’ll see if we can provide some context. We anticipate normal service will be resumed shortly.

Review of Spencer’s ‘Great Global Warming Blunder’

Filed under: — group @ 28 April 2011

Guest commentary from Steve Ghan

A good writer knows their audience, and Roy Spencer knows his. There are plenty of people who would love to hear a compelling argument for why no action is needed to mitigate global warming, and Spencer’s book “The Great Global Warming Blunder: How Mother Nature Fooled the World’s Top Climate Scientists” will give uncritical readers the argument they’ve been looking for. As Sarah Palin said, “while we recognize the occurrence of these natural, cyclical environmental trends, we can’t say with assurance that man’s activities cause weather change”. That is really the essence of Roy’s argument.
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The Starship vs. Spaceship Earth

Eric Steig & Ray Pierrehumbert

One of my (Eric’s) favorite old books is The Starship and the Canoe by Kenneth Brower It’s a 1970s book about a father (Freeman Dyson, theoretical physicist living in Princeton) and son (George Dyson, hippy kayaker living 90 ft up in a fir tree in British Columbia) that couldn’t be more different, yet are strikingly similar in their originality and brilliance. I started out my career heading into astrophysics, and I’m also an avid sea kayaker and I grew up with the B.C. rainforest out my back door. So I think I have a sense of what drives these guys. Yet I’ve never understood how Freeman Dyson became such a climate contrarian and advocate for off-the-wall biogeoengineering solutions like carbon-eating trees, something we’ve written about before.

It turns out that Brower has wondered the same thing, and in a recent article in The Atlantic, he speculates on the answer. “How could someone as smart as Freeman Dyson,” writes Brower, “be so wrong about climate change and other environmental concerns..?”
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West Antarctica: still warming

The temperature reconstruction of O’Donnell et al. (2010) confirms that West Antarctica is warming — but underestimates the rate

Eric Steig

At the end of my post last month on the history of Antarctic science I noted that I had an initial, generally favorable opinion of the paper by O’Donnell et al. in the Journal of Climate. O’Donnell et al. is the peer-reviewed outcome of a series of blog posts started two years ago, mostly aimed at criticizing the 2009 paper in Nature, of which I was the lead author. As one would expect of a peer-reviewed paper, those obviously unsupportable claims found in the original blog posts are absent, and in my view O’Donnell et al. is a perfectly acceptable addition to the literature. O’Donnell et al. suggest several improvements to the methodology we used, most of which I agree with in principle. Unfortunately, their actual implementation by O’Donnell et al. leaves something to be desired, and yield a result that is in disagreement with independent evidence for the magnitude of warming, at least in West Antarctica.

In this post, I’ll summarize the key methodological changes suggested by O’Donnell et al., discuss how their results compare with our results, and the implications for our understanding of recent Antarctic climate change. I’ll then try to make sense of how O’Donnell et al. have apparently wound up with an erroneous result.
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