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about Gavin Schmidt

Gavin Schmidt is a climate modeler, working for NASA and with Columbia University.

Why bother trying to attribute extreme events?

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Nature has an interesting editorial this week on the state of the science for attributing extreme events. This was prompted by a workshop in Oxford last week where, presumably, strategies, observations and results were discussed by a collection of scientists interested in the topic (including Myles Allen, Peter Stott and other familiar names). Rather less usual was a discussion, referred to in the Nature piece, on whether the whole endeavour was scientifically worthwhile, and even if it was, whether it was of any use to anyone. The proponents of the ‘unscientific and pointless’ school of thought were not named and so one can’t immediately engage with them directly, but nonetheless the question is worthy of a discussion.

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Extreme metrics

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There has been a lot of discussion related to the Hansen et al (2012, PNAS) paper and the accompanying op-ed in the Washington Post last week. But in this post, I’ll try and make the case that most of the discussion has not related to the actual analysis described in the paper, but rather to proxy arguments for what people think is ‘important’.
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References

  1. J. Hansen, M. Sato, and R. Ruedy, "Perception of climate change", Proceedings of the National Academy of Sciences, vol. 109, 2012. http://dx.doi.org/10.1073/pnas.1205276109

Arctic sea ice minimum 2012…

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By popular demand, a thread devoted to the continuing decline of Arctic sea ice, and a potential new record minimum this year. As before, the figures are hot-linked and will update day-by-day.

JAXA Sea ice extent:



Cryosphere Today sea ice concentration (interactive chart):



Estimated sea ice volume from UW PIOMAS (updated every month):



Other links: Tamino, the very informative and detailed Neven’s sea ice blog , and some interesting predictions from Gareth Renowden.

Let the games begin!

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I picked a good weekend to be out of cell phone range and unconnected to the internet – and judging from how the rest of the week has gone, I’d have been minded to stay there…

As most readers are probably aware, there was an op-ed in the Saturday New York Times from Richard Muller announcing the Berkeley Earth team’s latest results. It was odd enough that a scientific paper was announced via an op-ed, rather than a press release, odder still that the paper was only being submitted and had not actually been accepted, and most odd of all was the framing – a ‘converted skeptic’ being convinced by his studies that the planet has indeed warmed and that human activity is the cause – which as Mike and Ken Caldiera pointed out has been known for almost 2 decades.

Not wanting to be upstaged, plenty of ‘unconverted skeptics’ – including Anthony Watts and Ross McKitrick decided to stage dramatic press events and release barbs of their own. This was followed by a general piling on of commenters and bloggers trying to spin the events in their preferred direction combined with plenty of cluelessness in the general media about exactly who these people are (no-one special), what earth-shattering discovery had been made (none) and what it all means (not a lot).

The ‘best’ response to this circus is to sit back and see how pretzel-like the logical justifications can become. I particularly like the recent twist to the “No true scotsman” post-hoc rationalisation. Since the ‘converted skeptic’/prodigal scientist meme is a very powerful framing for the media, the obvious riposte for the ‘skeptics’ is to declare that Muller was not a true skeptic. But since these terms have become meaningless in terms of any specific position, this ends up as a semantic argument that convinces no-one but the faithful.

The actual trigger for all this hoopla is the deadline for papers that can be cited in the Second Order Draft of the new IPCC report. They needed to have been submitted to a journal by Tuesday (31 July) to qualify. Of course, they also need to be interesting, relevant and known to the IPCC lead authors. But there seems to be far too much emphasis being put on this deadline. The AR5 report is pretty much 90% written, and the broad outlines have been known for ages. Very few of the papers that have been submitted this week are anything other than minor steps forward and only a small number will be accorded anything other than a brief mention in AR5, and most not even that.

Furthermore, once the SOD is finalised (Aug 10), Tuesday’s deadline becomes moot, and the only thing that matters for the final report is whether papers are accepted by March 2013. (In a spirit of full disclosure, I should mention that I was working on a couple of papers with an eye to making this deadline, but in the end decided it was preferable to take the time to do a good job on the papers than to submit something shoddy).

The only worthwhile substance to any of this is the work that has mostly been done by Robert Rohde on the Berkeley Earth code and database as we’ve noted previously – and once this week’s drama has faded into the distance overshadowed by some new blog-storm, this work will still be a useful advance.

But still the games go on. Senate hearings are one of the longest running games of political theatre going – where the Senators pretend to listen to the panelists and the panelists pretend that this is an efficient way to inform policymakers. This week’s was little different from the ones in the past – some earnest submissions from the mainstream, and a cherry-pickers delight of misinformation from the Republican invitee, John Christy, who even quoted the woefully inept first draft of the Watts paper as if it meant something.

To confuse the metaphor even further, Roger Pielke Sr loudly declared that whatever the results of the Watts paper it will end up being a game changer:

The TOB effect could result in a confirmation of the Watts et al conclusion, or a confirmation (from a skeptical source) that siting quality does not matter. In either case, this is still a game changing study.

If only people would change the games they play…

My inclination is just to sit back and watch the spectacle, admire the logic-defying leaps, marvel at the super-human feats of hubris and, in two weeks time, remark on how little actually changed.

OHC Model/Obs Comparison Errata

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This is just a brief note to point out that a few graphs that I have put together showing Ocean Heat Content changes in recent decades had an incorrect scaling for the GISS model data. My error was in assuming that the model output (which were in units W yr/m2) were scaled for the ocean area only, when in fact they were scaled for the entire global surface area (see fig. 2 in Hansen et al, 2005). Therefore, in converting to units of 1022 Joules for the absolute ocean heat content change, I had used a factor of 1.1 (0.7 x 5.1 x 365 x 3600 x 24 x 10-8), instead of the correct value of 1.61 (5.1 x 365 x 3600 x 24 x 10-8). This problem came to light while we were redoing this analysis for the CMIP5 models and from conversations with dana1981 at skepticalscience.com.

These graphs appeared in Dec 2009, May 2010, Jan 2011 and Feb 2012. In each case, I have replaced the graph with a corrected version while leaving a link to the incorrect version. Links to the figures will return the corrected image (and this is noted on the image itself). Where possible I used the data that were current at the time of the original post. Fortunately this only affects the figures used in these blog postings and not in any publications. Apologies for any confusion.

This figure shows the comparison using the most up-to-date observational products (NODC, PMEL):

The basic picture is unchanged – model simulations were able to capture the historical variance in OHC (as best we know it now – there remains significant structural uncertainty in those estimates). There are clear dips related volcanic eruptions (Agung, El Chichon, Pinatubo), and an sharp increase in the 1990s. Note that in GISS-EH (same AGCM but with a different ocean model) OHC increases at a slightly slower rate than seen with GISS-ER above. Looking at the last decade, it is clear that the observed rate of change of upper ocean heat content is a little slower than previously (and below linear extrapolations of the pre-2003 model output), and it remains unclear to what extent that is related to a reduction in net radiative forcing growth (due to the solar cycle, or perhaps larger than expected aerosol forcing growth), or internal variability, model errors, or data processing – arguments have been made for all four, singly and together.

Analyses of the CMIP5 models will provide some insight here since the historical simulations have been extended to 2012 (including the last solar minimum), and have updated aerosol emissions. Watch this space.

References

  1. J. Hansen, L. Nazarenko, R. Ruedy, M. Sato, J. Willis, A. Del Genio, D. Koch, A. Lacis, K. Lo, S. Menon, T. Novakov, J. Perlwitz, G. Russell, G.A. Schmidt, and N. Tausnev, "Earth's Energy Imbalance: Confirmation and Implications", Science, vol. 308, pp. 1431-1435, 2005. http://dx.doi.org/10.1126/science.1110252

Yamalian yawns

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Steve McIntyre is free to do any analysis he wants on any data he can find. But when he ladles his work with unjustified and false accusations of misconduct and deception, he demeans both himself and his contributions. The idea that scientists should be bullied into doing analyses McIntyre wants and delivering the results to him prior to publication out of fear of very public attacks on their integrity is ludicrous.

By rights we should be outraged and appalled that (yet again) unfounded claims of scientific misconduct and dishonesty are buzzing around the blogosphere, once again initiated by Steve McIntyre, and unfailingly and uncritically promoted by the usual supporters. However this has become such a common occurrence that we are no longer shocked nor surprised that misinformation based on nothing but prior assumptions gains an easy toehold on the contrarian blogs (especially at times when they are keen to ‘move on’ from more discomforting events).

So instead of outrage, we’ll settle for simply making a few observations that undermine the narrative that McIntyre and company are trying to put out.
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Updating the CRU and HadCRUT temperature data

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The latest incarnation of the CRUTEM land surface temperatures and the HadCRUT global temperatures are out this week. This is the 4th version of these products, which have undergone a number of significant changes over that time and so this is a good opportunity to discuss how and why data products evolve and what that means in the bigger scheme of things.

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Misrepresentation from Lindzen

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Richard Lindzen is a very special character in the climate debate – very smart, high profile, and with a solid background in atmospheric dynamics. He has, in times past, raised interesting critiques of the mainstream science. None of them, however, have stood the test of time – but exploring the issues was useful. More recently though, and especially in his more public outings, he spends most of his time misrepresenting the science and is a master at leading people to believe things that are not true without him ever saying them explicitly.

However, in his latest excursion at a briefing at the House of Lords Commons in the UK, among the standard Lindzen arguments was the following slide (which appears to be a new addition):

What Lindzen is purporting to do is to compare the NASA GISS temperature product from 2012 to the version in 2008 (i.e. the y-axis is the supposedly the difference between what GISS estimated the anomaly to be in 2012 relative to 2008). A rising trend would imply that temperatures in more recent years had been preferentially enhanced in the 2012 product. The claim being made is that NASA GISS has ‘manipulated’ (in a bad way) the data in order to produce an increasing trend of global mean temperature anomalies (to the tune of 0.14ºC/Century compared to the overall trend of 0.8ºC/Century) between the 2008 and 2012 versions of the data, which are apparently shown subtracted from each other in Lindzen’s figure. Apparently, this got ‘a big laugh’ at his presentation.

However, this is not in the least bit true: the data are not what he claims, the interpretation is wrong, and the insinuations are spurious.

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2011 Updates to model-data comparisons

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And so it goes – another year, another annual data point. As has become a habit (2009, 2010), here is a brief overview and update of some of the most relevant model/data comparisons. We include the standard comparisons of surface temperatures, sea ice and ocean heat content to the AR4 and 1988 Hansen et al simulations.
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