Readers may recall discussions of a paper by Thompson et al (2008) back in May 2008. This paper demonstrated that there was very likely an artifact in the sea surface temperature (SST) collation by the Hadley Centre (HadSST2) around the end of the second world war and for a few years subsequently, related to the different ways ocean temperatures were taken by different fleets. At the time, we reported that this would certainly be taken into account in revisions of data set as more data was processed and better classifications of the various observational biases occurred. Well, that process has finally resulted in the publication of a new compilation, HadSST3.
[Read more…] about Revisiting historical ocean surface temperatures
Instrumental Record
Rescuing data…
Guest commentary by Vicky Slonosky
One of the lesser-known branches of climatology is historical climatology, the study of past climates from historical records of instrumental observations and weather descriptions, with “historical” often loosely taken to mean “pre-government-organized-meteorological or weather service” observations. In the last ten years or so, with the development of digital imaging, increased storage and processing capabilities of computers, it’s become possible to think about analyzing these past records on a daily basis. Snowstorms, hurricanes, cold snaps or heat waves all happen on daily scales, and daily information over the past 200 years or more let us learn more about them. All over the world, efforts (many unfunded) are going on to try to find and preserve these historical data from personal weather diaries, scientific observatories and naval records. This is often described as “data archeology and rescue”, which has a nice ring to it, and even manages to make going through dusty boxes in dustier basements and typing in the original (often handwritten) observations sound glamorous and exciting. It’s not a simple task though:
“All my attention for recent years has been directed to that branch of meteorology connected with ascertaining the mean temperature of Lower Canada. I had not made up my mind as to the fact of the climate having materially altered but was impressed generally with the belief that the climate had improved, or become warmer, as it had increased in population and cultivation … I resolved to make diligent search for such records as might be found in the Province, in order to answer this interesting question. The difficulty of this experience was even greater than I had anticipated. Few individuals had turned their attention to this (even now) infant science, at a period sufficiently removed to bear comparison with the present, and of those which I was fortunate enough to discover, many were unsuitable from the irregular manner in which they were kept … None but the most zealous meteorologist knows how very difficult it is to obtain observations in this science which can be depended upon.”
John Samuel McCord, acc. 0882, McCord Museum of Canadian History Archives, circa 1838.
How easy it is to get fooled
When you analyse your data, you usually assume that you know what the data really represent. Or do you? This has been a question that over time has marred studies on solar activity and climate, and more recently cosmic rays and clouds. And yet again, this issue pops up in two recent papers; One by Feulner (‘The Smithsonian solar constant data revisited‘) and another by Legras et al. (‘A critical look at solar-climate relationships from long temperature series.’). Both these papers show how easily it is to be fooled by your data if you don’t know what they really represent.
Going to extremes
There are two new papers in Nature this week that go right to the heart of the conversation about extreme events and their potential relationship to climate change. This is a complex issue, and one not well-suited to soundbite quotes and headlines, and so we’ll try and give a flavour of what the issues are and what new directions these new papers are pointing towards.
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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.
[Read more…] about West Antarctica: still warming
2010 updates to model-data comparisons
As we did roughly a year ago (and as we will probably do every year around this time), we can add another data point to a set of reasonably standard model-data comparisons that have proven interesting over the years.
[Read more…] about 2010 updates to model-data comparisons
The A-train
A little behind schedule, I finally found time to read the article in the July 2010 edition of Physics Today “Touring the atmosphere aboard the A-Train” by Tristan S. L’Ecuyer and Jonathan H. Jiang. I think this article is a worth-while read, telling a fascinating story about how new satellite missions lead to greater understanding of our climate system.
Doing it yourselves
We’ve been a little preoccupied recently, but there are some recent developments in the field of do-it-yourself climate science that are worth noting.
[Read more…] about Doing it yourselves
Happy 35th birthday, global warming!
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) Global warming is turning 35! Not only has the current spate of global warming been going on for about 35 years now, but also the term “global warming” will have its 35th anniversary next week. On 8 August 1975, Wally Broecker published his paper “Are we on the brink of a pronounced global warming?” in the journal Science. That appears to be the first use of the term “global warming” in the scientific literature (at least it’s the first of over 10,000 papers for this search term according to the ISI database of journal articles).
In this paper, Broecker correctly predicted “that the present cooling trend will, within a decade or so, give way to a pronounced warming induced by carbon dioxide”, and that “by early in the next century [carbon dioxide] will have driven the mean planetary temperature beyond the limits experienced during the last 1000 years”. He predicted an overall 20th Century global warming of 0.8ºC due to CO2 and worried about the consequences for agriculture and sea level.
The Muir Russell report
by Gavin and Mike
The long-awaited and surprisingly thorough Muir Russell report (readable online version) was released this morning. We’ve had a brief read through of the report, but a thorough analysis of this and the supplemental information on the web site will have to wait for a day or so.
The main issue is that they conclude that the rigour and honesty of the CRU scientists is not in doubt. For anyone who knows Phil Jones and his colleagues this comes as no surprise, and we are very pleased to have this proclaimed so vigorously. Secondly, they conclude that none of the emails cast doubt on the integrity and conclusions of the IPCC, again, something we have been saying since the beginning. They also conclude as we did that there was no ‘corruption’ of the peer-review process. Interestingly, they independently analysed the public domain temperature data themselves to ascertain whether the could validate the CRU record. They managed this in two days, somewhat undermining claims that the CRU temperature data was somehow manipulated inappropriately. (Note that this exercise has been undertaken by a number of people since November – all of which show that the CRU results are robust).
All in all, none of the various accusations and insinuations that have been floating around the blogosphere have been sustained. (See some of the early media coverage of the report).
However, there are two issues that have come up that deserve some comment. The first are the evolving practices of data presentation and access, and the second is the issue of how to handle Freedom of Information (FOI) requests.
As climate science has moved away from single researcher/single study/single site analyses towards synthesis across multiple studies, across the globe and involving more and more researchers, practices that were appropriate at one time don’t necessarily scale up to the new environment. Data requests dealt with on an ad-hoc and informal basis work fine if only a couple of people are interested, but more formal and automated procedures are needed when the data sets grow and many more people are involved (see the PCMDI/CMIP3 archive of model results for instance). Given too, the obsession in certain quarters with irrelevant details of smoothing techniques and end-point padding in decade-old papers, it is clear that the more information that is put out as supplementary material to the creation of high-profile figures, the better off we will be. Examples of this for figures in IPCC AR4 already exist, but it will be helpful for IPCC to adopt this practice more generally. Historically, this hasn’t been done – mainly because no-one thought it particularly interesting (most smoothing methods produce very similar results for instance), particularly for figures that weren’t for publication in the technical literature.
One example of this was the cover art on a WMO 1999 report which, until last November, was completely obscure (we are not aware of any mention of this report or this figure before November in any blogospheric discussion, ever). Nonetheless, in the way of these things, this figure is now described as ‘an icon’ in the Muir Russell report (one of their very few mistakes, how can something be an icon if no-one has ever seen it?). In retrospect (and as we stated last year) we agree with the Muir Russell report that the caption and description of the figure could indeed have been clearer, particularly with regard to the way proxy and instrumental data sources were spliced into a single curve, without indicating which was which. The WMO cover figure appears (at least to our knowledge) to be the only instance where that was done. Moving forward, nonetheless, it is advisable that scientists be as clear as possible about what sorts of procedures have gone into the preparation of a figure. But retrospective applications of evolving standards are neither fair nor useful.
With respect to the continuing barrage of FOI requests (which are predominantly for personal communications rather than for data), we can attest from personal experience how disconcerting these can be at first. Since there are no limits on what can be asked for (though there are many limits on what will be delivered), scientists presented with these requests often find them personally invasive and inappropriate. Institutions that do not have much experience with these kinds of requests, and who are not aware of what their employees do that is, and is not, covered by the legislation, are often not much help in sorting out how to respond. This can certainly be improved, as can the awareness of the community of what is recoverable using these procedures. While it is not relevant to the legislation, nor to what can be released, the obvious bad faith of many of the requesters indicates that actual information about the functioning of public bodies is not the primary goal in making these requests. However, it would be a terrible mistake for scientists to retreat from the public discussion on climate science because of these attempts at intimidation.
We will post on more specific aspects of the report, and perhaps the legacy of the whole affair over the next few days…