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Revisiting the Younger Dryas

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Guest Commentary by Chris Colose

One of the most intriguing and well-studied climatic events in the past is the Younger Dryas (YD), a rather abrupt climate change between ~12.9 and 11.6 thousand years ago. As the world was slowly warming and ice was retreating from the last glaciation, the YD effectively halted the transition to today’s relatively warm, interglacial conditions in many parts of the world. This event is associated with cold and dry conditions increasing with latitude in the North, temperature and precipitation influences on tropical and boreal wetlands, Siberian-like winters in much of the North Atlantic, weakening of monsoon intensity, and southward displacement of tropical rainfall patterns. RealClimate has previously discussed the YD (here and here) however there have been a number of developments in recent years which deserve further attention, particularly with respect to the spatial characteristics and causes of the YD.
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Information levels

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Rasmus’ recent post on the greenhouse effect raised some interesting points concerning the technical level at which posts or other public communications should be written. This was a relatively technical article as these things go, eschewing the very basic ‘the greenhouse effect is like a blanket’ but not really approaching the level of a technical paper on the subject (no line-by-line calculations for instance). Nonetheless, there were complaints that was too much to be absorbed by the lay public, counter-arguments that making it too simple was patronising, as well as complaints that the discussions were not technical enough (for instance in explaining stratospheric cooling). In these discussions there are clearly the outlines of a common debate, and perhaps a way forward in the future.

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The Muir Russell report

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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…

A simple recipe for GHE

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According to some recent reports (e.g. PlanetArk; The Guardian), the public concern about global warming may be declining. It’s not clear whether this is actually true: a poll conducted by researchers at Stanford suggests otherwise. In any case, the science behind climate change has not changed (also see America’s Climate Choices), but there certainly remains a problem in communicating the science to the public.

This makes me think that perhaps a new simple mental picture of the situation is needed. We can look at climate models, and they tell us what we can expect, but it is also useful to have an idea of why increased greenhouse gas concentrations result in higher surface temperatures. The saying “Everything should be made as simple as possible, but not simpler” has been attributed to Albert Einstein, which also makes me wonder if we – the scientists – need to reiterate the story of climate change in a different way.

Gavin has already discussed this (also see here and here), but it may be necessary to tell story over again, with a slightly different slant. So how can we explain how the greenhouse effect (GHE) work in both simple terms and with a new angle? I also want to explain why the middle atmosphere cools with increasing greenhouse gas concentrations associated with an increased GHE. Here I will try to present a conceptual and comprehensive picture of GHE, explaining both the warming in the lower part of the atmosphere as well as the cooling aloft, and where only the most central features are included. Also, it is important to provide a good background, and we need to start with some very fundamental facts.

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Penn State reports

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The last part of the Penn State inquiry has now reported unanimously that Mike Mann did not engage in any activity that violated scientific norms. Quoting from the report conclusions,

Conclusion of the Investigatory Committee as to whether research misconduct occurred:

The Investigatory Committee, after careful review of all available evidence, determined that there is no substance to the allegation against Dr. Michael E. Mann, Professor, Department of Meteorology, The Pennsylvania State University.

More specifically, the Investigatory Committee determined that Dr. Michael E. Mann did not engage in, nor did he participate in, directly or indirectly, any actions that seriously deviated from accepted practices within the academic community for proposing, conducting, or reporting research, or other scholarly activities.

The decision of the Investigatory Committee was unanimous.

What we said last time….

The uncertainty prayer

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Seen at a meeting yesterday:


Grant us…
The ability to reduce the uncertainties we can;
The willingness to work with the uncertainties we cannot;
And the scientific knowledge to know the difference.

(Drawn from a white paper on the use of climate models for water managers).

Discuss.

Leakegate: A retraction

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Back in February, we commented on the fact-free IPCC-related media frenzy in the UK which involved plentiful confusion, the making up of quotes and misrepresenting the facts. Well, a number of people have pursued the newspapers concerned and Simon Lewis at least filed a complaint (pdf) with the relevant press oversight body. In response, the Sunday Times (UK) has today retracted a story by Jonathan Leake on a supposed ‘Amazongate’ and published the following apology:

The article “UN climate panel shamed by bogus rainforest claim” (News, Jan 31) stated that the 2007 Intergovernmental Panel on Climate Change (IPCC) report had included an “unsubstantiated claim” that up to 40% of the Amazon rainforest could be sensitive to future changes in rainfall. The IPCC had referenced the claim to a report prepared for the World Wildlife Fund (WWF) by Andrew Rowell and Peter Moore, whom the article described as “green campaigners” with “little scientific expertise.” The article also stated that the authors’ research had been based on a scientific paper that dealt with the impact of human activity rather than climate change.

In fact, the IPCC’s Amazon statement is supported by peer-reviewed scientific evidence. In the case of the WWF report, the figure had, in error, not been referenced, but was based on research by the respected Amazon Environmental Research Institute (IPAM) which did relate to the impact of climate change. We also understand and accept that Mr Rowell is an experienced environmental journalist and that Dr Moore is an expert in forest management, and apologise for any suggestion to the contrary.

The article also quoted criticism of the IPCC’s use of the WWF report by Dr Simon Lewis, a Royal Society research fellow at the University of Leeds and leading specialist in tropical forest ecology. We accept that, in his quoted remarks, Dr Lewis was making the general point that both the IPCC and WWF should have cited the appropriate peer-reviewed scientific research literature. As he made clear to us at the time, including by sending us some of the research literature, Dr Lewis does not dispute the scientific basis for both the IPCC and the WWF reports’ statements on the potential vulnerability of the Amazon rainforest to droughts caused by climate change.

In addition, the article stated that Dr Lewis’ concern at the IPCC’s use of reports by environmental campaign groups related to the prospect of those reports being biased in their conclusions. We accept that Dr Lewis holds no such view – rather, he was concerned that the use of non-peer-reviewed sources risks creating the perception of bias and unnecessary controversy, which is unhelpful in advancing the public’s understanding of the science of climate change. A version of our article that had been checked with Dr Lewis underwent significant late editing and so did not give a fair or accurate account of his views on these points. We apologise for this.

Note that the Sunday Times has removed the original article from their website (though a copy is available here), and the retraction does not appear to have ever been posted online. Here is a scan of the print version just in case there is any doubt about its existence. (Update: the retraction has now appeared).

This follows on the heels of a German paper, the Frankfurter Rundschau, recently retracting a story on the ‘Africagate’ non-scandal, based on reporting from….. Jonathan Leake.

It is an open question as to what impact these retractions and apologies have, but just as with technical comments on nonsense articles appearing a year after the damage was done, setting the record straight is a important for those people who will be looking at this at a later date, and gives some hope that the media can be held (a little) accountable for what they publish.

Five Thousand Gulf Oil Spills

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That’s the rate that people are releasing carbon to the atmosphere from fossil fuel combustion and deforestation today. I know, it’s apples and oranges; carbon in the form of oil is more immediately toxic to the environment than it is as CO2 (although CO2 may be more damaging on geologic time scales). But think of it — five thousand spills like in the Gulf of Mexico, all going at once, each releasing 40,000 barrels a day, every day for decades and centuries on end. We are burning a lot of carbon!

Atlantic Tropical Cyclone Records – Trends and Ephemerality

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Guest Commentary from Urs Neu

To understand the influence of climate change on tropical cyclone and hurricane activity, it is crucial to know how this activity has varied in the past. There have been a number of interesting new studies of Atlantic tropical cyclones (TCs) and hurricanes (tropical cyclones with maximum sustained winds exceeding 74 miles per hour) since my review of the topic a couple years ago (see here and here). These newer studies underscore that, while our knowledge continues to improve in this area, key uncertainties persist. In particular, it remains very difficult to confidently estimate trends in the past.

In assessing past trends, one must distinguish between two distinct time intervals: 1) the period of historical observations (mainly after 1850), and 2) the earlier period for which TC activity can only be reconstructed using proxy data. Furthermore, we have to distinguish between trends in tropical cyclone (TC) number and TC intensity–the latter measure is particularly important from the standpoint of impacts. There is no a priori reason to expect these quantities to vary in concert, either in the past, or in the future. Unfortunately, uncertainties are much greater for intensity than for counts.

In this article, I will review our current understanding of Atlantic TC and hurricane trends with respect to: A) the historical record of basin-wide TC numbers; B) the historical record of hurricanes and TC intensity; C) distant past proxy estimates of TC (primarily, hurricane only) counts; and D) distant past proxy measures of TC/hurricane intensity. I will conclude with a discussion of current methods for forecasting Atlantic hurricane activity.

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