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Instrumental Record

Muddying the peer-reviewed literature

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We’ve often discussed the how’s and why’s of correcting incorrect information that is occasionally found in the peer-reviewed literature. There are multiple recent instances of heavily-promoted papers that contained fundamental flaws that were addressed both on blogs and in submitted comments or follow-up papers (e.g. McLean et al, Douglass et al., Schwartz). Each of those wasted a huge amount of everyone’s time, though there is usually some (small) payoff in terms of a clearer statement of the problems and lessons for subsequent work. However, in each of those cases, the papers were already “in press” by the time other people were aware of the problems.

What is the situation though when problems (of whatever seriousness) are pointed out at an earlier stage? For instance, when a paper has been accepted in principle but a final version has not been sent in and well before the proofs have been sent out? At that point it would seem to be incumbent on the authors to ensure that any errors are fixed before they have a chance to confuse or mislead a wider readership. Often in earlier times corrections and adjustments would have been made using the ‘Note added in proof’, but this is less used these days since it is so easy to fix electronic versions.
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A warming pause?

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The blogosphere (and not only that) has been full of the “global warming is taking a break” meme lately. Although we have discussed this topic repeatedly, it is perhaps worthwhile reiterating two key points about the alleged pause here.

(1) This discussion focuses on just a short time period – starting 1998 or later – covering at most 11 years. Even under conditions of anthropogenic global warming (which would contribute a temperature rise of about 0.2 ºC over this period) a flat period or even cooling trend over such a short time span is nothing special and has happened repeatedly before (see 1987-1996). That simply is due to the fact that short-term natural variability has a similar magnitude (i.e. ~0.2 ºC) and can thus compensate for the anthropogenic effects. Of course, the warming trend keeps going up whilst natural variability just oscillates irregularly up and down, so over longer periods the warming trend wins and natural variability cancels out.

(2) It is highly questionable whether this “pause” is even real. It does show up to some extent (no cooling, but reduced 10-year warming trend) in the Hadley Center data, but it does not show in the GISS data, see Figure 1. There, the past ten 10-year trends (i.e. 1990-1999, 1991-2000 and so on) have all been between 0.17 and 0.34 ºC per decade, close to or above the expected anthropogenic trend, with the most recent one (1999-2008) equal to 0.19 ºC per decade – just as predicted by IPCC as response to anthropogenic forcing.

GISS temperature trends

Figure 1. Global temperature according to NASA GISS data since 1980. The red line shows annual data, the larger red square a preliminary value for 2009, based on January-August. The green line shows the 25-year linear trend (0.19 ºC per decade). The blue lines show the two most recent ten-year trends (0.18 ºC per decade for 1998-2007, 0.19 ºC per decade for 1999-2008) and illustrate that these recent decadal trends are entirely consistent with the long-term trend and IPCC predictions. Even the highly “cherry-picked” 11-year period starting with the warm 1998 and ending with the cold 2008 still shows a warming trend of 0.11 ºC per decade (which may surprise some lay people who tend to connect the end points, rather than include all ten data points into a proper trend calculation).

Una traducción en español está disponible aquí.
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Winds of change

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Gavin Schmidt and Michael Mann

There was an interesting AP story this week about possible changes in wind speed over the continental US. The study (by Pryor et al (sub.)), put together a lot of observational data, reanalyses (from the weather forecasting models) and regional models, and concluded that there was some evidence for a decrease in wind speeds, particularly in the Eastern US. However, although this trend appeared in the observational data, it isn’t seen in all the reanalyses or regional models, leaving open a possibility that the trend is an artifact of some sort (instrumental changes, urbanization etc.). If the effect is real though, one would want to see whether it could be tied to anything else (such as forcing from greenhouse gas or aerosol increases), and indeed, whether it had any implications for wind-generated electricity, water evaporation etc.

Amusingly, both of us were quoted in the story as having ostensibly conflicting views. Mike was quoted as finding the evidence for a trend reasonably convincing, while Gavin was quoted as being unconvinced of the evidence for an anthropogenic climate change signal (note that the two statements are not in fact mutually inconsistent). As one should expect in any news story, these single lines don’t really do justice to the longlonger interviews both of us gave the reporter Seth Borenstein. So what is the bigger context?
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On overfitting

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I don’t tend to read other blogs much, despite contributing to RealClimate. And I’m especially uninterested in spending time reading blogs full of ad hominem attacks. But a handful of colleagues apparently do read this stuff, and have encouraged me to take a look at the latest commentaries on our Antarctic temperature story. Since I happen to be teaching about principal component analysis to my graduate students this week, I thought it would be worthwhile to put up a pedagogical post on the subject. (If you don’t know what principal component analysis (PCA) is, take a look at our earlier post, Dummy’s Guide to the Hockey Stick Controversy).
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ACRIM vs PMOD

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Two recent papers (Lockwood & Fröhlich, 2008 – ‘LF08’; Scafetta & Willson, 2009 – ‘SW09’) compare the analysis of total solar irradiance (TSI) and the way the TSI measurements are combined to form a long series consisting of data from several satellite missions. The two papers come to completely opposite conclusions regarding the long term trend. So which one (if either) is right, then? And does it really matter?

Una traduzione in italiano è disponibile qui
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Monckton’s deliberate manipulation

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Our favorite contrarian, the potty peer Christopher Monckton has been indulging in a little aristocratic artifice again. Not one to be constrained by mere facts or observable reality, he has launched a sally against Andy Revkin for reporting the shocking news that past industry disinformation campaigns were not sincere explorations of the true uncertainties in climate science.
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Yet more aerosols: Comment on Shindell and Faluvegi

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Guest post from Drew Shindell, NASA GISS

Our recent paper “Climate response to regional radiative forcing during the twentieth century”, has generated some interesting discussion (some of it very ‘interesting’ indeed). So this post is an attempt to give a better context to the methods and implications of the study.

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Michaels’ new graph

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Every so often people who are determined to prove a particular point will come up with a new way to demonstrate it. This new methodology can initially seem compelling, but if the conclusion is at odds with other more standard ways of looking at the same question, further investigation can often reveal some hidden dependencies or non-robustness. And so it is with the new graph being cited purporting to show that the models are an “abject” failure.

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Antarctic warming is robust

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The difference between a single calculation and a solid paper in the technical literature is vast. A good paper examines a question from multiple angles and find ways to assess the robustness of its conclusions to all sorts of possible sources of error — in input data, in assumptions, and even occasionally in programming. If a conclusion is robust over as much of this as can be tested (and the good peer reviewers generally insist that this be shown), then the paper is likely to last the test of time. Although science proceeds by making use of the work that others have done before, it is not based on the assumption that everything that went before is correct. It is precisely because that there is always the possibility of errors that so much is based on ‘balance of evidence’ arguments’ that are mutually reinforcing.
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