A raging controversy, one almost as hot as the record-breaking heat wave on the North American west coast, has broken out over a recent paper in the Journal of Geophysical Research (Atmospheres), a peer-reviewed periodical published by the American Geophysical Union (AGU).
Authors John McLean, Chris de Freitas and Bob Carter all have a long history of links to climate disinformation groups and associated PR campaigns (many of which lead back to Canadian spinmeister Tom Harris, director of the International Climate Science Coalition).
Now the trio have claimed that their analysis demonstrates that global warming is primarily a result of natural processes with little role for anthropogenic influences such as greenhouse gases.
A barrage of criticism has forced the authors and their champions to backpedal furiously. Along the way, a PDF of the paper has been removed from the New Zealand Climate Science Coalition (NZCSC) website, presumably to rectify an egregious copyright breach. Even worse, the NZCSC parent affiliate, the above-mentioned International Climate Science Coalition (ICSC), was caught substituting its preferred title for the actual one in its link to the paper.
And, of course, a look at the actual data clearly shows that the trio’s touted source of global warming, namely a 1976 “shift” in the El Nino Southern Oscillation (or ENSO), can not possibly account for the recent upward trend in temperatures. All this raises serious questions about JGR’s editorial processes, and leads to the inevitable conclusion that the paper should be withdrawn.
To be sure, much of the paper’s analysis is unremarkable. ENSO has long been recognized by scientists as the main source of short-term ( year-to-year) variability in mean global temperature. But as discussed in relevant posts at RealClimate and Tamino’s Open Mind, that fact has little bearing on the attribution of the warming trend, which is clearly anthropogenic.
Naturally, then, criticism has focused on various unsubstantiated claims by McLean et al, including this concluding sentence:
Finally, this study has shown that natural climate forcing associated with ENSO is a major contributor to variability and perhaps recent trends in global temperature, a relationship that is not included in current global climate models. [Emphasis added].
The authors also claimed that “trends” over the last 14 years were similar for global temperature and ENSO (as measured by the Southern Oscillation Index or SOI), but did not actually present any evidence for the assertion:
The post-1995 period illustrated in Figure 7c shows that the respective trends across the last 14 years will be very similar, albeit from 1997 onward the average global temperature anomaly is consistently slightly higher than the relationship would suggest.
In discussing ENSO and tropical temperature trends, the authors made this unequivocal (but unsupported) claim:
We have shown here that ENSO and the 1976 Great Pacific Climate Shift can account for a large part of the overall warming and the temperature variation in tropical regions.
In two press releases, the trio went even further. The first press release, entitled “Nature, Not Man, Is Responsible For Recent Global Warming”, was apparently produced by the New Zealand Climate Science Coalition and released through Marc Morano‘s Climate Depot website (a project underwritten by the anti-AGW pressure group Committee For a Constructive Tomorrow, better known as CFACT).
The same press release, which featured NZ “corresponding author” Chris de Freitas, was apparently pressed upon New Zealand columnist Paul Gorman by NZCSC “foundation member” Brian Leyland (who also serves as ICSC Secretary). [Hat tip to BigCityLib].
Here, Bob Carter claimed:
The close relationship between ENSO and global temperature, as described in the paper, leaves little room for any warming driven by human carbon dioxide emissions.
And lead author McLean chimed in:
When climate models failed to retrospectively produce the temperatures since 1950 the modellers added some estimated influences of carbon dioxide to make up the shortfall.
A second press release, this one from the Australian Climate Science Coalition (a second ICSC affiliate), was reproduced nearly verbatim at FarmOnline. Naturally, this release focused more on Aussie lead author McLean, who elaborated further on the implications of the study for climate models:
This paper shows that the missing component [of climate models] was the El Niño-Southern Oscillation (ENSO). The difference in output when using these two factors is that one predicts a continuing rise in temperature and the other predicts fluctuations according to the ENSO. The data particularly over the last 10 years indicates that the latter is correct.
Reaction, of course, was swift. RealClimate called the paper “atrocious”, while Tamino at Open Mind demonstrated that the “differencing” analysis technique employed completely removed any trends whatsoever.
Back in New Zealand, National Institute of Water and Atmospheric Research principal climate scientist James Renwick told Paul Gorman:
They have used their favourite versions of the radiosonde data and don’t discuss the possible issues with some of the radiosonde and satellite data. They try and confuse the year-to-year variation and they have deliberately taken out the trend in their analysis.
Renwick also said the conclusions were unsupported by the paper’s analysis.
[The concluding statements] strike me as being questionable at best, not based on anything that’s been shown. It is a real surprise it got through the peer review.
Picking up on the same theme, James Annan focused on what appeared to be a grievous lapse in editorial process at AGU journals. Commenters everywhere wondered how such a travesty could have been published. Annan’s answer seemed the most likely – that the AGU’s system of letting authors nominate reviewers was an “open invitation to game the system.”
It’s also worth noting that Chris de Freitas has been involved in editorial shenanigans before. Half the editorial team of the journal Climate Research, including chief editor Hans Van Storch, resigned in protest over the journal’s’ refusal to repudiate an anti-AGW piece that was accepted by de Freitas when he was an editor there. And one of the co-authors of that paper, Willie Soon, just happened to have been a reviewer of the de Freitas article published by the Bulletin of Canadian Petroleum Geology in 2002. [See PDF at p. 27].
Since he is the brother of the present CSPG Editor [Tim de Freitas], the paper was handled by one of our most capable Associate Editors, Dale Leckie, and review by Willie Soon, an Astrophysicist at the Harvard-Smithsonian Center for Astrophysics and Sonja Boehmer-Christiansen, the scientific editor of Energy and Environment and a climate scientist at the University of Hull, UK. These individuals are recognized globally for their contributions to climate research. They also recommended publication of the paper with minor revision. However, their names were not included in the acknowledgements at the end of the paper, which was an oversight.
Ah, yes, Sonja Boehmer-Christiansen, the “scientific” editor of the contrarians’ favourite periodical, Energy and Environment, is “recognized globally”, all right – mainly for her decision to publish McKitrick and McIntyre without even bothering with pesky peer review, not to mention the truly atrocious George-Ernst Beck paper on historical CO2 concentrations. Now that’s how to “game the system”!
Anyway, in the face of the unrelenting attacks, a third press release has now been issued, with control reverting to the NZCSC. (Interestingly, this is the only one of the three that is actually available in its original form).
In contrast with the claim of the first NZCSC release, entitled “Nature, Not Man, Is Responsible For Recent Global Warming”, the latest headline backpedals somewhat: “Compelling New Research Shows Nature Rules Climate”. The news item announcing the latest press release has the rather illogical title “Three Australasian Scientists Find AGW Link To Southern Oscillation”.
More hilarity awaits in the news release itself, as the authors actually claim that the whole exercise of “differencing”, with its attendant detrending, was only done to find the correct lag between the Southern Oscillation Index (SOI) and mean global temperature (MGT).
Regarding the various previous claims about “trends”, they have this to say:
The results in Figure 7 clearly show that the SOI related variability in MGT is the major contribution to any trends that might exist, although the McLean et al study did not look for this. The key conclusion of the paper, therefore, is that MGT is determined in most part by atmospheric processes related to the Southern Oscillation.
That’s it? That’s the “compelling” analysis that shows that a shift in ENSO “is responsible for recent global warming”?
While we absorb fully the fact that key findings of this paper are pretty much admitted by the authors themselves to be empty hand waving, here are a couple of other interesting footnotes.
- The link to the NZCSC version of the paper no longer works. Most likely, this is related to the fact that the NZCSC appeared to have been in egregious violation of the authors’ copyright agreement with the AGU. That agreement permits alternate electronic publication only of unformatted versions of published articles, and these must be hosted only at the authors’ personal websites.
- Even worse, in its original news item on the paper, the International Climate Science Coalition had actually substituted the title of the first press release for for the actual title in its link to the paper:
It’s worth noting that all three authors are “advisors” to the ICSC, a sort of umbrella group that brings together contrarians from Canada, the United Kingdom, Australia and New Zealand. The ICSC also has a special relationship with the New Zealand and Australian “coalitions” – all three websites are even hosted at the same service provider in Arizona.
But for now, we’ll leave the authors and their dizzying array of affiliations with various “science” lobby groups aside, as that subject deserves a post (at least) of its own.
Turning (at last) to the data, we now examine comparisons of the Southern Oscillation Index (SOI) and various measures of mean global temperature. As explained by the Australian Bureau of Meteorology, the SOI “is calculated from the monthly or seasonal fluctuations in the air pressure difference between Tahiti and Darwin.” Negative values generally indicate El Nino conditions associated with warming episodes; for that reason SOI and temperature are plotted on opposing axes. (For those interested, an ASCII version of monthly SOI values is available here).
A couple of additional notes: McLean et al use a scaling of about 4.3 SOI for each deg. C of tempertaure. Here we have used a slightly different scale, namely 5 SOI for each deg. C. Also we use a six-month shift in SOI. As we are mainly interested in comparing trends over decades, however, these small differences in scaling and shifting are of negligible import.
First we show annual SOI averages plotted against the two standard lower tropospheric temperature series (UAH and RSS).
This chart makes clear a fact obscured in the multi-panel monthly data presentation in McLean et al.: The SOI slight downward trend is manifestly opposite to the warming lower troposphere (LT) temperature trends. It is difficult to understand, then, how ENSO could possibly be driving global warming.
Nevertheless, we’ll examine various ways of correcting for volcanic cooling, which is apparent in 1982-4 (El Chichon) and 1991-3 (Pinatubo).
First we’ll consider the recent period 1996-2008, which is free of major volcanic influence. This is the period in which McLean et al claimed to diiscern “similar” trends for SOI and mean global tempertaure. Recall also their related claim in the latest press release that their results “clearly showed that SOI related variability in MGT is the major contribution to any trends that might exist.” [Emphasis added].
The monthly series is obscured by wide variation. Nevertheless, over this period SOI is very slightly downward (indicating cooling influence), while both UAH and RSS have warming trends above 0.1 deg C per decade.
The annual plot is clearer, and shows a virtually flat SOI against rising LT temperatures:
Finally, we’ll take a look at decade-over-decade changes in SOI and global average temperature (this time, we’ll include surface global tempertaure as well, with series from HadCRU and NASA GISTEMP). The first chart shows a clear upward trend in all temperature series, while SOI rises slightly in the 1990s, but falls back in the 2000s.
Even if we remove the years of significant volcanic cooling, there is still no evidence of a dominant ENSO influence on temperature trends. The most that could be said is that variations in SOI may have had a slight dampening effect on warming in the tropospheric data sets, but even thatsmall effect is not evident in the decadal surface record.
To sum up:
- The McLean, de Freitas and Carter paper presented unsubstantiated conclusions that are contradicted by a cursory analysis of the very data presented.
- There is widespread agreement among climate scientists that this paper should not have passed review and should not have been accepted for publication.
- The authors actively participated in a deceptive public relations campaign that trumpeted and exaggerated the paper’s claims, a campaign that even substituted a press release headline for the true title of the paper.
- The authors permitted an egregious breach of copyright in the dissemination of the paper in its published form at the New Zealand Climate Science Coalition website.
What more is needed to prod the AGU and the Journal of Geophysical Research to do the right thing? The paper should be withdrawn, and the editor responsible disciplined. Now.