Michael Mann and Gavin Schmidt
[update 3/20/07: The New York Times has run a short letter from us w/ a link to RealClimate for more info (scroll down to 5th letter; the 2nd letter from James McCarthy of Harvard is quite good too, as are some of the others).]
The first rule when criticizing popular science presentations for inaccuracies should be to double check any ‘facts’ you use. It is rather ironic then that William Broad’s latest piece on Al Gore plays just as loose with them as he accuses Gore of doing.
We criticized William Broad previously (Broadly Misleading) for a piece that misrepresented the scientific understanding of the factors that drive climate change over millions of years, systematically understating the scientifically-established role of greenhouse gases, and over-stating the role of natural factors including those as speculative as cosmic rays (see our recent discussion here). In this piece, Broad attempts to discredit Gore’s “An Inconvenient Truth” by exaggerating the legitimate, but minor, criticisms of his treatment of the science by experts on climate science, and presenting specious or unsubstantiated criticisms by a small number of the usual, well-known contrarians who wouldn’t agree even if Gore read aloud from the latest IPCC report.
Broad starts out by quoting Don Easterbrook (Western Washington University) with a statement,
there are a lot of inaccuracies in the statements we are seeing, and we have to temper that with real data.
Thrown in for good measure is a similarly poorly-supported quote by Kevin Vranes (who is referred to as a climatologist, but who now works on science policy) that
questioned whether his [Gore’s] presentations were overselling our certainty about knowing the future.
Unfortunately, neither Easterbrook’s inaccuracies nor Vranes oversold certainties are mentioned. We reviewed the movie ourselves, looking hard for such ‘inaccuracies’, and could only find one minor area (the explanation of the complex relationship between the global surface temperatures and greenhouse gas concentrations over glacial/interglacial cycles) where justified criticism might be levied (and here, the accusation was only that Gore simplified a complicated relationship, something that is arguably unavoidable in a movie intended for mass popular consumption).
Broad then draws upon the same false dichotomy used previously which seems to equate the mainstream of scientific opinion (that global warming and climate change is real, almost certainly in large part anthropogenic, and likely to lead to substantial and potentially deleterious changes in our environment if no action is taken to reduce greenhouse gas emissions) with “alarmism”, and places contrarians at the very fringe of scientific thinking on an equal footing with mainstream scientists. He goes on to trot out a number of the usual suspects, reciting the usual specious claims and half-truths.
Among the worst, is this one
Mr. Gore, who highlights the devastation of Hurricane Katrina and cites research suggesting that global warming will cause both storm frequency and deadliness to rise. Yet this past Atlantic season produced fewer hurricanes than forecasters predicted (five versus nine), and none that hit the United States.
This is dishonest in at least two different ways. First of all, Broad conveniently forgets to mention that the 2006 Hurricane season was accompanied by a moderate El Nino event. It is well known that El Nino events, such as the 2006 El Nino, tend to be associated with stronger westerly winds aloft in the tropical Atlantic, which is unfavorable for tropical cyclone development. The season nonetheless produced a greater than average number of named storms in the tropical Atlantic (10), 3 more than the typical El Nino year. But El Ninos come and go–more or less randomly–from year to year. The overall trend in named tropical Atlantic storms in recent decades is undeniably positive. We can have honest debates about the long-term data quality, but not if we start out by misrepresenting the data we do have, as Broad chooses to. Additionally, this is a clear misrepresentation of what Gore actually stated in his book. Gore indicated that it is primarily Hurricane intensities which scientists largely agree should be expected to increase in association with warming surface temperatures, and specifically notes that
There is less agreement among scientists about the relationship between the total number of hurricanes each year and global warming.
Next. Roy Spencer, best known for his satellite work arguing against warming of the atmosphere (which turns out to have been an artifact of a combination of algebraic and sign errors), criticizes Gore for pointing out that recent warmth appears to be anomalous in at least the past 1000 years. Spencer does this by both mis-characterizing the recent National Academies Report on the subject which indeed pointed out that there are numerous lines of evidence for precisely this conclusion, and by completely ignoring the recently-released IPCC Fourth Assessment report, which draws the stronger conclusion that the warmth of recent decades is likely anomalous in at least the past 1300 years.
We also find it amusing that Broad takes anything Robert Carter has to say seriously, given that he doesn’t even believe that current rises in CO2 are human caused (judging from his Senate performance). Sea level rise statements from the IPCC Summary are horribly mischaracterised. Easterbrook’s implication that global temperatures have varied by more the 20 times the medieval temperature anomaly over the Holocene is simply laughable (only if you include the deglaciation might that be true, but since that was before the onset even of settled human communities it seems less than relevant).
This article is very disappointing, not just because it gets things so wrong, but because it misses an opportunity to address a much more substantive issue. It is inevitable that working scientists will find popular presentations of their work lacking in depth and nuance (after all, depth and nuance are what we do!). Whatever you may think about Al Gore’s movie, it is indisputable that it has raised awareness of the issues and left a substantial part of the public hungry for more information. That hunger can only be fed by people who are closer to the science than Gore, and it is inevitable that the AIT will be used as a springboard or contrast for further presentations. A better article would have investigated how that is happening and how that is affecting public awareness of the science. Unfortunately, this article does nothing to improve public awareness, and that is deeply ironic.
[Hat tip to David Roberts for pointing out his own article on the Broad piece. David picks up on some additional morsels we left out]