Reverse Tribalism and Global Warming

An essay written for the Dot Earth blog of The New York Times by ThomasCrowley Climate Change and Reverse TribalismA recent synoptic-scale warming resulted in almost the entire Greenland Ice Sheet inmelt-phase -- a startling but perhaps not unique event (normally about half of the areaundergoes surface melting in any given summer) and due to unusually warm southerly airflow over the ice sheet.Almost as troubling as this undoubtedly transient extreme have been quick statements bysome scientists that this has happened before and is probably just natural variability.While prudence is essential in interpretation of extreme climate change events, it istroubling that there now seems to be almost a knee-jerk reaction towards invoking naturalvariability in followup statements.Such statements would seem reasonable except for the fact that we can already attributeglobal warming, and continental warming to human-induced greenhouse gas climatechange. Careful statistical work indicates this can be done with a considerable degree ofconfidence [in IPCC terminology, the warmings are "very likely" (90% probability) dueto manmade climate change].We would expect detection to sometimes spread into the more regional scale, which,because it is very noisy, is more difficult to formally detect and attribute to manmadeglobal warming (the extreme 2003 European heat wave is one example where the formalprocess has been successfully applied; the July 2012 Bulletin of the AmericanMeteorological Society has a recent issue addressing other examples).In the Greenland case, we already know we are in a phase of record warming over theUnited States, very low sea ice level levels in the Arctic, and above-normal temperaturesin Canada. Thus, Greenland is surrounded on one side, the upwind side, by record-reaching temperatures that look suspiciously like what would be expected from globalwarming as it penetrates into the very noisy level of regional scale climate change.Is it really appropriate to therefore make a kneejerk inference, without any seriousstatistical justification, that the present Greenland warming is likely natural variability(or, slightly differently, mention past variations without uttering the alternate possibility)?Furthermore, focusing on the proximal cause of the warming is less enlightening than itseems. Greenhouse gases do not warm the atmosphere in a vacuum - the warmingtriggers atmospheric circulation changes. Reflex attribution to high-pressure systems as acause dodges the question as to what made the atmospheric circulation change. Suchstatements are in a sense pseudo-interpretations; it is like saying that it is warm becausethe wind is blowing from the south.Of course a formal detection and attribution methodologies would need to be appliedbefore we could more confidently assess the greenhouse gas likelihood. But the counter-argument is not scientific prudence; it is putting blinders on to the point of being blind toall but a pinprick of light. It is like pulling rabbits out of a hat; it is seat-of-the-pantsreverse attribution.In my opinion, this and other examples are cases of reverse tribalism and represents

either a conscious or subconscious reaction to public, media, and congressional outcriesand pressure that border on intimidation (especially for government scientists, whoseagencies are vulnerable to retaliatory budget cuts) if one even mutters underneath theirbreath, like Galileo, "but it could also be global warming".I am not advocating some Chicken Little approach to interpreting record climate changeevents. I have no patience with climate hysteria and furthermore believe it does moreharm than good, because it invites reverse reactions that impair pubic acceptance of amore "reasonable" approach to addressing climate change.But if the geographic scale of a phenomena is very large, it does not seem at allinappropriate to say something like "the large geographic scale of the warming/melting isconsistent with what we expect from global warming, but the interpretation would haveto be more carefully tested to see if this particular event could be put in that category.Even if it cant, the warming is certainly consistent with what we expect to happen,although we wouldnt expect it to happen every year. It could be years or even decadesbefore it might reoccur.”But ignoring even the possibility of greenhouse gases as a cause of the observed warmingis like ignoring a dead canary in a mine shift or, worse, looking at the dead canary andconcluding that it died of natural causes.Thomas Crowley is a retired geologist and climate scientist now living in Scotland. TheCO2 rise in his lifetime is comparable to the postglacial CO2 rise that took almost tenthousand years to transpire. Virtually no one says that greenhouse gas increase had aminor/nil effect on late glacial climate change.

Reverse Tribalism and Global Warming

by Andrew Revkin on Oct 29, 2012

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