OR: DENIALIN’ AIN’T EASY
Monday, like any other day, was a pretty miserable one to be a climate denialist.
As with Intelligent Design proponents (née Creation Science proponents, née Creationists), 9/11 Truthers, the anti-vax loons, et al., in order to give themselves the appearance of credibility, climate denialists have to simultaneously wrap themselves in the vestments of science while rejecting what the science actually says. It is, as you can imagine, an entirely unconvincing act.
The evidence that man-made processes, notably our emissions of greenhouse gases, are warming the planet and altering the climate has grown astoundingly in the 30 years since the National Academies of Science-commissioned Carbon Dioxide and Climate: A Scientific Assessment. Each week, evidence pours in in the form of primary scientific literature documenting the changes to our climate, their already-significant impacts on plants and animals, and so on. Calls to cut GHG emissions are heard from the science academies of nations around the world. There is, to put it mildly, a stunning lack of scientific evidence suggesting we should keep on as we are and expect no fallout.
Hence you get Serious Thinkers like Jonah Goldberg asserting that, despite a study’s lead author’s clear statement that his paper on sunspots has nothing to do with anthropogenic warming, we should in fact believe it has something to do with- and indeed undermines- our understanding of anthropogenic warming. There are only a few avenues open to denialists who seek to keep up the charade that they care about science: attempt to discredit the actual science and substitute their own bloggy version, champion studies that are tremendously flawed, clumsily misrepresent papers that don’t actually challenge the undeniable reality of anthropogenic warming, or some combination thereof.
Enter Kyle Swanson and Anastasios Tsonis.
Swanson and Tsonis have been exploring an apparent series of climatic regime changes (marked by the synchronization, coupling, and decay on multidecadal scales of naturally variable climate features) superimposed on the long term warming trend of the 20th century (e.g. here and here). They think that the existence of these regimes might better explain some features of the temperature record than the mechanisms usually invoked (e.g. mid-century cooling via sulfate production). Naturally, their hypothesis has been seized upon by a denialosphere desperate for anything that seemingly challenges the mainstream on global warming (e.g. here, here, here, etc.) and touted as evidence that “the science isn’t settled”, “nature not humans controls the climate”, and similar rubbish. Thus Swanson and Tsonis became a sort of fig leaf behind which the denialists sought to conceal their anti-science beliefs.
For its part, the reaction from the larger climate science community has been along the lines of, “interesting, but absent any physical explanation, not entirely convincing at the present” and it was repeatedly pointed out that Swanson and Tsonis’s work wasn’t saying anything like what the denialists imagined it to. In the interests of clarifying some misconceptions, RealClimate recently hosted a guest post by Swanson. There, Swanson points out that those attempting to use any findings of increased influence of natural variability over the 20th century as a rebuttal to concerns over enhanced greenhouse warming couldn’t be more wrong; a climate system more sensitive to natural variability is one also that will respond more strongly to anthropogenic forcing:
A climate that is highly sensitive to radiative forcing (i.e., responds very strongly to increasing greenhouse gas forcing) by definition will be unable to quickly dissipate global mean temperature anomalies arising from either purely natural dynamical processes or stochastic radiative forcing, and hence will have significant internal variability. The opposite also holds.
In a new paper published this week in the early edition of the journal PNAS entitled Long-term natural variability and 20th century climate change (or here), Swanson and Tsonis, along with coauthor George Sugihara (from here on “SGT”), have attempted to address more explicitly the mechanism by which this enhanced natural variability hypothesis might work and its impact on the 20th century temperature record.
In the paper, SGT make a point to highlight the same argument made by themselves and others in response to specious (denialist) claims that their findings mean anthropogenic warming is as a result less of a concern:
Viewed in this light, the lack of modeled compared to observed interdecadal variability may indicate that current models underestimate climate sensitivity.
Reiterating that a climate system highly sensitive to natural variability is one also that will respond more strongly to anthropogenic forcing. A higher climate sensitivity would mean, for example, that the IPCC estimates of ~3°C warming in response to doubled CO2 are too optimistic. Continue reading