In the context of global warming, the term "lukewarmers" refers to individuals who accept the scientific reality that human greenhouse gas emissions are a primary cause of the current global warming, but who believe that future global warming and the consequences of the associated climate change will not be as bad as the body of scientific evidence indicates. Different "lukewarmers" have different justifications for this belief, but in general, for one reason or another they tend to find the evidence for relatively mild future climate change impacts more compelling than the evidence to the contrary.
Despite his lack of climate expertise, one of the most prominent self-proclaimed "lukewarmers" featured in the media is Matt Ridley, a science writer, businessman, and poor risk manager. In its September 2012 edition, WIRED magazine published an article in which Ridley wrongly argued that virtually every environmental concern over the past half century has been overblown, and therefore concern about climate change must also be overblown. Skeptical Science debunked that article, and that debunking was quoted in the November 2012 edition of WIRED, which also featured excerpts from some other letters and articles both praising and criticizing Ridley's piece.
Recently, Ridley attempted to address some of the many criticisms of his WIRED article. In the process, he provided further evidence that "lukewarmer" positions tend to stem from ignoring most scientific research which does not support the desired conclusion — that the consequences of climate change will be relatively benign. He then proceeded to cement that evidence by publishing a list of 10 'tests' that would persuade him that climate policy makes sense. This document was published on the website of the climate science denying Global Warming Policy Foundation, and the references Ridley cited therein are almost exclusively from climate science denying blogs.
In his response to the criticisms of his WIRED piece, Ridley defended his irrational climate optimism by arguing that "some of the subplots of climate change have already proved exaggerated." He lists a few examples that he views as "exaggerated subplots":
Clearly these are very weak points in supporting the argument that climate concerns are "exaggerated." Meanwhile Ridley fails to mention the climate consequences which are occurring faster than expected, and climate scientists are already being too conservative in many of their predicitons, erring on the side of least drama.
Ironically, Ridley also argued that even though sea level is rising at a rate at the very upper end of the IPCC projections, that sea level data support his argument because, he argues, sea level rise has been decelerating. To support this claim, Ridley pointed to a blog post by Patrick Michaels, in which Michaels lived up to his reputation by deleting inconvenient data.
Although his blog post was written in September 2012, Michaels (who likewise might be considered a "lukewarmer") only examined global mean sea level data for 1993 through 2011. Global mean sea level rise has been accelerating over the past 150 years; however, the preponderance of La Niña events over the past 5 years and recent extreme flooding has caused a short-term slowing of the sea level rise.
Michaels and Ridley thus ignore the accelerating sea level rise over the past 150 years to argue that the rise is decelerating based on just a few years' worth of noisy data. This type of argument has come to be known as going down the up escalator. In the data over the past year which are conveniently excluded by Michaels and Ridley, global sea levels have risen rapidly as we have transitioned away from a La Niña phase (Figure 1).
Figure 1: University of Colorado global mean sea level data (seasonal signal removed, inverse barometer applied) with a 12-month running average through 2011 (blue) and January–November 2012 (red).
This is far from the first time that "lukewarmer" Pat Michaels has deleted inconvenient data, and Stoat has another example of Ridley caught red handed doing the same thing.
In both his WIRED response and 'ten tests' document, Ridley claims there is no evidence that water vapor will significantly amplify global warming. He is wrong – see our discussion here, a list of relevant scientific papers here, and a new paper by Dessler (2012) here. The scientific literature and data consistently show that the water vapor feedback is a positive strong one, as we expect based on fundamental atmospheric physics.
However, for some reason Ridley continues to lump the cloud feedback in with the water vapor feedback. The cloud feedback remains one of the largest uncertainties in climate science; Ridley claims there is evidence that the cloud feedback will significantly dampen global warming, but provides no references to support his assertion.
In his WIRED response, Ridley does reference Gillett et al. (2012), which did not investigate the water vapor feedback. The study found a relatively low net climate sensitivity (and thus a relatively low net feedback) when considering temperature data from 1851 to 2010, but found a sensitivity and feedback consistent with IPCC values when considering temperature data from 1901 to 2000. The fact that their results differ while using different but overlapping timeframes is something of a red flag, and Gillett et al. specifically cautioned against over-interpreting their results.
"We therefore recommend caution in interpreting the scaled projections derived from this single model..."
Clearly Ridley did not heed their warning. The body of scientific literature remains consistent with a climate sensitivity in the range of 2 to 4.5°C surface warming in response to a doubling of CO2, which means that the net feedback will be strongly positive, amplifying global warming.
The remainder of Ridley's ten 'tests' involve:
In every argument Ridley has ignored the inconvenient data and relied exclusively on information from climate denialist blogs, and he has presented the "lukewarmer" case as being based on a laundry list of long-debunked climate myths.
Ultimately the "lukewarmers" may be right, climate sensitivity may be on the lower end of the range of possible values, and maybe we will have sufficient time to reduce our greenhouse gas emissions enough to prevent catastrophic climate change. But if the "lukewarmers" are right, it will not be because the temperature record is wrong, or because global warming magically stopped 16 years ago, or because aliens are driving SUVs on Mars, or any of these long-debunked myths.
If the "lukewarmers" like Ridley are right, it will be because we were very lucky that climate sensitivity happened to be near the bottom of the range of possible values, and because we eventually managed to reduce our greenhouse gas emissions despite efforts by people like Ridley to delay that from happening. And if we are not so lucky, and catastrophic climate change does occur, history will not look kindly on the "lukewarmers" like Ridley who helped make it happen by cherrypicking data, ignoring inconvenient evidence, and persuading others to follow their preferred haphazard climate path.
Posted by dana1981 on Monday, 11 February, 2013
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