Roger Pielke, Jr. took a lot of heat for his claim at 538.com that increased costs from storm damages aren’t being driven by anthropogenic global warming. As Pielke wrote;
When you read that the cost of disasters is increasing, it’s tempting to think that it must be because more storms are happening. They’re not. … the numbers reflect more damage from catastrophes because the world is getting wealthier. We’re seeing ever-larger losses simply because we have more to lose …
… Fortunately, scientists have invested a lot of effort into looking at data on extreme weather events, and recently summarized their findings in a major United Nations climate report, the fifth in a series dating back to 1990. That report concluded that there’s little evidence of a spike in the frequency or intensity of floods, droughts, hurricanes and tornadoes.
Pielke was widely criticized. MIT’s Kerry Emanuel was given space at 538 to say that he’s ” not comfortable with Pielke’s assertion that climate change has played no role in the observed increase in damages from natural hazards” and does not “see how the data he cites support such a confident assertion.”
ThinkProgress had a good roundup of scientific critics, including Jennifer Francis;
It’s ludicrous to say that extremes have not increased, and they have certainly increased in ways that are completely consistent with expectations based on atmospheric physics and climate model projections in response to increasing greenhouse gases;
Pielke’s piece is deeply misleading
This is the same old wrong Roger…He is demonstrably wrong and misleads;
and John Abraham says Pielke is wrong because “we have already detected significant increases in Atlantic hurricane intensity, in extreme heat waves, large precipitation events and regional droughts.”
Pielke claimed to be consistent with the latest IPCC report, so what does it actually say about the issue? Fortunately, it’s available on-line, and I direct your attention to chapter 10.
10.6.1.5 Tropical Cyclones
AR4 –[note: the IPCC’s 4th Assessment Report—the one preceding this one] concluded that ‘anthropogenic factors more likely than not have contributed to an increase in tropical cyclone intensity’ (Hegerl et al.,2007b). Evidence that supports this assessment was the strong correlation between the Power Dissipation Index (PDI, an index of the destructiveness of tropical cyclones) and tropical Atlantic SSTs [note: sea surface temperatures] (Emanuel, 2005; Elsner, 2006) and the association between Atlantic warming and the increase in GMST (Mann and Emanuel, 2006; Trenberth and Shea, 2006). Observations suggest an increase globally in the intensities of the strongest tropical cyclones (Elsner et al., 2008) but it is difficult to attribute such changes to particular causes (Knutson et al., 2010). The US Climate Change Science Program (CCSP; Kunkel et al., 2008) discussed human contributions to recent hurricane activity based on a two-step attribution approach. They concluded merely that it is very likely (Knutson et al., 2010) that human-induced increase in GHGs has contributed to the increase in SSTs in the hurricane formation regions and that over the past 50 years there has been a strong statistical connection between tropical Atlantic SSTs and Atlantic hurricane activity as measured by the PDI. Knutson et al. (2010), assessed that ‘…it remains uncertain whether past changes in tropical cyclone activity have exceeded the variability expected from natural causes.’ Seneviratne et al. (2012) concurred with this finding
I pause here to direct your attention to two things. First, note that this is a review of the relevant literature, and that the sections I have bolded show disagreements in that literature. Second, note that several of the names linked to criticism of Pielke show up here, Mann, Emanuel, and Trenberth. Look more closely and you’ll note that their names are attached to studies that show a link between AGW and storm strength, and not to the studies that are more doubtful about such a link. No doubt Mann, Emanuel and Trenberth are confident in their findings, but the IPCC report itself demonstrates that there is a lack of consensus on those findings. So when they attack Pielke for misrepresenting the data, there’s reason to believe the real criticism is that he finds Knutson’s and Sneviratne’s findings more persuasive.
Let’s continue with the IPCC report, picking up with the next paragraph.
Studies that directly attribute tropical cyclone activity changes to anthropogenic GHG emission are lacking.
I want to emphasize this first line. There are a number of studies, and presumably good ones, that indirectly link AGW to storm activity, but we are lacking in studies that directly show such a link. Now I’d like you to do a quick thought experiment. If you went to just about any left-of-dead-center blog and commented that “studies directly attributing cyclone activity to AGW are lacking,” what kind of response do you think you’d get? My hypothesis is that you’d get a response that indicates the IPCC report denies the existence of AGW.
Among many factors that may affect tropical cyclone activity, tropical SSTs have increased and this increase has been attributed at least in part to anthropogenic forcing (Gillett et al., 2008a) However, there are diverse views on the connection between tropical cyclone activity and SST (see Section 14.6.1 for details). Strong correlation between the PDI and tropical Atlantic SSTs (Emanuel, 2005; Elsner, 2006) would suggest an anthropogenic influence on tropical cyclone activity. However, recent studies also suggest that regional potential intensity correlates with the difference between regional SSTs and spatially averaged SSTs in the tropics (Vecchi and Soden, 2007; Xie et al., 2010; Ramsay and Sobel, 2011)
I’m breaking in on the middle of the sentence here to note that Pielke-critic Emanuel appears again, as the author of a paper showing strong correlation, but other recent studies aren’t fully supportive of that finding.
and projections are uncertain on whether the relative SST will increase over the 21st century under GHG forcing (Vecchi et al., 2008; Xie et al., 2010; Villarini and Vecchi, 2012, 2013)
“[P]rojections are uncertain” about whether AGW will increase relative sea surface temperatures. Sea surface temperatures affect cyclone formation and strength, so if we have uncertainty in our projections of the effect of AGW on sea surface temperatures, then we have uncertainty in our projections about what effect AGW will have on cyclones. This is a matter of formal logic (although, of course, we may develop more certainty in future studies).
Jumping the remainder of that paragraph and the next (a discussion of aerosol forcing’s affect on storm formation), we come to the conclusion of this section:
Globally, there is low confidence in any long-term increases in tropical cyclone activity (Section 2.6.3) and we assess that there is
low confidence in attributing global changes to any particular cause. In the North Atlantic region there is medium confidence that a reduction in
aerosol forcing over the North Atlantic has contributed at least in part
to the observed increase in tropical cyclone activity since the 1970s.
There remains substantial disagreement on the relative importance of
internal variability, GHG forcing and aerosols for this observed trend.
It remains uncertain whether past changes in tropical cyclone activity
are outside the range of natural internal variability.
Let’s go back to Pielke’s argument, which is that increasing financial costs of storm damage from hurricanes (cyclones) is a consequence of humans having built up a greater amount of vulnerable infrastructure in storm-prone areas, and not from an increase in hurricane frequency or strenght. For this he is branded an AGW denier who is dabbling in pseudoscience, and labeled “demonstrably wrong,” “misleading” and “ludicrous.”
But Pielke’s position is demonstrably within the stated conclusions of the IPCC’s latest report. That doesn’t mean he’s right. His critics research may in the end prove to be accurate. But at present, that is in scientific dispute. There are peer reviewed findings sufficient for the reviewers writing this section of the IPCC report–the section that directly bears on the issue about which Pielke wrote–to assert,
There is low confidence in attribution of changes in tropical
cyclone activity to human influence owing to insufficient observational evidence, lack of physical understanding of the links between anthropogenic drivers of climate and tropical cyclone activity and the low level of agreement between studies as to the relative importance of internal variability, and anthropogenic and natural forcings.
Abraham’s response to Pielke’s reliance on the IPCC report is;
the panel, which is referring to an “absence of an attributable climate change signal,” has set a high scientific bar for itself. Detecting climate signals in normalized economic losses remains deeply contested, but trends in extreme weather itself can be studied directly, a field around which there is much consensus.
This is, it seems to me, misleading. First, it is odd for a scientist to critique the setting of a high bar for evidence, or to imply that really we ought to accept a lower bar. Second, he seems to suggest that the IPCC panel was just reviewing studies that looked for climate signals in economic losses, which is simply untrue. The IPCC panel included Abraham’s research, but they also included research that didn’t verify his, and that research was not based on economic data, either.
It seems that a peaceful, non-vitriolic discussion of AGW is not possible in today’s political climate…not even if you correctly quote the IPCC reports.
[Image source: Wikimedia Commons]