I’m feeling a little less grumpy about blog crashes which were wearing me out. I’ll obviously be commenting on AR4 but I’m not sure where I want to start. While I was researching some material, I came across an interesting comment in James Elsner’s occasional blog (only a few posts per year) about adjustments to hurricane wind speeds – a hot topic in the hurricane wars – which ties back to a thread from Willis in October about Elsner et al 2006.
Elsner, a frequent author on hurricanes, stated at his blog:
The debate on hurricanes and climate change can sometimes devolve into issues of data reliability. Unfortunately, some of what is said about these issues is nonsense, or worse, self serving. As one example, during the middle 1990′s, the high priest of NOAA’s best-track data argued vehemently that the hurricane intensities during the 1950′s and ’60s were biased upward. I checked with my colleague Noel LaSeur, who flew into these early storms, and he said “If anything, we underestimated the intensity” suggesting a possible downward bias. Noel is correct. With this light, the intensity of the hurricanes of 2004 & 2005 is not that unusual against the backdrop of the formidable mid century hurricanes. Enthusiasts and partisans should not be tinkering with these data. Moreover, while it stands to reason (a priori) that the historical information will be less precise than data collected today with modern technologies, to ignore these earlier records is scientifically indefensible. Inspired by Edward Tufte recommendations for truth-telling in graphical presentations (Visual Explanations, Graphics Press, 1997), I suggest that one way to enforce data standards is to insist that the original, unprocessed data be posted alongside the manipulated data, and that the manipulators and their methods be identified.
I agree 1000% with Elsner’s attitude towards data adjustments – the reference to Tufte also leads to many extremely interesting analyses. In proxy studies, all too often, the adjustments are often poorly or inaccurately described and can only be discerned through patient dissection of the data. Further, all too often, the adjustments are as large or larger than the effect being measured. So the policy towards showing both versions makes eminent sense.
However, in respect to the controversy initiated here, as so often in climate science, one feels that one has fallen down a rabbit hole. I presume that the “high priest” in question is Landsea, the author of Landsea 1993, which proposed a downward adjustment of Atlantic wind speeds from 1945 to 1969. Despite Elsner’s excoriation here, Landsea appears to have resiled somewhat from the adjustment proposed 14 years ago, saying in his Reply to Emanuel 2005:
It is now understood to be physically reasonable that the intensity of hurricanes in the 1970s through to the early 1990s was underestimated, rather than the 1940s and 1960s being overestimated.
On the other hand, the adjustment is alive and well in Emanuel 2005, Webster et al 2005 and Holland and Webster 2007, all of which go uncriticized by Elsner. Indeed, the results of Emanuel 2005 depend to a very considerable extent on the adjustment. But no mention of this by Elsner. I discussed the Landsea adjustment here and here .
Elsner himself fails to adhere to the above policy in the recent Elsner et al 2006, High frequency variability in hurricane power dissipation and its relationship to global temperature, discussed by Willishere. They state:
It is well known that hurricane data from the Atlantic basin are not uniform in quality owing to improvements in observational technology over the years. We adjust the pre-1973 wind speeds to remove biases using the same procedure as described in Emanuel (2005) and compute the PDI by cubing the maximum wind speed for each 6-h observation…. For comparisons we perform the analysis using both the adjusted and unadjusted wind speeds.
Sounds good. But the analysis with both versions is nowhere to be found. Instead we see the following graphic of a single version (actually showing the cube root of the PDI – or a simple integral of the wind speed – a point observed by Willis previously):
Elsner et al 2006 Figure 2 top panel.
To make it more confusing, there is no discussion of whether this is the adjusted or unadjusted version? In his earlier post, Willis couldn’t figure it out, observing that i seemed to be neither:
Second, I haven’t a clue what they’ve done with their PDI data. They say they got it from HURDAT, but it looks nothing like my calculation of the PDI from HURDAT. It also looks nothing like Emanual’s PDI, or Landsea’s PDI. Elsner says: “We adjust the pre-1973 wind speeds to remove biases using the same procedure as described in Emanuel (2005) …” but this is not the case. Here’s the difference.
Figure from Willis’ post.
Back to Elsner’s blog, where he stated:
I suggest that one way to enforce data standards is to insist that the original, unprocessed data be posted alongside the manipulated data, and that the manipulators and their methods be identified.
Good idea. Elsner et al 2006 would be a good place to start.