Much Ado About Little

By Philip Duffy

Public criticism of the IPCC is getting pretty silly.

The first issue to come up involved an incorrect estimate of the melting rate of nine Himalayan glaciers (out of over 9,000); the IPCC cited an article including this error. This happened because the IPCC’s procedures were not followed, which is inexcusable. But to say that this undercuts the idea that humans are changing climate is a stretch, to put it mildly. The vast majority of glaciers in the world are shrinking, including these. It’s just that these 9 are not shrinking as fast as the IPCC reported.

Then there’s the truly horrifying error involving how much of the Netherlands is already below sea level. Can somebody please explain to me what that has to do with climate science? If the IPCC misreported the height of Mt. Everest, would that mean that greenhouse gases are actually harmless? If this kind of stuff is the best the critics can come up with—out of THOUSANDS of pages of dense scientific text—then I feel awfully good about the IPCC.

A hilarious (not really) “controversy”  was manufactured around a paper that made estimates of sea level rise that supported those of the IPCC. The paper’s method (but not the IPCC’s) turned out to be flawed, and the paper was withdrawn by its authors after other scientists pointed out the mistakes. This has been widely hailed as an error (or worse) by the IPCC, even thought the paper was published two years after IPCC’s assessment, and used a different approach. One blog even announced “Sea level not rising.”

Other media have described new, higher, estimates of sea level rise as ‘another IPCC mistake’. Even if this were a mistake (I am going to argue it’s not), are we supposed to believe that the IPCC is dishonest because sea level is rising faster than they said???

A more subtle point has to do with what “wrong” means in this context.  When the most recent IPCC estimates of sea level rise were prepared, the authors knew that they could not accurately predict the contribution from future melting of Greenland ice. So they deliberately used a low-end estimate of this contribution, and said that this is what they were doing. (Many climate-change deniers conveniently ignored this fact, however.)  More recent estimates of future sea level rise are more pessimistic, largely because new measurements show more rapid melting of Greenland. This is how science is supposed to work: our understanding evolves. Were the old estimates “wrong?” Probably; we’ll see. (Actually, our kids will. I, for one, plan to be busy decomposing.) But was the IPCC “wrong” to cite these estimates? No! The mission of the IPCC is to accurately summarize current understanding of climate science, societal impacts, and mitigation. (Actually, because thorough reviews take a long time, what appears in the IPCC is not quite current.) The IPCC’s sea level rise estimates were arguably the best we knew at the time. So it’s not a “mistake” that they seem now to be too low: it’s progress. By contrast, the Himalayan glacier boo-boo clearly is a mistake, because the IPCC did not report the best knowledge of the time.

So let’s not confuse real mistakes with the normal progress of science.