Climategate: The Real Story - The Hockey Stick and the Climate Wars - page 146

reconstruction of past temperatures to be viewed in the context of the most recent warming. The
separate curves for the proxy reconstruction and instrumental temperature data were clearly labeled,
and the data for both curves were available in the public domain at the time of publication for anyone
who wanted to download them.
That, in short, was the “trick” that Jones had chosen to use to bring the proxy temperature series
in his comparison up to the present, even though the proxy data themselves ended several decades
earlier. There was one thing Jones did in his WMO graph, however, that went beyond what we had
done in our Nature article: He had seamlessly merged proxy and instrumental data into a single curve,
without explaining which was which. That was potentially misleading, though not intentionally so; he
was only seeking to simplify the picture for the largely nontechnical audience of the WMO report.
After its own inquiry, Nature editorialized on the flap over “trick”: “One e-mail talked of displaying
the data using a 'trick'—slang for a clever (and legitimate) technique, but a word that denialists have
used to accuse the researchers of fabricating their results. It is Nature 's policy to investigate such
matters if there are substantive reasons for concern, but nothing we have seen so far in the e-mails
qualifies.” 19
What about “hide the decline”? Or to be more precise, the phrase “for Keith's to hide the
decline,” referring to Keith Briffa and the Briff a et al. temperature reconstruction. 20 As discussed
briefly in chapter 7 , this particular reconstruction was susceptible to the so-called divergence
problem, a problem that primarily afflicts tree ring density data from higher latitudes. These data
show an enigmatic decline in their response to warming temperatures after roughly 1960, perhaps
because of pollution 21 —that is the decline that Jones was referring to.
While “hide the decline” was poor—and unfortunate—wording on Jones's part, he was simply
referring to something Briffa and coauthors had themselves cautioned in their original 1998
publication: that their tree ring density data should not be used to infer temperatures after 1960
because they were compromised by the divergence problem. Jones thus chose not to display the
Briffa et al. series after 1960 in his plot, “hiding” data known to be faulty and misleading—again,
entirely appropriate.
MBH98/MBH99 and many other reconstructions since, by contrast, use few such tree ring
density records and thus do not suffer—at least obviously—from the decline that Jones was referring
to in his e-mail. Individuals such as S. Fred Singer have nonetheless tried to tar my coauthors and me
with “hide the decline” by conflating the divergence problem that plagued the Briffa et al. tree ring
density reconstruction with entirely unrelated aspects of the hockey stick. Singer, for example,
claimed 22 that we had ended our reconstruction in 1980 to hide a lack of warming, when the reason—
as clearly stated in MBH98 23 —was that many of our proxy data terminated at or close to 1980; there
could be no reconstruction later than 1980 in our case.
Climate change deniers made other allegations based on the leaked e-mails. They claimed, for
example, that the e-mails showed that CRU had destroyed original instrumental surface temperature
records, or had blocked access to public data. Both charges were false, their apparent basis being
that some hard-copy printouts had been lost during a move decades earlier, though the data
themselves were all preserved, and that CRU was not at liberty to release a restricted subset of
temperature records that some other countries had provided because of contractual obligations not to
release those data to third parties. These allegations were nonetheless used to undermine confidence
in the instrumental surface temperature record. It was convenient for the attackers to ignore the fact