The Decline They Hid: the Deleted Portion of the Briffa Reconstruction
Real climate scientists are sifting out the details of the data to which CRU director and warmist Phil Jones applied fellow warmist Michael Mann's 'Nature trick...to hide the decline...'.
The hidden data is that of Keith Briffa, a fellow climate scientist (and warmist) at East Anglia. Briffa compiled tree-ring data to obtain global temperature estimates back to 1400. But there was a problem with the tree-ring data, from the warmist perspective. The tree ring data showed pronounced cooling beginning in the mid-20th century. This was at variance with some ground temperature measurements (so we are told- the actual raw data from the ground stations was 'accidently' thrown in the garbage in the 1980's, and all we have are 'modified' data from the CRU scientists themselves.)
So the method that the warmist climate scientists used to estimate temperatures over the past millenium or so (tree ring data) did not show warming that correlated with rising CO2. This leaves a couple of possibilities, neither favorable to the warmist hypothesis. Either the tree ring data in the 20th century that was inconsistent with temperature recordings meant that the older tree ring data was unreliable (eliminating the argument that the warming was unprecedented) or the temperature recordings were inaccurate (perhaps from the heat island effect, in which sensors situated near growing urban areas give spurriously high readings) and rising CO2 didn't cause warming.
What to do?
Simple. Delete the tree rign data beginning in the mid-20th century, when the cooling became pronounced, and use (already CRU 'modified') ground station data more supportive of the warmist hypothesis in it's place.
Climate scientist and skeptic Steve McIntyre:
"Hide the decline" refers to the decline in the Briffa MXD temperature reconstruction in the last half of the 20th century, a decline that called into question the validity of the tree ring reconstructions. (I'm going to analyze the letters on another occasion.) In the IPCC Third and Fourth Assessment Reports, IPCC "hid the decline" by simply deleting the post-1960 values of the troublesome Briffa reconstruction - an artifice that Gavin Schmidt characterizes as an "a good way to deal with a problem" and tells us that there is "nothing problematic" about such an artifice (see here.
Not only were the post-1960 values of the Briffa reconstruction not shown in the IPCC 2001 report - an artifice that Gavin describes as being "hidden in plain sight", they were deleted from the archived version of the reconstruction at NOAA here (note: the earlier Briffa 2000 data here does contain a related series through to 1994.)
Above is a comparison showing the published tree ring data and the tree ring data that was deleted from the UNIPCC report and the NOAA archive.
On the graph, the black is the tree ring temperature data that was published by the UNIPCC and given to the NOAA archive by the CRU scientists. The red portion of the graph-- the tree ring temperature data since mid-20th century that did not suport the warming hypothesis-- was deleted from the UN report and the NOAA archive. The 'processed' ground station data (not shown) was put in its place, and of course the ground station data, when melded to the older tree ring data, gave the appearance of unprecidented warming. The raw ground station data, as I noted above, no longer exists, as it was discarded by the CRU scientists in the 1980's. It can't be checked.
So here's "Mike's Nature trick...to hide the decline":
The warmists switched the source of the data at the end of the graph, just at the point where the data contradicted their hypothesis, and replaced it with manipulated different-source data that supported their hypothesis. They deleted the original contradictory data from the published report and from the public database. When pressed by years of Freedom of Information Act requests to release the original raw 'supportive' data, they finally admit that they threw it out and it can never be checked.
Not just bad science. Fraud.