I love how these things take on a life of their own. The "deletion of the data" here refers to tree-ring data that were suggesting a decline in temperatures, which conflicted with the warming shown by records from thousands of weather stations around the world. So it depends on whether you think tree-rings are more accurate than thermometers in terms of their ability to record temperature.caedmon wrote:But given the deletion of the data that showed (by CRU's own admission) a cooling trend since 1960...I am curious as to WHAT data this reporting is based on.
I can see it now: A guy asks his wife, a global warming skeptic, "Honey, what's the temperature outside?" She responds, "Hang on, let me just get the chain saw and I'll tell you in a couple of minutes."
Here's an excerpt from the current Wikipedia entry on the CRU emails:
An excerpt from one November 1999 e-mail authored by Phil Jones, which the UEA has stated refers to a graph he was preparing as a diagram for the cover of the World Meteorological Organization (WMO) statement on the status of global climate in 1999:[25]
"I've just completed Mike's Nature trick of adding in the real temps to each series for the last 20 years (ie, from 1981 onwards) and from 1961 for Keith's to hide the decline."[1][26][27]
The graph showed three series of paleoclimate reconstructions, based on records of tree rings, corals, ice cores, lake sediments, etc., along with historical and instrumental records.[28][29] "Mike's Nature trick" referred to a paper published by Michael Mann in Nature in 1998, which combined various proxy records with actual temperature records. Mann described the "trick" as simply a concise way of showing the two kinds of data together while still clearly indicating which was which. He said that there was nothing "hidden or inappropriate" about it, and that his method of combining proxy data had been corroborated by numerous statistical tests and matched thermometer readings taken over the past 150 years.[18] A press release by the University of East Anglia said that the "trick" was using instrumental data to meet a requirement of showing temperatures more recent than those covered by the proxy based temperature reconstructions, and that the use of the word "trick" was not intended to imply any deception.[29]
The phrase "hide the decline" referred specifically to the divergence problem in which post 1960 tree ring proxy data indicate a decline while measured temperatures rise. The reconstruction by Keith Briffa et al. was based solely on tree ring data, which shows a strong correlation with temperature from the 19th century to the mid 20th century.[29] They had published a statement on the divergence problem in 1998, and had recommended that the post 1960 part of their reconstruction should not be used.[30] Jones stated that the email was "written in haste" and that, far from seeking to hide the decline, CRU had published a number of articles on the problem. The implications of the decline are discussed in Chapter 6 of the 2007 IPCC Fourth Assessment Report,[29] which describes discussion of various possible reasons for the divergence which does not affect all the trees, and says that there is no consensus about the cause. It notes that Briffa et al. specifically excluded the post 1960 data, which is therefore not shown in the graph of their reconstruction in the report.[31] In his review comments on the report, Stephen McIntyre objected to this graph being truncated, and said that the whole reconstruction should be shown with comments to deal with the "divergence problem". The IPCC response was that this would be inappropriate.[32]
Richard Lindzen of the Massachusetts Institute of Technology, who has in the past said that graphs were prepared dishonestly and expressed doubts about whether there should be serious concern about global warming, has gone on the record accusing Mann of data rigging and outright falsification. Other climatologists disputed Lindzen's comments. Thomas Peterson of the National Climatic Data Center said he had seen nothing in the emails that called the fundamental science into question, and Andrew Solow of Woods Hole Oceanographic Institution agreed that there was no trickery, saying he would use the word trick to describe some methodological step, but expressed the view that the basis of reconstructions had been unclear.[18] Several scientific sources state that the decline being referred to is a decline in tree ring climate proxy metrics, not temperature.[33][29][34] Andrew Watson, Royal Society Research Professor at the UEA, said that the scientists had drawn the line to follow the tree-ring reconstruction up to 1960 and the measured temperature after that."[35]
McIntyre said that the "trick to hide the decline" consisted of removing tree-ring data from the later half of the 20th century. He said that since the cause of the divergence problem is unknown, and it may have existed in earlier periods, tree ring records cannot be used to estimate temperatures in the past.[36]
Before the incident, continuing research had already presented reconstructions based on more proxies, and found similar results with or without the tree ring records.[37]
