"There is still much that needs to be undertaken to reduce uncertainties, not just for the future, but for the instrumental (and especially the palaeoclimatic) past as well," Phil Jones, the former head of Britain's Climatic Research Unit told the BBC.
In a lengthy Q&A published at BBC.com Saturday, Jones also said: the recent warming trend that began in 1975 is not at all different than two other planetary warming phases since 1850; there has been no statistically significant warming since 1995, and; it is possible the Medieval Warm Period was indeed a global phenomenon thereby making the temperatures seen in the latter part of the 20th century by no means unprecedented.
Maybe most important, Jones explained what "hide the decline" in ClimateGate e-mail messages meant confirming they manipulated data (questions in bold, h/t Sonic Frog via Glenn Reynolds):
A - Do you agree that according to the global temperature record used by the IPCC, the rates of global warming from 1860-1880, 1910-1940 and 1975-1998 were identical? [...]
[T]he warming rates for all 4 periods are similar and not statistically significantly different from each other. [...]
B - Do you agree that from 1995 to the present there has been no statistically-significant global warming
Yes, but only just. [...]
G - There is a debate over whether the Medieval Warm Period (MWP) was global or not. If it were to be conclusively shown that it was a global phenomenon, would you accept that this would undermine the premise that mean surface atmospheric temperatures during the latter part of the 20th Century were unprecedented?
There is much debate over whether the Medieval Warm Period was global in extent or not. The MWP is most clearly expressed in parts of North America, the North Atlantic and Europe and parts of Asia. For it to be global in extent the MWP would need to be seen clearly in more records from the tropical regions and the Southern Hemisphere. There are very few palaeoclimatic records for these latter two regions.
Of course, if the MWP was shown to be global in extent and as warm or warmer than today (based on an equivalent coverage over the NH and SH) then obviously the late-20th century warmth would not be unprecedented. On the other hand, if the MWP was global, but was less warm that today, then current warmth would be unprecedented.
We know from the instrumental temperature record that the two hemispheres do not always follow one another. We cannot, therefore, make the assumption that temperatures in the global average will be similar to those in the northern hemisphere.
Now comes the part of the Q&A many will find most interesting:
K - How much faith do you have - and should we have - in the Yamal tree ring data from Siberia? Should we trust the science behind the palaeoclimate record?
First, we would all accept that palaeoclimatic data are considerably less certain than the instrumental data. However, we must use what data are available in order to look at the last 1,000 years.
I believe that our current interpretation of the Yamal tree-ring data in Siberia is sound. Yamal is just one series that enters some of the millennial long reconstructions that are available.
The current interpretation of the tree-ring data is "sound." Yet, Jones earlier said (emphasis added), "There is still much that needs to be undertaken to reduce uncertainties, not just for the future, but for the instrumental (and especially the palaeoclimatic) past as well."
Q - Let's talk about the e-mails now: In the e-mails you refer to a "trick" which your critics say suggests you conspired to trick the public? You also mentioned "hiding the decline" (in temperatures). Why did you say these things?
This remark has nothing to do with any "decline" in observed instrumental temperatures. The remark referred to a well-known observation, in a particular set of tree-ring data, that I had used in a figure to represent large-scale summer temperature changes over the last 600 years.
The phrase 'hide the decline' was shorthand for providing a composite representation of long-term temperature changes made up of recent instrumental data and earlier tree-ring based evidence, where it was absolutely necessary to remove the incorrect impression given by the tree rings that temperatures between about 1960 and 1999 (when the email was written) were not rising, as our instrumental data clearly showed they were.
This "divergence" is well known in the tree-ring literature and "trick" did not refer to any intention to deceive - but rather "a convenient way of achieving something", in this case joining the earlier valid part of the tree-ring record with the recent, more reliable instrumental record.
I was justified in curtailing the tree-ring reconstruction in the mid-20th Century because these particular data were not valid after that time - an issue which was later directly discussed in the 2007 IPCC AR4 Report.
This is important, for most people still don't understand what the decline they were trying to hide was.
As Marc Sheppard wrote in December, "[T]he decline Jones so urgently sought to hide was not one of measured temperatures at all, but rather figures infinitely more important to climate alarmists -- those determined by proxy reconstructions." He continued:
Jones was working on a cover chart for a forthcoming World Meteorological Organization report [PDF], "WMO Statement on the Status of the Global Climate in 1990," when he wrote the e-mail. As the graph would incorporate one reconstruction of his own plus one each from Michael Mann and Keith Briffa, Jones was informing them that he had used the trick on Mann's series at the same 1980 cutoff as MBH98, but found it necessary to use 1960 as the cutoff on the Briffa series.
Now, Jones has admitted this to the BBC: "[It] was absolutely necessary to remove the incorrect impression given by the tree rings that temperatures between about 1960 and 1999 (when the email was written) were not rising, as our instrumental data clearly showed they were."
In simple terms, Briffa's tree-ring data showed a decline in temperatures between 1960 and 1999 that weather stations around the world disagreed with. So, Jones spliced into Briffa's data set the real "instrumental" numbers for that period thereby hiding the decline.
This should raise eyebrows for a number of reasons. First, Jones and Company gave no notification to folks receiving this data -- including the Intergovernmental Panel and Climate Change -- that Briffa's numbers included instrumental data.
But more importantly, as the tree-ring numbers deviated so demonstrably from the observed temperature data between 1960 and 1999, why should anyone believe they're accurate for any periods in the past that can't be confirmed with instrumentation?
The entire global warming myth depends on tree-ring data that was grossly errant for forty years in the last century. This makes the decline ClimateGate scientists were trying to hide FAR MORE serious than most people believe.
Moving backward in the Q&A, there was another issue addressed by the BBC readers will find interesting:
N - When scientists say "the debate on climate change is over", what exactly do they mean - and what don't they mean?
It would be supposition on my behalf to know whether all scientists who say the debate is over are saying that for the same reason. I don't believe the vast majority of climate scientists think this. This is not my view. There is still much that needs to be undertaken to reduce uncertainties, not just for the future, but for the instrumental (and especially the palaeoclimatic) past as well.
So, the scientist at the heart of the ClimateGate scandal doesn't think the debate is over.
Given what he's now confirmed about significant flaws in the tree-ring data, the only thing surprising is that he'd admit it.
Are you listening Mr. Gore?
