Phil Jones momentous Q&A with BBC reopens the “science is settled” issues

14-02-2010

Professor Phil Jones unwittingly(?) reveals that the global warming emperor is, if not naked, scantily clad, vindicating key skeptic arguments

Annotated Version of the Phil & Roger Show – Guest post by Indur M. Goklany


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Readers of WUWT are already familiar with the remarkable series of questions and answers between the BBC’s Roger Harrabin at right, and Professor Phil Jones at left (see the posts by Willis and Anthony). [In case you don’t already know, Phil Jones is the climate scientist at the center of the Climategate e-mails, and whose compilation of historic global temperature data from the late 1800s to the present is a key element of the IPCC’s reports.] These Q-and-As, as readers of the two earlier posts recognize, reveal (a) the lack of empirical support for claims that recent warming is exceptional and (b) the flawed logic behind assertions that “Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.”

Specifically, the Q-and-As confirm what many skeptics have long suspected:

Neither the rate nor magnitude of recent warming is exceptional.
There was no significant warming from 1998-2009. According to the IPCC we should have seen a global temperature increase of at least 0.2°C per decade.
The IPCC models may have overestimated the climate sensitivity for greenhouse gases, underestimated natural variability, or both.
This also suggests that there is a systematic upward bias in the impacts estimates based on these models just from this factor alone.
The logic behind attribution of current warming to well-mixed man-made greenhouse gases is faulty.
The science is not settled, however unsettling that might be.
There is a tendency in the IPCC reports to leave out inconvenient findings, especially in the part(s) most likely to be read by policy makers.
In the following, I have annotated some of the more critical Qs-and-As. Note that the following version of the Q-and-A was “last updated at 16:05 GMT, Saturday, 13 February 2010”, and is a little different from the original that appeared on line. The questions, identified by A, B, C…,are in bold. I have added emphasis to PJ’s responses (also in bold). My comments are italicized and in bold within square brackets.

So that one can follow the thrust of my annotations, I should note that my general approach to problems or phenomena that human beings have observed in nature is that human observations — whether they span a few decades, a few centuries or even millennia — cover only a brief span in the existence of the earth. Thus, with regard to any observed change, where direct cause-and-effect cannot be verified, the null hypothesis should, in my opinion, be that the changes are due to natural variability. This is why it is important to figure out, among other things, whether the changes that have been observed are, as far as we know, likely to be within (or outside) the bounds of natural variability. If the current warming period (CWP) is not as warm as the medieval warming period (or the Roman and other Warming Periods), then it is impossible to make the argument that CWP is exceptional. Second, if earlier periods were warmer, this indicates natural variability is greater and it is harder to make the claim that we have a “stable” climate. Most importantly, if the earth and its species survived, if not thrived, despite these other warmer periods, then it becomes harder to make the argument that species cannot adapt or the end is nigh.

Excerpts from the Q-and-As, with annotations [in brackets], follow.

Q&A: Professor Phil Jones

… The BBC’s environment analyst Roger Harrabin put questions to Professor Jones, including several gathered from climate sceptics. The questions were put to Professor Jones with the co-operation of UEA’s press office.


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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?

An initial point to make is that in the responses to these questions I’ve assumed that when you talk about the global temperature record, you mean the record that combines the estimates from land regions with those from the marine regions of the world. CRU produces the land component, with the Met Office Hadley Centre producing the marine component.

Temperature data for the period 1860-1880 are more uncertain, because of sparser coverage, than for later periods in the 20th Century. The 1860-1880 period is also only 21 years in length. As for the two periods 1910-40 and 1975-1998 the warming rates are not statistically significantly different (see numbers below).

[This indicates that the recent warming is not exceptional. Moreover, even if it had been “exceptional,” that would not prove it is due to greenhouse gas emissions?]

I have also included the trend over the period 1975 to 2009, which has a very similar trend to the period 1975-1998.

[The fact that the magnitude of the trend for 1975-2009 is smaller than the trend for 1975-98 indicates that there has been no warming OR A DECLINE IN THE RATE OF WARMING from 1998-2009, which is not necessarily the same as saying there has been cooling during this period. HOWEVER, SEE KERR (2009), WHICH INDICATES NO WARMING FROM 1999-2008. Regardless, this is at odds with the IPCC’s model-based claim that were emissions frozen at 2000 levels then we would see a global temperature increase of 0.2°C per decade. This, in turn, suggests that the IPCC models have overestimated the climate sensitivity for greenhouse gases, underestimated natural variability, or both. This also suggests that there is a systematic upward bias in the impacts estimates based on these models. See here.]

So, in answer to the question, the warming rates for all 4 periods are similar and not statistically significantly different from each other. [This indicates that the recent warming is not exceptional. Moreover, even if it had been “exceptional,” that would not prove it is due to greenhouse gas emissions?]

Here are the trends and significances for each period:

Period Length Trend
(Degrees C per decade) Significance
1860-1880 21 0.163 Yes
1910-1940 31 0.15 Yes
1975-1998 24 0.166 Yes
1975-2009 35 0.161 Yes

…

D – Do you agree that natural influences could have contributed significantly to the global warming observed from 1975-1998, and, if so, please could you specify each natural influence and express its radiative forcing over the period in Watts per square metre.

This area is slightly outside my area of expertise. When considering changes over this period we need to consider all possible factors (so human and natural influences as well as natural internal variability of the climate system). Natural influences (from volcanoes and the Sun) over this period could have contributed to the change over this period. Volcanic influences from the two large eruptions (El Chichon in 1982 and Pinatubo in 1991) would exert a negative influence. Solar influence was about flat over this period. Combining only these two natural influences, therefore, we might have expected some cooling over this period. [Not necessarily — what about “natural internal variability” as well as other sources of “natural influences”? This response also assumes that we know all the modes and magnitudes of internal variability and pathways—both qualitatively and quantitatively—by which the sun, for instance, affects our climate.]

E – How confident are you that warming has taken place and that humans are mainly responsible?

I’m 100% confident that the climate has warmed. As to the second question, I would go along with IPCC Chapter 9 – there’s evidence that most of the warming since the 1950s is due to human activity.

[However, the key question — unfortunately unasked -- is what fraction of the warming is due not to human activity but to well-mixed man-made greenhouse gas emissions (such as CO2, CH4, and so forth but not including land use, land cover, soot, etc.). This is the key question only because the majority of the policy discussion is centered on reducing well-mixed greenhouse gases.]

…

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.

H – If you agree that there were similar periods of warming since 1850 to the current period, and that the MWP is under debate, what factors convince you that recent warming has been largely man-made?

The fact that we can’t explain the warming from the 1950s by solar and volcanic forcing – see my answer to your question D.

[1. Notably, Phil Jones doesn’t dispute the premise that “the MWP is under debate.” See Harrabin’s accompanying report. 2. The response is based on laughable logic. It is an “argument from ignorance”! See comments on answer to D. What about internal natural variability and other “natural influences”? How well do we know the external and internal sources of natural variability?]

…

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. …

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. [1. Given the divergence problem, how can it be assumed that tree rings are valid proxies for temperature for other places at other times? 2. The divergence problem may be well known among tree ring researchers but laymen and policy makers for whom the IPCC Summary for Policy Makers was supposedly written are generally ignorant of it. I also suspect that scientists in other disciplines were not aware of the divergence problem. They were owed this information up front, in the only document on climate change they were likely to read. Another sin of omission.]

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.

The misinterpretation of the remark stems from its being quoted out of context. The 1999 WMO report wanted just the three curves, without the split between the proxy part of the reconstruction and the last few years of instrumental data that brought the series up to the end of 1999. Only one of the three curves was based solely on tree-ring data.

The e-mail was sent to a few colleagues pointing out their data was being used in the WMO Annual Statement in 1999. I was pointing out to them how the lines were physically drawn. This e-mail was not written for a general audience. If it had been I would have explained what I had done in much more detail. ….