Memorandum submitted by Professor Ross
McKitrick (CRU 31)
SECTION 1: INTRODUCTION
1. I hold a Ph.D. in economics from the
University of British Columbia and I am a tenured full professor
of economics at the University of Guelph in Ontario, Canada. My
area of specialization is environmental economics, and I have
published many peer-reviewed papers in social and physical science
journals on the topic of climate change. Some of my research work
examines the quality of surface temperature data supplied by the
CRU to the Intergovernmental Panel on Climate Change (IPCC) for
its assessment reports. I have published several peer-reviewed
journal articles presenting statistical evidence that the CRU
climate data (CRUTEM) are not free of biases due to urbanization,
land use change and related socioeconomic processes.
2. In this memorandum I make the following
submissions for your consideration. (a) In my view the CRU makes
claims about the quality of its surface temperature data that
cannot be verified based on the documentation on its web site.
Nor is it possible from the publicly disclosed information to
determine exactly what input data is used for the production of
CRU climate data series and the extent to which it overlaps with
other data products. (b) Published studies have specifically tested
for and rejected claims that the CRU data products are adequately
filtered for climatic measurement purposes. This is an active
controversy in the scientific literature. (c) Professor Phil Jones,
along with his coauthor Kevin Trenberth of the US National Center
for Atmospheric Research, appears to me to have used his standing
as a Coordinating Lead Author of the IPCC Report to prevent evidence
calling into question CRU data used in the IPCC Report from being
shown to IPCC expert reviewers. (d) After the close of the review
process, misleading information was inserted into the text of
the IPCC Report which had the effect of downplaying evidence against
the quality of the data referred to in (c) above. It is my understanding
that Professor Jones had responsibility for the section in question.
3. With regard to your three questions,
I comment as follows.
3.1 The timing and content of the emails shows
that Jones was aware of a study that questioned the quality of
CRU data prior to the preparation of the first IPCC draft.
3.2 In addition to its existing terms of reference
the Independent Inquiry should consider whether CRU scientists
whose responsibilities include providing climate data to the IPCC
should not serve as IPCC Lead Authors (or Coordinating Lead Authors)
on any Report or Chapter that assesses evidence for or against
its quality for climatic research purposes.
3.3 The information needed to determine the independence
of CRU data products compared to other major surface temperature
series is not apparently available on the CRU web site, but it
can be surmised that the input data are not fully independent
across different products.
SECTION 2: QUESTIONS
ABOUT CRU DATA
4. The CRU publishes several versions of
a data set purporting to show trends in climatic temperatures
over land in 5x5 degree land-surface grid cells. I am concerned
herein with controversies surrounding the post-1979 interval.
Climatic data are not simply temperature records. It has been
known for many decades that temperatures at land-based observational
sites can be affected by changes in the land surface due to local
deforestation, introduction of agriculture, road-building, urbanization,
changes in monitoring equipment, measurement discontinuities,
and so forth; as well as by local emissions of particulates and
other air pollutants. These are considered non-climatic
influences, since they cause purely local, and in principle reversible,
changes in regional temperatures. Hence they must be filtered
out of the local temperature record in order to reveal the climatic
record. An ideal measurement of surface climatic changes would
require a monitoring site untouched by human development, the
equipment for which was consistent and perfectly maintained over
the entire measurement interval. However the actual data used
to produce climate data sets almost never satisfies these ideals.
Consequently, data sets published as "climate" records
are not simply observations: they are the outputs of models that
take weather records as inputs, apply adjustments aimed at removing
non-climatic influences, group the resulting records into regional
grids and then translate the data into deviations from a local
averages, yielding what are called gridded climate "anomalies".
5. The problems with raw temperature data
are widely recognized, including by the CRU. The CRU web page
(http://www.cru.uea.ac.uk/cru/data/hrg/) references data compilations
called CRU TS 1.x, 2.x and 3.x which are not subject to adjustments
for non-climatic influences. Users are explicitly cautioned not
to use the TS data for measuring or analyzing climate change in
the way apparently done in IPCC reports. The 1.2 release
of this product provided a list of FAQ's related to time series
analysis (see http://www.cru.uea.ac.uk/cru/data/hrg/timm/grid/ts-advice.html).
The first question, and its answer, are reproduced (in part) below.
Q1. Is it legitimate to use CRU TS 2.0 to
"detect anthropogenic climate change" (IPCC language)?
A1. No. CRU TS 2.0 is specifically
not designed for climate change detection or attribution
in the classic IPCC sense. The classic IPCC detection issue deals
with the distinctly anthropogenic climate changes we are already
experiencing. Therefore it is necessary, for IPCC detection to
work, to remove all influences of urban development or land use
change on the station data
.If you want to examine the detection
of anthropogenic climate change, we recommend that you use the
Jones temperature data-set. This is on a coarser (5 degree)
grid, but it is optimised for the reliable detection of anthropogenic
6. The implication is that the Jones data
has been adjusted "for the reliable detection of anthropogenic
trends." Readers are referred to some academic papers for
further explanation. The first is Brohan et al. (2005). This paper
does not explain how the data are adjusted, instead it focuses
on defending the claim that the potential biases are very small.
Two references are cited in support of this point. One is by US
scientist Thomas Peterson, which refers to the contiguous US only.
Another is by David Parker of the Hadley Centre, whose argument
relied on an apparent similarity between trends on windy and calm
nights. No references to papers critical of Parker's methods are
cited. Section 2.3.3 of Brohan et al. states that to properly
adjust the data would require a global comparison of urban versus
rural records, but classifying records in this way is not possible
since "no such complete meta-data are available" (p.
11), so the authors instead impose the assumption that the bias
is no larger than 0.006 degrees per century. This assumption
later appears in the 2007 IPCC Summary for Policymakers as
a research finding (see paragraph 18 below).
7. Brohan et al. refer to a 2003 paper
in Journal of Climate by Jones and Moberg, explaining the
CRUTEM version 2 data product. This paper also has little
information about the data adjustments. Reference is made to combining
multiple site records into a single series, but not to removing
non-climatic contamination. Moreover, the article points out (page
208) that it is difficult to say what homogeneity adjustments
have been applied since the original data sources do not always
include this information.
8. The other reference on the website is
to a 1999 Reviews of Geophysics paper by Jones, New,
Parker et. al. This paper emphasizes that non-climatic influences
(therein referred to as "inhomogeneities") must be corrected
(Section 2, p. 37) for the data to be useful for climatic research.
The part of the paper that provides information on the adjustments
is Section 2.1, consisting of only 3 paragraphs, none of
which explains the CRU procedures. The only explanatory statement
is (page 174):
"All 2000+ station time series used have
been assessed for homogeneity by subjective interstation comparisons
performed on a local basis. Many stations were adjusted and some
omitted because of anomalous warming trends and/or numerous nonclimatic
jumps (complete details are given by Jones et al. [1985, 1986c])."
9. Jones et al. [1985, 1986c] are technical
reports that were submitted to the US Department of Energy, but
they only cover data sets ending in the early 1980s, whereas the
data under dispute herein is the post-1979 interval. Even
if the adjustments were adequate in the pre-1980 interval
it is likely impossible to have estimated appropriate empirical
adjustments in the early 1980s for changes in socioeconomic patterns
that did not occur until the 1990s.
10. In sum, the CRU cautions that unadjusted
temperature data is inappropriate for the IPCC's purpose, and
for detection and attribution analysis more generally. The CRU
refers users instead to the CRUTEM products. Yet the accompanying
documentation does not appear to explain the adjustments made
to make the data products reliable for such usage.
11. These references also provide tables
of sources for the CRUTEM input data. It can be inferred from
the tables that a substantial portion of the raw data are from
the Global Historical Climatology Network (GHCN) maintained by
NOAA. These data are also used as inputs for the NASA and NOAA
global temperature series. Hence the three global climate data
series are not entirely independent. However the extent of overlap
cannot be determined without knowing exactly which GHCN series
are used for the CRU data set, which was one of the points subject
to Freedom of Information requests in 2009. In addition, without
provision of the non-GHCN source data, and a clear description
of the adjustments applied to all input data, it is likely impossible
to determine the overall independence between the CRU, GISS and
11. I have spent several years implementing
statistical models to test the claim that the adjustments to CRU
data are adequate. I have argued that an indication of inadequate
adjustments would be a significant correlation between the spatial
pattern of warming trends in climate data and the spatial pattern
of industrialization/socioeconomic development. My 2004 paper
in Climate Research, coauthored with Patrick J. Michaels,
showed that such correlations are large and statistically significant,
implying that the adjustments are likely inadequate. Our follow-up
paper in the Journal of Geophysical Research in 2007 re-established
these results on a new and larger global data base. Meanwhile
in 2004 and 2006 a team of Dutch meteorologists (de
Laat and Maurellis) also published research showing that gridded
climate data sets appear to be contaminated by effects of industrialization.
They used different methodologies, and we worked independently.
SECTION 3: THE
JONES 2004 EMAIL
12. CRU Email 1089318616.txt is available
at http://www.eastangliaemails.com/emails.php ?eid=419 &filename=1089318616.txt.
It appears to be a concatenation of two emails from Jones to Michael
Mann with the second one dated July 8 2004. I reproduce the
second one with the statement of interest underlined. The reference
to the "MM" paper is to my 2004 Climate Research
paper coauthored with Michaels.
From: Phil Jones <email@example.com>
To: "Michael E. Mann" <firstname.lastname@example.org>
Subject: HIGHLY CONFIDENTIAL
Date: Thu Jul 8 16:30:16 2004
Only have it in the pdf form. FYI ONLYdon't
pass on. Relevant paras are the last 2 in section 4 on
p13. As I said it is worded carefully due to Adrian knowing Eugenia
for years. He knows they're wrong, but he succumbed to her almost
pleading with him to tone it down as it might affect her proposals
in the future !
I didn't say any of this, so be careful how you
use itif at all. Keep quiet also that you have the pdf.
The attachment is a very good paperI've
been pushing Adrian over the last weeks to get it submitted to
JGR or J. Climate. The main results are great for CRU and also
for ERA-40. The basic message is clearyou have to put enough
surface and sonde obs into a model to produce Reanalyses. The
jumps when the data input change stand out so clearly. NCEP does
many odd things also around sea ice and over snow and ice.
The other paper by MM is just garbageas
you knew. De Freitas again. Pielke is also losing all credibility
as well by replying to the mad Finn as wellfrequently as
I see it.
I can't see either of these papers being in the
next IPCC report. Kevin and I will keep them out somehoweven
if we have to redefine what the peer-review literature is!
Climatic Research Unit Telephone
School of Environmental Sciences Fax
University of East Anglia
Norwich Email email@example.com
In a UK Guardian article of February 2, 2010,
Trenberth wholly disavows the underlined statement (http://www.guardian.co.uk/environment/2010/feb/02/hacked-climate-emails-flaws-peer-review).
13. The IPCC released the First Order Draft
in August 2005. Since this was over a year after Jones' email
to Mann it is clear he was aware of my study (it is not clear
what is the second paper to which he refers, but it might have
been one by de Laat and Maurellis, and I assume that it was).
The relevant section of the IPCC Draft was Chapter 3, pages 3-9 to
3-10. Consistent with the intent expressed in the email there
was no mention of either MM2004 or the de Laat and Maurellis
work. IPCC Expert Reviewer Vincent Gray criticized the omission
My expert review comments also criticized the omission.
14. The IPCC Second Order Draft was released
in March 2006. Again consistent with the intent revealed in Jones'
email to Mann, and despite reviewer demands, there was still no
mention of our findings or those of deLaat and Maurellis. I provided
lengthy feedback objecting to this omission. In June 2006 the
expert review period closed.
15. The final, published IPCC report in
May 2007 included a new paragraph that had not been included
in either of the drafts shown to reviewers. I surmise that Professor
Jones, as Coordinating Lead Author for Chapter 3, wrote the paragraph
alone or in consultation with Trenberth, and bears responsibility
for its inclusion in the published report.
McKitrick and Michaels (2004) and De Laat and
Maurellis (2006) attempted to demonstrate that geographical patterns
of warming trends over land are strongly correlated with geographical
patterns of industrial and socioeconomic development, implying
that urbanisation and related land surface changes have caused
much of the observed warming. However, the locations of greatest
socioeconomic development are also those that have been most warmed
by atmospheric circulation changes (Sections 220.127.116.11 and
3.6.4), which exhibit large-scale coherence. Hence, the correlation
of warming with industrial and socioeconomic development ceases
to be statistically significant. In addition, observed warming
has been, and transient greenhouse-induced warming is expected
to be, greater over land than over the oceans (Chapter 10), owing
to the smaller thermal capacity of the land.
(IPCC 2007 Chapter 3 page 244, emphasis
16. The concept of "statistical insignificance"
has a specific quantitative interpretation: it implies that an
empirical test has been done yielding a p value greater
than 0.1. The effects reported in MM2004 had p values
on the order of 0.002 or 0.2%, indicating significance. The
claim that our results were statistically insignificant is inaccurate
and was made without any supporting citation. To my knowledge
no study showing such a thing exists, and in fact I have a new
paper forthcoming in a peer-reviewed statistics journal (see http://sites.google.com/site/rossmckitrick)
countering the specific claim that accounting for atmospheric
circulation effects undermines our previously-published results.
17. The highlighted portion of the inserted
paragraph (see paragraph 15 above) is unsupported, and in
the context appears to reflect a fabricated conclusion. It was
not included in the drafts that underwent expert review. Moreover,
the references to sections 18.104.22.168 and 3.6.4 of the
IPCC Report are misleading since neither section presents evidence
that warming due to atmospheric circulation changes occurs in
the regions of greatest socioeconomic development. Neither section
even mentions industrialization, socioeconomic development, urbanization
or any related term. The final sentence in the quoted paragraph
is irrelevant to the present discussion since the debate only
concerns data over land: there is obviously no economic development
over the open ocean.
18. The CRU data was crucial for some of
the main conclusions in the published version of IPCC Report.
Global temperature trends are presented in Table 3.2 on page
243 of the IPCC Report. The accompanying text (page 242)
states that the CRU data uncertainties "take into account"
biases due to urbanization. The Executive Summary to the chapter
(page 237) asserts that "Urban heat island effects are real
but local, and have not biased the large-scale trends
very real but local effects are avoided or accounted for in the
data sets used." The influential Summary for Policymakers
"Urban heat island effects are real but
local, and have a negligible influence (less than 0.006°C
per decade over land and zero over the oceans) on these values."
The supporting citation was to Section 3.2,
which relied on apparently unsubstantiated material. IPCC Chapter
9 provides the summary of evidence attributing warming to
greenhouse gases. The problem of CRU surface data contamination
is set aside as follows (p. 693):
Systematic instrumental errors, such as changes
in measurement practices or urbanisation, could be more important,
especially earlier in the record (Chapter 3), although these errors
are calculated to be relatively small at large spatial scales.
Urbanisation effects appear to have negligible effects on continental
and hemispheric average temperatures (Chapter 3).
Again, the rationale for ignoring the issue
of CRU data quality problems relies on a citation to Chapter 3,
which in turn relied upon apparently unsubstantiated evidence.
19. I submit that sufficient evidence to
disprove a claim of evidence fabrication would consist of the
p value supporting the claim of statistical insignificance,
the peer-reviewed journal article in which it was presented, and
the page number where the study is cited in the IPCC Report. An
inability to produce these things would, I submit, have relevance
for answering the first Inquiry question.
Professor Ross McKitrick
Department of Economics
University of Guelph, Canada