Dear Colleagues:
We have written an open letter (below) about the IPCC process, media attention,
errors, and suggestions for improvement, which we are circulating to both IPCC
authors and other scientists in the US. If you would like to be a co-signer of
the letter, please send your name and institutional affiliation to Gary Yohe at
[email protected] by close of business, Friday March 12.
We plan to send the letter to the State Department, EPA, NOAA, the Office of
Science and Technology Policy, the Council on the Environment and other
relevant US agencies and organizations.
Because it won't be possible to coordinate multiple versions, we do not plan to
edit this letter further at this juncture. However, if you do have comments,
please feel free to include them in your email response.
Please circulate the open letter to your colleagues if you would like. We
apologize for any cross-listings in advance.
Best,
Gary Yohe
Steve Schneider
Cynthia Rosenzweig
Bill Easterling
An Open Letter from Scientists in the United States on the Intergovernmental
Panel on Climate Change and Errors Contained in the Fourth Assessment Report:
Climate Change 2007
Many in the popular press and other media, as well as some in the halls
of Congress, are seizing on a few errors that have been found in the Fourth
Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC)
in an attempt to discredit the entire report. None of the handful of
mis-statements (out of hundreds and hundreds of unchallenged statements),
remotely undermines the conclusion that the planet is warming unequivocally and
that most of the observed increase in global average temperatures since the
mid-twentieth century is very likely due to observed increase in anthropogenic
greenhouse gas concentrations. Despite its excellent performance for accurately
reporting the state-of-the-science, we certainly acknowledge that the IPCC
should become even better, more forthcoming in openly acknowledging errors in a
timely fashion, and continuing to improve its assessment procedures to further
lower the already very low rate of error.
It is our intention in offering this open letter to bring the focus
back to credible science, rather than invented hyperbole, so that it can bear
on the policy debate in the United States and throughout the world. We first
discuss some of the key messages from climate science and then elaborate on
IPCC procedures, with particular attention on the quality-control mechanisms of
the IPCC. Finally we offer some suggestions about what might be done next to
improve IPCC practices and restore full trust in climate science.
The Climate Challenge
Our understanding of human contributions to climate change and the
associated urgency for humans to respond has improved dramatically over the
past two decades. Many of the major components of the climate system are now
well understood, though there are still some sources of significant uncertainty
(like the processes that produce the observed rapid ice-sheet melting and/or
collapse in the polar regions). It is now well established, for example, that
atmospheric concentrations of greenhouse gases from human sources have
increased rapidly since the Industrial Revolution. Increasing concentrations
of greenhouse gases in the atmosphere change the heat going into and out of the
climate system, i.e., the radiation balance of the earth - and so first
principles of physics tell us to expect, with a very high likelihood, that
higher temperatures should have been observed.
Indeed, measurements of global average temperatures show an increase of
about 0.6 degrees C over the past century and about 0.8 degrees C warming since
mid-19th century. The pattern of increase has not been smooth or monotonic.
There have been several 10- or 15-year periods of stable or declining
temperatures over the past 150 years, but 1998 was the warmest (or slightly in
second place) year in this period and 11 of the warmest years have been
experienced in the 12 years between 1995-2006. Since 1970, observational
evidence from all continents and most oceans shows that many natural systems
are already being affected by these temperature increases.
Because the long-term warming trends demonstrate extraordinarily high
statistical significance, the current decadal period of stable global mean
temperature does nothing to alter a fundamental conclusion from the AR4:
warming has unequivocally been observed and documented. Moreover,
well-understood lags in the responsiveness of the climate system to
disturbances like greenhouse gas increases mean that the current temperature
plateau will very likely not persist much longer. Global climate model
projections show that present-day greenhouse gas concentrations have already
committed the planet to more than another 1 degree C in warming over the coming
decades.
Increasing emissions of carbon dioxide from the consumption of coal,
oil and natural gas as well as deforestation have been the major drivers of
this observed warming. While we cannot predict the details of our climate
future with a high degree of certainty, the majority of studies from a large
number of research groups in the US and elsewhere project that unabated
emissions could produce between 1 and 6 degrees C more warming through the year
2100.
Other research has identified multiple reasons to be concerned about
climate change; these apply to the United States as well as globally. They
include (1) risks to unique and threatened systems (including human
communities), (2) risks from extreme events (like coastal storms, floods,
droughts, heat waves, and wildfires), (3) economic damages (driven by, for
example, pest infestations or inequities in the capacity to adapt), (4) risks
from large-scale abrupt climate change (e.g., ice-sheet collapse, ocean
circulation slowing, sharply increased methane emissions from permafrost) or
abrupt impacts of more predictable climate change (generated by thresholds in
the coping capacities of natural and human systems to climate variability), and
(5) risks to national security (driven largely by extreme events across the
world interacting with already-stressed situations).
These sources of risk and the potential for triggering
temperature-driven impacts at lower thresholds, as well as the explicit
recognition in the AR4 that risk is the product of likelihood and consequence,
led the nations of the world to take note of the Copenhagen Accord last
December. The Accord highlights 2 degrees C in warming above preindustrial
temperature levels as a target that might reduce the chance of "dangerous
anthropogenic interference with the climate system" to more manageable levels.
Research has shown that significantly increasing the likelihood of achieving
this goal over the next century is economically and technically feasible with
emission reduction measures and changes in consumption patterns; but it will
not be easy without major national and international actions to deviate
substantially from the status quo.
The IPCC and the Fourth Assessment Report
The World Meteorological Organization (WMO) and the United Nations
Environment Programme (UNEP) established the IPCC in 1988 to provide policy
makers regularly with balanced assessments of the state of knowledge on climate
change. In so doing, they created an open intergovernmental organization to
which policy analysts, engineers, resource managers and renowned scientists
from all over the world were asked to collaborate. At present, more than 150
countries including the United States participate in the IPCC. IPCC publishes
an assessment report approximately every six years. The most recent Fourth
Assessment, approved by member countries and released in 2007, contained three
volumes: The Physical Science Basis (Working Group I); Impacts, Adaptation and
Vulnerability (Working Group II) and Mitigation of Climate Change (Working
Group III) and a Synthesis Report. More than 44 writing teams and 450 lead
authors contributed to the Fourth Assessment - authors who hav!
e been selected on the basis of their expertise in consultation with all
member countries and who were assisted by another 800 scientists and analysts
who served as contributing authors on specific topics. Authors donated their
time gratis, and the entire process was supported by four Technical Support
Units (TSUs) that employ 5 to 10 people each.
Errors in the Fourth Assessment Report
It was hard not to notice the extraordinary commotion that erupted
around errors that were eventually found in the AR4. The wrong year for the
projected disappearance of the Himalayan glaciers and the wrong percentage of
'land below sea level' in the Netherlands are examples of errors that need to
be acknowledged frankly and rectified promptly. In a few other cases, like the
discussion of the correlations between crop yields, climate change, and climate
variability in North Africa, caveats that were carefully crafted within
chapters were not included when language was shortened for the Working Group II
Summary for Policymakers and the Synthesis Report. While striving to simplify
technical details and summarize major points, some important qualifications
were left behind. These errors of omission in the summary process should also
be recognized and corrected. Other claims, like the one reported at the end of
February suggesting that the AR4 did not mention the numbe!
r of people who will see increases in water availability that were reported in
the cited literature along with the millions of more people who will be at risk
of water shortage, are simply not true. In any case, it is essential to
emphasize that none of these interventions from outside the IPCC alter the key
finding from the AR4 that human beings are very likely changing the climate,
with far-reaching impacts in the long run.
The heated debates that have emerged around these instances have even
led some to question the quality and integrity of the IPCC. Recent events have
made it clear that the quality control procedures of the IPCC are not
watertight, but claims of widespread and deliberate manipulation of scientific
data and fundamental conclusions in the AR4 are not supported by the facts. We
also strongly contest the impression that the main conclusions of the report
are based on dubious sources. The reference list of the AR4 contains about
18,000 citations, the vast majority of which were published in peer-reviewed
scientific journals. The IPCC also has transparent procedures for using
published but not peer-reviewed sources in their reports. These procedures
were not properly followed in the isolated Himalaya case, but that statement
was never elevated into the Summary for Policymakers of either Working Group II
or the Synthesis Report - documents that were approved unanimously a!
nd word for word by all member nations.
Nonetheless, failsafe compliance with these procedures requires extra
attention in the writing of the next round of assessments. We propose
implementing a topic-based cross-chapter review process by which experts in an
impact area of climate change, such as changes in water resources, scrutinize
the assessment of related vulnerability, risk analyses, and adaptation
strategies that work downstream from such changes. Here we mean, to continue
the example, assessments of possible increases in flooding damage in river
basins and the potential for wetlands to provide buffers in the sectoral and
regional chapters. This would be most productively implemented just before the
first-order draft, so that chapter authors can be alerted to potential problems
before the major review step.
Quality Control within the IPCC and US Review
The impression that the IPCC does not have a proper quality-control
procedure is deeply mistaken. The procedure for compiling reports and assuring
its quality control are governed by well-documented principles that are
reviewed regularly and amended as appropriate. Even now, every step in the
preparation of every chapter can be traced on a website: First Order Drafts
(with comments by many scientists as well as author responses to those
comments), Second Order Drafts in which those comments are incorporated (and
comments by experts and country representatives on revised versions as well as
another round of author responses), and so on, up through the final,
plenary-approved versions.
To be clear, 2,500 reviewers together provided about 90,000 comments
on the 44 chapters for the AR4. Each comment is documented on a website that
also describes how and why the comment was or was not incorporated in the next
revision. Review editors for each chapter worked with the authors to guarantee
that each comment was treated properly and honestly in the revision; in fact,
no chapter can ever move forward for publication without the approval of its
set of two or three review editors.
The US Government opened its reviews of the draft IPCC report to any US
expert who wanted to review it. In order to protect against having this
preliminary pre-reviewed draft leaked before its ultimate approval by the IPCC
Plenary, the US Government asked all potential reviewers to agree not to
disclose the contents of the draft. For each report, the US Government
assembled its own independent panel of government experts to vet the comments
before submission to the IPCC. Anything with scientific merit was forwarded.
There were multiple rounds for each of the Working Group reports and the
Synthesis Report, and opportunities for US experts to review the drafts were
posted as Federal Register notices.
IPCC principles also govern how authors treat published but non-peer
reviewed sources. These procedures acknowledge that peer-reviewed scientific
journals contain little information about on-the-ground implementation of
adaptation or mitigation - matters such as the emission reduction potential in
a given industrial sector or country, for example, or catalogues of the
specific vulnerabilities and adaptation strategies of sectors and regions with
regard to climate change. This information is frequently only available in
reports from research institutes, reports of workshops and conferences, or in
publications from industries or other non-governmental organizations. This is
the so-called gray literature. The IPCC procedure prescribes that authors are
obliged critically to assess any gray source that they wish to include. The
quality and validity of a finding from a non-peer reviewed source needs to be
verified before its finding may be included in a chapter text. Ea!
ch source needs to be completely traceable; and in cases where gray sources
are used, a copy must be deposited at the IPCC Secretariat to guarantee that it
is available upon request for third parties.
We conclude that the IPCC procedures are transparent and thorough, even
though they are not infallible. Nonetheless, we are confident that no single
scholar or small group of scholars can manipulate the process to include or to
exclude a specific line of research; authors of that research can (and are
fully encouraged to) participate in the review process. Moreover, the work of
every scientist, regardless of whether it supports or rejects the premise of
human-induced climate change, is subject to inclusion in the reports. The work
is included or rejected for consideration based on its scientific merit.
It is important to note, at least in passing, that we are not
addressing here the criteria and procedures by which the IPCC selects chairs
and authors. These are handled exclusively by the IPCC and its members
according to terms of reference that were initially defined in the authorizing
language of 1988. That is to say, governments or their appointees frame and
implement these policies; and they create, approve and staff Technical Support
Units for each working group. We have no suggestions to offer on these topics
since they lie well beyond our purview.
What comes next?
The National Academies of Sciences will shortly release a series of
subsequent assessments under the America's Climate Choices rubric. We expect
that the robust findings of the AR4 will be supported by new information
gleaned from literature published since 2006, and that IPCC findings will be
confirmed - i.e., that the climate change issue is serious and urgent and
deserves the serious, urgent and non-partisan consideration of the country's
legislative and administrative leaders. In short, we feel strongly that
exaggerated focus on a few errors from 2007 cannot be allowed to detract from
open and honest deliberations about how to respond to climate risk by reducing
emissions and promoting adaptation at home and abroad.
As the process of producing the IPCC Fifth Assessment Report (AR5)
begins, the IPCC should become more responsive in acknowledging errors rapidly
and openly as they become known. To this end, we urge the IPCC to put an
erratum on its website that rectifies all errors that have been discovered in
the text after publication. In doing so, a clear distinction needs to be made
between errors and progressing knowledge. IPCC assessments are detailed
snapshots of the state of scientific knowledge at a given time, while knowledge
evolves continuously through ongoing research and experience; it is the errors
in the assessments that need immediate attention. In contrast, progressing
knowledge is published in new scientific journal articles and reports; this
information should be used as a basis for the AR5, but it cannot be listed as
errata for the AR4 because it was not available when that assessment was
conducted. The website should, as well, respond rapidly and openly wh!
en reports of errors in past assessments are themselves in error. We cannot
let misperceptions fester anymore than errors go uncorrected.
Climate research and the IPCC reports on the state of knowledge provide
a scientific foundation for climate policy making, whose agenda is defined by
the governments of the IPCC not the lead authors per se. The quality of and
the balance in the knowledge delivered by any assessment is certainly
essential, as is clear and explicit communication of associated uncertainties.
Given the recent political and media commotion surrounding a few clear errors,
it is now equally essential that we find ways to restore full trust in the
integrity of the overwhelming majority of the climate change research and
policy communities. To that end, we are pleased that an independent critical
evaluation of IPCC procedures will be conducted; we hope that the process will
solicit participation by the National Academies of the member nations.
The significance of IPCC errors has been greatly exaggerated by many
sensationalist accounts, but that is no reason to avoid implementing procedures
to make the assessment process even better. The public has a right to know the
risks of climate change as scientists currently understand them. We are
dedicated to working with our colleagues and government in furthering that task.
March 12, 2010
Signed:
Gary W. Yohe Wesleyan University
Stephen H. Schneider Stanford University
Cynthia Rosenzweig NASA Goddard Institute for Space Studies
William E. Easterling Pennsylvania State University
