P. N. Edwards and S. H. Schneider Self-Governance and Peer Review1
Chapter 7. Self-Governance and Peer Review in Science-for-
Policy: The Case of the IPCC Second Assessment Reporti
In Clark Miller and Paul N. Edwards, eds., Changing the Atmosphere: Expert
Knowledge and Environmental Governance (Cambridge, MA: MIT Press, 2001
Not for citation or circulation without permission.
by
Paul N. Edwards
Associate Professor
School of Information
University of Michigan
Stephen H. Schneider
Professor, Dept. of Biological Sciences
Senior Fellow, Institute for International Studies
Stanford University
In the spring of 1996, the Intergovernmental Panel on Climate Change (IPCC) released
its long-awaited Second Assessment Report (SAR) on possible human impacts on the
global climate system. The report’s eighth chapter concluded that “the balance of
evidence suggests that there is a discernible human influence on global climate”
(Houghton et al. 1996, 5) — a phrase that has since become probably the single most-
cited sentence in the IPCC’s history. The Global Climate Coalition (an energy industry
lobby group) and a number of “contrarian” scientists immediately launched a major,
organized attack designed to discredit the report’s conclusions, especially those relating
to the crucial question of whether human activities are responsible for changes in the
world’s climate.
Led by the eminent physicist Frederick Seitz, these critics claimed that the IPCC had
inappropriately altered a key chapter for political reasons. They alleged that the IPCC
had “corrupted the peer review process” and violated its own procedural rules. These
charges ignited a major debate, widely reported in the press, lasting several months.
The accusations of corruption reach a fundamental issue in the emerging global climate
regime: namely, how the IPCC as a self-governing institution can maintain scientific
integrity in the face of intense political pressures (both internal and external) and tightly
constrained deadlines. In this chapter we consider these charges on three levels. First,
we evaluate their accuracy as specific challenges to the IPCC peer review process, and
note how the IPCC rules of procedure might be clarified to avoid them in the future.
Second, we explore their meaning against the larger background of the IPCC’s role in
the politics of climate change. Finally, we use this episode to examine more fundamental
questions about the role of formal review mechanisms in certifying scientific knowledge
produced for policy contexts, and about the relative importance of those mechanisms in
different national and cultural contexts.

P. N. Edwards and S. H. Schneider Self-Governance and Peer Review2
The IPCC Second Assessment Report
The IPCC is an office of the United Nations Environment Programme and the World
Meteorological Organization. Its purpose is to evaluate and synthesize the scientific
understanding of global climate change for national governments and United Nations
agencies, as expert advice for use in the ongoing negotiations under the Framework
Convention on Climate Change (FCCC). The agency’s nominal goal is to represent fairly
the full range of credible scientific opinion. Where possible, it attempts to identify a
consensus view on the most likely scenario(s). When consensus cannot be reached, the
agency’s charge is to summarize the major viewpoints and the reasons for
disagreement. IPCC reports are intensively peer-reviewed. They are regarded by most
scientists and political leaders as the single most authoritative source of information on
climate change and its potential impacts on environment and society.
Like all IPCC assessments, the SAR contained three “Summaries for Policymakers”
(SPMs), one for each of the IPCC’s three Working Groups: climate science (Working
Group I), impacts of climate change (Working Group II), and economic and social
dimensions (Working Group III) (Bruce, Lee, and Haites 1996; Houghton et al. 1996;
Watson et al. 1996). Since the full SAR stretches to well over 2,000 pages — most of it
dense technical prose — few outside the scientific community are likely either to read it
in its entirety or to understand most of its details. Therefore, these summaries tend to
become the basis for press reports and public debate. For this reason, the Working
Groups consider their exact wording with extreme care before they are published. At the
end of the IPCC report process, they are approved word for word by national
government representatives at a plenary meeting attended by only a fraction of the lead
authors.
The SPM for Working Group I, which assesses the state of the art in the physical-
science understanding of climate change, contained the following paragraph:
Our ability to quantify the human influence on global climate is currently
limited because the expected signal is still emerging from the noise of
natural variability, and because there are uncertainties in key factors.
These include the magnitude and patterns of long–term natural variability
and the time–evolving pattern of forcing by, and response to, changes in
concentrations of greenhouse gases and aerosols, and land surface
changes. Nevertheless, the balance of evidence suggests that there is a
discernible human influence on global climate (Houghton et al. 1996, 5,
emphasis added).
Three-quarters of this paragraph consists of caveats about uncertainties and limitations
of current understanding. Nonetheless, its now-famous closing sentence marked the first
time the IPCC had reached a consensus on two key points: first, that global warming is
probably occurring (“detection”), and second, that human activity is more likely than not
a significant cause (“attribution”). Like this summary paragraph, the body of the report
discussed — frequently and at length — the large scientific uncertainties about
attribution. The Working Group carefully crafted the SPM’s “balance of evidence”
sentence to communicate the strong majority opinion that despite these uncertainties,
studies were beginning to converge on a definitive answer to the attribution question.