the final editing of one of the chapters of the SAR, a new procedure was
introduced for the TAR. Two Review Editors were appointed for each of the
chapters, one being a member of the WGI Bureau and the other an independent
scientist who was not otherwise involved in the chapter preparation. The role of
the Review Editors was to watch over the reviewing of the expert and government
comments and to certify that all the comments were appropriately considered
and responded to by the Lead Authors. A particular responsibility was to ensure
that genuine differences of view among experts were adequately reflected in the
revised text. The Lead Authors have welcomed the presence and assistance of the
Review Editors and recognized their role in enhancing the credibility of the
process and in protecting the Lead Authors from inappropriate or unfounded
criticism.
For the drafting of the Technical Summary (TS) a team of Lead Authors with
strong representation from the chapters was set up by the WGI Bureau; four
members of the Bureau also agreed to act as Review Editors for the TS. A draft of
the TS was agreed at the Auckland meeting in February 2000 and sent out for
government and expert review along with the chapters. For the Summary for
Policymakers (SPM), the Bureau set up a drafting team of about 60, consisting of
all the Bureau members, a good representation of Lead Authors and a few others
with experience of industry and policy or to ensure adequate geographical
representation. A draft of the SPM was also produced at the Auckland meeting
and sent out to governments and experts for review.
Following detailed review of both the TS and the SPM at the Victoria Lead
Authors’ meeting in July 2000, a special meeting of the TS Lead Authors and the
SPM writing team was held in New York in October 2000 to rewrite both
documents in the light of the final drafts of the chapters as revised at and
subsequent to the Victoria meeting. The revised chapters, TS and SPM were then
sent to governments in October 2000 in preparation for the Plenary meeting of
WGI held in January 2001.
A new feature in the TAR compared with previous reports is the treatment of
uncertainty. During the preparation of the TAR a great deal of thought was given
to the quantification of uncertainty. In some cases, data are available that enable
probabilities of certainty to be estimated by well defined statistical procedures. In
other cases scientific judgement plays a large part in the estimation of
uncertainty. In either case, what is most helpful to policymakers is that words
used to describe levels of uncertainty are employed in a consistent and, so far as is
possible, a quantified manner. In the SPM and the TS of WGI therefore, words
defined as follows were used where appropriate to indicate estimates of
confidence: virtually certain (greater than 99% chance that a result is true); very
likely (90—99% chance); likely (66—90% chance); medium likelihood (33—66%
chance); unlikely (10—33% chance); very unlikely (1—10% chance); exceptionally
unlikely (:1% chance). Slightly different definitions were employed by WGII.*
The purpose of the WGI Plenary meeting held in Shanghai in January 2001
was to debate the SPM and agree its wording in detail. The meeting had to be
satisfied that the SPM presented comprehensive, accurate and balanced science
* WGII used: very high (95% or greater), high (67—95%), medium (33—67%), low (5—33%) and very low
(5% or less).
An Overview of the Intergovernmental Panel on Climate Change
13
introduced for the TAR. Two Review Editors were appointed for each of the
chapters, one being a member of the WGI Bureau and the other an independent
scientist who was not otherwise involved in the chapter preparation. The role of
the Review Editors was to watch over the reviewing of the expert and government
comments and to certify that all the comments were appropriately considered
and responded to by the Lead Authors. A particular responsibility was to ensure
that genuine differences of view among experts were adequately reflected in the
revised text. The Lead Authors have welcomed the presence and assistance of the
Review Editors and recognized their role in enhancing the credibility of the
process and in protecting the Lead Authors from inappropriate or unfounded
criticism.
For the drafting of the Technical Summary (TS) a team of Lead Authors with
strong representation from the chapters was set up by the WGI Bureau; four
members of the Bureau also agreed to act as Review Editors for the TS. A draft of
the TS was agreed at the Auckland meeting in February 2000 and sent out for
government and expert review along with the chapters. For the Summary for
Policymakers (SPM), the Bureau set up a drafting team of about 60, consisting of
all the Bureau members, a good representation of Lead Authors and a few others
with experience of industry and policy or to ensure adequate geographical
representation. A draft of the SPM was also produced at the Auckland meeting
and sent out to governments and experts for review.
Following detailed review of both the TS and the SPM at the Victoria Lead
Authors’ meeting in July 2000, a special meeting of the TS Lead Authors and the
SPM writing team was held in New York in October 2000 to rewrite both
documents in the light of the final drafts of the chapters as revised at and
subsequent to the Victoria meeting. The revised chapters, TS and SPM were then
sent to governments in October 2000 in preparation for the Plenary meeting of
WGI held in January 2001.
A new feature in the TAR compared with previous reports is the treatment of
uncertainty. During the preparation of the TAR a great deal of thought was given
to the quantification of uncertainty. In some cases, data are available that enable
probabilities of certainty to be estimated by well defined statistical procedures. In
other cases scientific judgement plays a large part in the estimation of
uncertainty. In either case, what is most helpful to policymakers is that words
used to describe levels of uncertainty are employed in a consistent and, so far as is
possible, a quantified manner. In the SPM and the TS of WGI therefore, words
defined as follows were used where appropriate to indicate estimates of
confidence: virtually certain (greater than 99% chance that a result is true); very
likely (90—99% chance); likely (66—90% chance); medium likelihood (33—66%
chance); unlikely (10—33% chance); very unlikely (1—10% chance); exceptionally
unlikely (:1% chance). Slightly different definitions were employed by WGII.*
The purpose of the WGI Plenary meeting held in Shanghai in January 2001
was to debate the SPM and agree its wording in detail. The meeting had to be
satisfied that the SPM presented comprehensive, accurate and balanced science
* WGII used: very high (95% or greater), high (67—95%), medium (33—67%), low (5—33%) and very low
(5% or less).
An Overview of the Intergovernmental Panel on Climate Change
13