changes in climate might be the result of anthropogenic change. The WGI
Plenary Meeting debated for a considerable time how to express this somewhat
greater scientific confidence in the interpretation of the recent climate record,
although still surrounded by much uncertainty. A sentence carefully crafted by
the meeting was unanimously agreed by the delegates: ‘the balance of evidence
suggests a discernible human influence on global climate’.
Following the 1995 Report, the IPCC produced several Technical Papers in
order to answer particular questions of importance to policymakers. Also several
Special Reports were written addressing particular issues. Of especial importance
was a report on Aviation and the Global Atmosphere carried out in cooperation
with the International Civil Aviation Organisation (ICAO); the authors of the
report included many from the aviation industry. The report addressed the
impact of emissions from aircraft engines on the atmosphere and the climate and
what could be done through engine design or through operational procedures to
minimize the impact. Of particular interest was the result that the influence of
aerosol (small particles) produced from the aircraft emissions together with
emissions of water vapour could have a significant effect on the cloud cover at
aircraft cruising altitudes, with an effect on climate possibly comparable to that of
the carbon dioxide emitted by aircraft.
8 Attacks on the IPCC
The IPCC and its work has been attacked from two fronts; on the one hand by
those who argue that the projections of global warming and its consequences
have been grossly overplayed and that there is no need for any action, and on the
other hand by those who believe that possible serious consequences of global
warming have been ignored and that there is urgent need for much more drastic
action. Both these points of view have been bolstered by appeals to aspects of the
scientific data available and their interpretation.
Most of the controversy regarding these extreme positions has been exposed in
the media which, in general, is much more interested in extreme views than in the
more balanced approach adopted by the IPCC. Particular points that can be
made about the controversy and the attacks that have been directed at the IPCC
are as follows.
1. Amongst the scientists who have contributed to the IPCC there is a wide
range of views — the uncertainty ranges associated with the IPCC
projections of future climate change illustrate this range.
2. All scientists are, of course, interested in genuine scientific debate, the
existence of which is fundamental to scientific advance. Contrary to some of
the allegations that have been made, the IPCC has not tried to inhibit
debate or to minimize the uncertainties that exist.
3. Because, from the wide range of scientific data that exist, it is relatively easy
to select data to support any preconceived conclusion or position, the best
Aviation and the Global Atmosphere, eds. J. E. Penner, D. H. Lister, D. J. Griggs, D. J. Dokken and
M. McFarland, IPCC Special Report published by Cambridge University Press, 1999.
See editorial in Nature, 2001, 412, 103.
J. Houghton
8
Plenary Meeting debated for a considerable time how to express this somewhat
greater scientific confidence in the interpretation of the recent climate record,
although still surrounded by much uncertainty. A sentence carefully crafted by
the meeting was unanimously agreed by the delegates: ‘the balance of evidence
suggests a discernible human influence on global climate’.
Following the 1995 Report, the IPCC produced several Technical Papers in
order to answer particular questions of importance to policymakers. Also several
Special Reports were written addressing particular issues. Of especial importance
was a report on Aviation and the Global Atmosphere carried out in cooperation
with the International Civil Aviation Organisation (ICAO); the authors of the
report included many from the aviation industry. The report addressed the
impact of emissions from aircraft engines on the atmosphere and the climate and
what could be done through engine design or through operational procedures to
minimize the impact. Of particular interest was the result that the influence of
aerosol (small particles) produced from the aircraft emissions together with
emissions of water vapour could have a significant effect on the cloud cover at
aircraft cruising altitudes, with an effect on climate possibly comparable to that of
the carbon dioxide emitted by aircraft.
8 Attacks on the IPCC
The IPCC and its work has been attacked from two fronts; on the one hand by
those who argue that the projections of global warming and its consequences
have been grossly overplayed and that there is no need for any action, and on the
other hand by those who believe that possible serious consequences of global
warming have been ignored and that there is urgent need for much more drastic
action. Both these points of view have been bolstered by appeals to aspects of the
scientific data available and their interpretation.
Most of the controversy regarding these extreme positions has been exposed in
the media which, in general, is much more interested in extreme views than in the
more balanced approach adopted by the IPCC. Particular points that can be
made about the controversy and the attacks that have been directed at the IPCC
are as follows.
1. Amongst the scientists who have contributed to the IPCC there is a wide
range of views — the uncertainty ranges associated with the IPCC
projections of future climate change illustrate this range.
2. All scientists are, of course, interested in genuine scientific debate, the
existence of which is fundamental to scientific advance. Contrary to some of
the allegations that have been made, the IPCC has not tried to inhibit
debate or to minimize the uncertainties that exist.
3. Because, from the wide range of scientific data that exist, it is relatively easy
to select data to support any preconceived conclusion or position, the best
Aviation and the Global Atmosphere, eds. J. E. Penner, D. H. Lister, D. J. Griggs, D. J. Dokken and
M. McFarland, IPCC Special Report published by Cambridge University Press, 1999.
See editorial in Nature, 2001, 412, 103.
J. Houghton
8