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ATMOSPHERIC SCIENCE LETTERS
Atmos. Sci. Let. 7: 79–80 (2006)
Published online in Wiley InterScience
(www.interscience.wiley.com) DOI: 10.1002/asl.139
Commentary
Defining the challenge for science in the assessment of
climate change
R. K. Pachauri*
Director General, The Energy and Resources Institute (TERI) and Chairman, Intergovernmental Panel on Climate Change (IPCC)
*Correspondence to:
R. K. Pachauri, Director General,
The Energy and Resources
Institute (TERI) and Chairman,
Intergovernmental Panel on
Climate Change (IPCC).
E-mail: [email protected]
Received: 6 September 2006
Accepted: 6 September 2006
The Intergovernmental Panel on Climate Change
(IPCC) was established in 1988 and has since brought
out three assessment reports as well as several special
reports and technical papers. The Panel is currently
progressing with the completion of the Fourth Assessment Report, all parts of which would be completed
by the end of 2007. The AR-4, as this report has been
labeled, would include several key features, which
reflect the updated findings of the scientific community, addressing major challenges that exist in the area
of climate change. All assessments by the IPCC are
based on accessing and evaluating knowledge contained in peer-reviewed literature. Since the publication of the Third Assessment Report (TAR), significant
advances have taken place in published literature and
in our scientific understanding of the complex range of
factors affecting the earth’s climate system. The TAR,
for instance, had listed a number of key uncertainties,
such as the magnitude and character of natural climate
variability.
On climate change and attribution there are also
questions to be answered on climate forcings due to
natural factors, and anthropogenic aerosols, particularly the indirect effects. Another important issue that
would have relevance to decision making both at the
global and local levels is the need to relate regional
trends to anthropogenic climate change.
Since projections of future climate change are
directly dependent on emission scenarios, which are
driven by projections of economic growth, technological progress, population growth and institutional realities, more research is required to come up with robust
methodologies and projections for reducing uncertainties in this area. The work on scenarios also needs to be
coupled with linkages involving the carbon cycle with
climate feedback. In fact the issue of feedbacks is also
critical in respect to climate sensitivity, climate forcing and feedback processes, especially those involving
Copyright  2006 Royal Meteorological Society
water vapor, clouds and aerosols. Perhaps the most visible effect of climate change would be in the extent
of sea-level rise, and our understanding of this issue
would be enhanced considerably through an understanding of probability distributions associated with
temperature and sea-level projections. Another area
where substantial research and scientific investigations
are required is in respect of the mechanisms, quantification, timescales and specific likelihoods associated with large-scale abrupt/nonlinear changes, such
as ocean thermohaline circulation.
A large number of regional models are currently
in use, the capabilities of which vary substantially. A
great deal of work would be essential in improving
the reliability of these models and perhaps changes in
their structure and character to ensure a higher level of
consistency in projections and quantification of local
and regional change would be of great value. Further,
in regional assessments it would also be essential to
get greater clarity and reliability in climate extremes.
Similarly, the assessments of impacts on ecological
and bio-physical systems in a regional context need
to be carried further in understanding the social and
economic impacts of change, including issues related
to land use change and local pollution.
Along with these, the costs and benefits of mitigation and adaptation options also play a vital role in
defining viable options, and assist the decision maker
in quantifying the uncertainities involved. It is also
essential to understand the interaction between climate
change and other environmental variables and their
related socio-economic implications. The barriers that
impede adoption of low emission technologies should
be identified and the cost of overcoming such barriers needs to be estimated. Similarly, a great deal of
work has to be done in trimming down the uncertainty arising on account of quantification of costs of
unplanned and unexpected mitigation actions, which
80
Commentary
may be unknown today but may become relevant in
the future, owing to likely changes in costs, benefits
and technology.
In the 5 years since the publication of the TAR we
have certainly made some advances in our knowledge
of these key uncertainties related to climate change,
but in the AR-4 efforts have also been made to address
certain key policy-relevant issues, which require integrated treatment of the work of the three working
groups of the IPCC. These so-called cross-cutting
themes (CCT) are as follows:
(1)
(2)
(3)
(4)
(5)
(6)
(7)
Uncertainty and Risk
Integration of Mitigation and Adaptation
Article 2 of the UNFCCC and Key Vulnerabilities
Sustainable Development
Regional Integration
Water
Technology
All of these CCT lend themselves to in-depth treatment, based on linkages between the science of the climate system and knowledge related to impacts, adaptation and vulnerability, as well as all aspects of mitigation of greenhouse gas emissions. However, in respect
to one critical CCT, namely dealing with Key Vulnerabilities as defined in Article 2 of the UN Framework
Convention on Climate Change, science is bound by
certain limitations. The issue of what constitutes a dangerous level of climate change is essentially based on
value judgments. Scientific knowledge can certainly
help human society, and particularly the negotiating
community, to provide precise estimates of what level
and nature of climate change can be considered dangerous, but scientific assessment cannot provide this
answer in itself. Article 2 of the UN Framework Convention on Climate Change (UNFCCC) states that:
‘The ultimate objective of this Convention and any
related legal instruments that the Conference of the
Parties may adopt is to achieve, in accordance with
the relevant provisions of the Convention, stabilization
of greenhouse gas concentrations in the atmosphere at
a level that would prevent dangerous anthropogenic
interference with the climate system’. The Framework
Convention on Climate Change further suggests that
‘such a level should be achieved within a time frame
sufficient
to allow ecosystems to adapt naturally to climate
change,
to ensure that food production is not threatened and
to enable economic development to proceed in a
sustainable manner.’
Since 1992 when the UNFCCC was agreed on, this
particular Article has provided a major challenge to the
international community and negotiators both under
the Convention as well as the Kyoto Protocol (which
was agreed on in 1997 and came into existence in 2005
after requisite ratification by the appropriate Parties to
Copyright  2006 Royal Meteorological Society
the Convention). The scientific community also has
been deeply engaged in addressing this Article, but by
the very nature of the issues embedded in this question,
precise and practical answers have not been possible.
In 2005, the Government of the United Kingdom
organized a major conference in Exeter in an attempt
to throw adequate light on the issue of what constitutes
a dangerous level of climate change. Very valuable
information and analysis was made available in this
conference, which, it is hoped, will help negotiators in
arriving at adequate answers but there is as yet a large
gap to be bridged. Of course, in the AR-4, quite apart
from this issue being treated as a distinct CCT, there
is much information that is being drafted that would
help provide scientific substance for the negotiators to
tackle this question more effectively.
The purpose behind highlighting this particular CCT
in the AR-4 is that this is by far the most intractable
issue that the scientific community faces related to
knowledge in the field of climate change. There would
be a need to consider all elements of the assessment for the question to be tackled effectively, such
as understanding, for instance, the extent, magnitude
and nature of change that would take place in the
earth’s climate system, the impacts that would thus be
created, with emphasis on the vulnerability of different ecosystems, societies and geographical locations,
which would determine their vulnerability. Finally,
due regard has also to be placed on mitigation measures for fully understanding the scientific aspects
of what may constitute a dangerous level of climate
change. For instance if mitigation measures involve
low cost, easily accessible and feasible solutions, then
even those impacts that are likely to take place with
low probability but serious consequences would need
to be addressed as dangerous by policy makers and
those responsible for decision making. If on the other
hand, feasible mitigation solutions are not easily available or prove to be much too expensive, then adaptation measures would have to be resorted to in order to
evade what may constitute a dangerous level of climate
change. Hence, the overall issue related to Article 2 of
the UNFCCC is characterized by complexities that are
likely to defy scientific analysis. Yet the importance of
this subject from a policy perspective requires much
greater effort and research across different regions of
the world to be able to come up with suitable answers
and localized assessment. In the immediate future as
efforts are made to arrive at global agreements beyond
2012, attention would be provided on the long-term
target or limit at which stabilization of the atmosphere
would be attempted. Discussion and debate would then
inevitably center around what would constitute a dangerous level of concentration of GHGs. Scientists and
science can help move knowledge forward in answer
to this question, but cannot, of course, provide the
answer itself.
Atmos. Sci. Let. 7: 79–80 (2006)
DOI: 10.1002/asl
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