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
1/--страниц