The Intergovernmental Panel on Climate Change (IPCC) was jointly established by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) to assess the scientific, technical and socio-economic information relevant for the understanding of the risk of human-induced climate change. Since its inception the IPCC has produced a series of comprehensive Assessment Reports on the state of understanding of causes of climate change, its potential impacts and options for response strategies. It prepared also Special Reports, Technical Papers, methodologies and guidelines. These IPCC publications have become standard works of reference, widely used by policymakers, scientists and other experts.

In 1992 the IPCC released emission scenarios to be used for driving global circulation models to develop climate change scenarios. The so-called IS92 scenarios were pathbreaking. They were the first global scenarios to provide estimates for the full suite of greenhouse gases. Much has changed since then in our understanding of possible future greenhouse gas emissions and climate change. Therefore the IPCC decided in 1996 to develop a new set of emissions scenarios which will provide input to the IPCC third assessment report but can be of broader use than the IS92 scenarios. The new scenarios provide also input for evaluating climatic and environmental consequences of future greenhouse gas emissions and for assessing alternative mitigation and adaptation strategies. They include improved emission baselines and latest information on economic restructuring throughout the world, examine different rates and trends in technological change and expand the range of different economic-development pathways, including narrowing of the income gap between developed and developing countries. To achieve this a new approach was adopted to take into account a wide range of scientific perspectives, and interactions between regions and sectors. Through the so-called "open process" input and feedback from a community of experts much broader than the writing team were solicited. The results of this work show that different social, economic and technological developments have a strong impact on emission trends, without assuming explicit climate policy interventions. The new scenarios provide also important insights about the interlinkages between environmental quality and development choices and will certainly be a useful tool for experts and decision makers.

As usual in the IPCC, success in producing this report has depended first and foremost on the co-operation of scientists and other experts worldwide. In the case of this report the active contribution of a broad expert community to the open process was an important element of the success. These individuals have devoted enormous time and effort to producing this report and we are extremely grateful for their commitment to the IPCC process. We would like to highlight in particular the enthusiasm and tireless efforts of the co-ordinating lead author for this report Nebojsa Nakicenovic and his team at the International Institute for Applied Systems Analysis (IIASA) in Laxenburg/Austria who ensured the high quality of this report.

Further we would like to express our sincere thanks to:

• Robert T. Watson, the Chairman of the IPCC,
• The Co-chairs of Working Group III Bert Metz and Ogunlade Davidson,
• The members of the writing team,
• The staff of the Working Group III Technical Support Unit, including Rob Swart, Jiahua Pan, Tom Kram, and Anita Meier,
• N. Sundararaman, the Secretary of the IPCC, Renate Christ Deputy Secretary of the IPCC and the staff of the IPCC Secretariat Rudie Bourgeois, Chantal Ettori and Annie Courtin.

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