This extended report of the IPCC Expert Meeting on the Science of Alternative Metrics that was held in Oslo 18-20 March 2009 is provided in response to an invitation from the UN Framework Convention on Climate Change Ad Hoc Working Group on Further Commitments for Annex I Parties under Kyoto Protocol (UNFCCC AWG-KP) to the Intergovernmental Panel on Climate Change (IPCC) to undertake further technical assessment of alternative common metrics which are used to calculate the CO2 equivalence of anthropogenic emissions by sources, and removals by sinks, of greenhouse gases listed in Annex A to the Kyoto Protocol. The outcome of the expert meeting was an agreed set of key conclusions and recommendations to UNFCCC in response to the request of the AWG-KP as well as more specific recommendations to the scientific community regarding research needs and ones relevant to the scoping of the IPCC's Fifth Assessment Report (AR5). These were presented to the IPCC Plenary in a short report at its 30th session in Antalya, 21-23 April 2009. The current full report of the expert meeting amplifies those conclusions and recommendations and includes the extended abstracts of the meeting presentations as well as a general bibliography.

This meeting focused on the future of the IPCC, in particular the scoping of the 5th Assessment Report. Among other isues, the Panel considered the outcome of the Scoping Meeting for a possible Special Report on "Extreme events and disasters: managing the risks", and of the Expert Meeting on "Alternative common metrics to calculate the CO2 equivalence of anthropogenic emissions by sources and removals by sinks of greenhouse gases".