Summary/Abstract
The reliable detection and attribution of changes in climate, and their effects, is fundamental to our understanding of the scientific basis of climate change and in enabling decision makers to manage climate-related risk. This paper summarises the discussions and conclusions of the joint Expert Meeting of Working Group I and Working Group II of the Intergovernmental Panel on Climate Change (IPCC WGI/WGII) on ”Detection and Attribution related to Anthropogenic Climate Change”, which was held in Geneva, Switzerland on 14-16 September 2009. It seeks to clarify methods, definitions and terminology across the two working groups and is intended as a guide for future IPCC Lead Authors. This paper also outlines guidelines for how to assess the relative quality of studies and provides recommendations for good practice in detection and attribution studies. In this respect, it discusses criteria for assessing confidence, outlines data requirements and addresses methods for handling confounding factors.