Government representatives and scientists opened a meeting of the Intergovernmental Panel on Climate Change (IPCC) on Monday to finalize a report assessing the evidence for climate change and its causes. The meeting, the culmination of four years’ work by hundreds of experts who have volunteered their time and expertise to produce a comprehensive assessment, will approve the Summary for Policymakers of the first part of the IPCC’s Fifth Assessment Report, subjecting it to line-by-line scrutiny. It will also accept the full report, which includes a Technical Summary, 14 chapters and several annexes, including, for the first time, an Atlas of Global and Regional Climate Projections. This first part of the report, produced by the IPCC’s Working Group I, deals with the physical science basis of climate change. Further contributions, by IPCC Working Group II dealing with the impacts, adaptation and vulnerability relating to climate change, and by Working Group III assessing the mitigation of climate change, will be finalized in March and April 2014 respectively. The Fifth Assessment Report will be completed by a Synthesis Report in October 2014.