The Third Assessment Report of the IPCC's Working Group 1 builds on past assessments and incorporates new results from the past five years of climate change. It descibes the current state of udnerstanding of the cliamte system, and provides estiamtes of its projected future evolution and their uncertainties.

Many hundreds of scientists from around the world participated in the preparation and review of the report, which states that "there is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities".