The lead authors of the Intergovernmental Panel on Climate Change (IPCC) working group 1, which focuses on the physical sciences, met at ICTP from 26-29 September to kick-off IPCC's fourth assessment report. Rajendra K. Pachauri, IPCC chairman, was among those at the opening session. Susan Solomon (USA) and Dahe Qin (China), co-chairs of working group 1, were also in attendance. The first three rounds of assessment reports (1990, 1995, and 2001) are among the most important scientific reports produced over the past 15 years. The reports are widely credited for bringing the issue of climate change to the forefront of concern among the public and policy makers. Filippo Giorgi, scientific staff member with ICTP's Physics of Weather and Climate group, will serve as one of the chief coordinators of the report.