The Arctic Climate Impact Assessment process (ACIA; see http://www.acia.uaf.edu/) is an international project of the Arctic Council and the International Arctic Science Committee (IASC) to evaluate and synthesize knowledge on climate variability, climate change, increased ultraviolet radiation, and their consequences. As a part of the Norwegian work within ACIA (see http://acia.npolar.no/), an international workshop on Arctic climate feedback mechanisms was held in November 2003 at the Norwegian Polar Institute. Invited talks were presented in five sessions focused on climate programs, terrestrial systems, oceans, sea ice, and atmosphere. Poster presentations and working groups were organized for four sessions in the various scientific fields, identifying the state of knowledge and challenges, and making recommendations.