ICES, PICES and IOC joined forces in 2008 for the first global ocean symposium (Gijón, Spain) and it attracted 400 scientists from 48 countries. This second look at the “Effects of Climate Change on the World’s Oceans” will lead us through many issues of the role of climate change on the oceans: sea level rise, changes in thermo-haline ocean circulation, acidification, oligotrophy of temperate seas, changes in species abundance, distribution and phenology, loss of biodiversity, all of which will have serious implications for marine living resources, etc. This symposium aims to bring together experts from different disciplines to exchange observations, results, models and ideas at a global scale and to discuss the opportunities to mitigate and protect the marine environment and its living resources.