Ocean warming may well turn out to be the greatest hidden challenge of our generation. Whilst some may be aware of the challenges a warming ocean presents to coral reefs, few know about the other consequences this holds for the ocean. Ocean acidification emerged as a new story around 2004, with problems already being encountered due to changes in ocean chemistry, and yet add ocean warming and there is a far bigger story to tell. In this report, we assess the scale of the challenge and explore this issue from a range of different perspectives – oceanography, ecosystems and species. We also look at the impacts ocean warming might have on the every-day benefits we derive from the ocean – its ‘goods and services’.