Global warming is one of the greatest threats to humankind and it has been suggested that marine organisms are more vulnerable to warming than terrestrial organisms. Understanding how enzymatic, genetic and physiological characteristics of individual organisms change in response to increasing mean temperature and temperature fluctuations and how these individual responses scale up to the community, ecosystem and eventually global biogeochemical cycles is a challenging scientific task. Important knowledge gaps exist at all these different scales. At the molecular level, for example, how are the activity and three-dimensional structure of key enzymes such as RubisCO affected by temperature? At the individual level, what are the general patterns of thermal reaction norms and how do they differ between species and habitats? How do species composition, coexistence, and diversity change as temperature changes, particularly with increasing temperature variability? Will these ecological responses translate into changes in biochemical fluxes like global photosynthesis, metabolism and carbon export, which will in turn cause feedbacks to Earth’s climate?  This session welcomes empirical and modelling studies at all these different scales and will act as a platform to comprehensively understand warming effects from organismal physiology to ecosystem processes in a dynamic and changing ocean.