The paper evaluates and compares the risks of impacts on marine and coastal ecosystems and the goods and services they provide under two contrasting emissions scenarios: a current trajectory of high carbon emissions and a reduced emissions scenario consistent with the Copenhagen Accord's goal of limiting global temperature increase to less than 2°C. The current trajectory would rapidly and significantly alter many ecosystems and associated services, while the reduced emissions scenario, though less severe, still significantly alters important marine ecosystems. The policy options to address these impacts narrow as the ocean warms and acidifies, emphasizing the urgency of reducing carbon emissions to minimize ocean impacts. The paper highlights the high risks associated with a 2°C warming of global surface temperature and argues that any new climate regime that fails to minimize these impacts would be incomplete and inadequate.The paper evaluates and compares the risks of impacts on marine and coastal ecosystems and the goods and services they provide under two contrasting emissions scenarios: a current trajectory of high carbon emissions and a reduced emissions scenario consistent with the Copenhagen Accord's goal of limiting global temperature increase to less than 2°C. The current trajectory would rapidly and significantly alter many ecosystems and associated services, while the reduced emissions scenario, though less severe, still significantly alters important marine ecosystems. The policy options to address these impacts narrow as the ocean warms and acidifies, emphasizing the urgency of reducing carbon emissions to minimize ocean impacts. The paper highlights the high risks associated with a 2°C warming of global surface temperature and argues that any new climate regime that fails to minimize these impacts would be incomplete and inadequate.