Assessing impact of climate change on marine environment

This strategy features in the framework of Agenda 21 as formulated at UNCED (Rio de Janeiro, 1992), now coordinated by the United Nations Commission on Sustainable Development and implemented through national and local authorities.

There is a growing understanding of the possible impact of climate change on the marine environment, for example through more evaporation from warmer seas increasing atmospheric humidity and thus reinforcing the greenhouse effect (Epstein 1997). Until recently, attention has focused on the impact on small island states and low-lying countries of a rise in sea level and an increase in the frequency or intensity of storms resulting from climate change. There could, however, be more complex effects. For example, if warming continues, freshwater from melted Arctic ice may form a cap on the Norwegian and Greenland Seas, resulting in changes to deep ocean circulation patterns that might divert to the south the waters of the Gulf Stream that presently keep western Europe warm in the winter (Broecker 1997).

Surface warming and increased thermal stratification may also reduce phytoplankton productivity, which forms the basis of the entire marine food chain. A build-up of carbon dioxide in the atmosphere can lead to increased acidity of the surface ocean (Epstein 1997) which, together with UV-B penetration, can also reduce phytoplankton productivity; it can also change the carbonate content in surface waters, which could interfere with coral growth. Extensive coral bleaching has also recently been associated with the warming of surface waters (Pomerance 1999).