The Fourth Assessment Report of the Intergovernmental Panel on Climate Change states that warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level. Natural systems, including oceans and coasts, are being affected by regional climate changes, particularly by temperature increases. Besides rising surface water temperatures and sea level, impacts are or will be associated with changes in the wave climate, circulation, ice cover, fresh water run-off, salinity, oxygen levels and water acidity.
Shifts in ranges and changes in algal, plankton and fish abundance have already been observed in high-latitude oceans. Besides these there are other effects that, based on published literature, have not yet become established trends as they are difficult to discern due to adaptation and non-climatic drivers. Sea level-rise is negatively contributing to coastal erosion, losses of coastal wetland ecosystems, including salt marshes and mangroves, and increasing damage from coastal flooding in many areas. These effects will be exacerbated by increasing human-induced pressures on coastal areas.