Effects on the oceans
Increased global temperatures will lead to rises in sea level due to the melting of the ice caps and thermal expansion of water. This in itself will lead to coastal erosion and habitat loss in places such as marshes, dunes, mangroves swamps and coral reefs, and the salinisation (more salty) of estuaries, coastal rivers and soils.
Melting of the polar ice caps releases 1,000s of gallons of freshwater into the sea. This may disrupt the ocean currents, which are driven by differences in density and temperature of water. One such current known as the Atlantic Conveyor warms the UK. Without it we would have temperatures similar to Canada and possibly polar bears!