During the last ice age, when much of the water on Earth was frozen, sea levels were about 120 metres lower than they are today.Around 20,000 years ago, we started coming out of the ice age and the ice melted.Sea levels then started to rise fairly rapidly, about one metre over a century, with the fastest rates of about four metres in a century.But over the past few thousand years, during a period of relative climatic stability, sea level has been fairly stable, with very little change between about 1 AD and 1800 AD.