Sea level has risen about 130 metres (400 feet) since the peak of the last ice age about 18,000 years ago. Most of the rise occurred before 6,000 years ago. From 3,000 years ago to the start of the 19th century sea level was almost constant, rising at 0.1 to 0.2 mm/yr. Since 1900 the level has risen at 1 to 2 mm/yr; since 1992 satellite altimetry from TOPEX/Poseidon indicates a rate of rise about 3 mm/yr. The IPCC TAR notes, however, "No significant acceleration in the rate of sea level rise during the 20th century has been detected."
Sea level rise can be a product of global warming through two main processes: expansion of sea water as the oceans warm, and melting of ice over land. Global warming is predicted to cause significant rises in sea level over the course of the twenty-first century.