Current Sea Level Rise - Future Sea-level Rise - IPCC Third Assessment

IPCC Third Assessment

The results from the IPCC Third Assessment Report (TAR) sea level chapter are given below.

The sum of these components indicates a rate of eustatic sea level rise (corresponding to a change in ocean volume) from 1910 to 1990 ranging from −0.8 to 2.2 mm/yr, with a central value of 0.7 mm/yr. The upper bound is close to the observational upper bound (2.0 mm/yr), but the central value is less than the observational lower bound (1.0 mm/yr), i.e., the sum of components is biased low compared to the observational estimates. The sum of components indicates an acceleration of only 0.2 (mm/yr)/century, with a range from −1.1 to +0.7 (mm/yr)/century, consistent with observational finding of no acceleration in sea-level rise during the 20th century. The estimated rate of sea-level rise from anthropogenic climate change from 1910 to 1990 (from modeling studies of thermal expansion, glaciers and ice sheets) ranges from 0.3 to 0.8 mm/yr. It is very likely that 20th-century warming has contributed significantly to the observed sea-level rise, through the thermal expansion of sea water and the widespread loss of land ice.

A common perception is that the rate of sea-level rise should have accelerated during the latter half of the 20th century, but tide gauge data for the 20th century show no significant acceleration. Estimates obtained are based on atmosphere-ocean general circulation models (abbreviated AOGCMs) for the terms directly related to anthropogenic climate change in the 20th century, i.e., thermal expansion, ice sheets, glaciers and ice caps... The total computed rise indicates an acceleration of only 0.2 (mm/yr)/century, with a range from −1.1 to +0.7 (mm/yr)/century, consistent with observational finding of no acceleration in sea-level rise during the 20th century. The sum of terms not related to recent climate change is −1.1 to +0.9 mm/yr (i.e., excluding thermal expansion, glaciers and ice caps, and changes in the ice sheets due to 20th century climate change). This range is less than the observational lower bound of sea-level rise. Hence it is very likely that these terms alone are an insufficient explanation, implying that 20th century climate change has made a contribution to 20th century sea-level rise. Recent figures of human, terrestrial impoundment came too late for the 3rd Report, and would revise levels upward for much of the 20th century.