Jason Lowe Hadley Centre for Climate Prediction and Research
Tide gauge measurements suggest that global average sea level has risen during the 20th century by between 1 and 2mm/yr. Recent satellite altimeter measurements, which have better spatial coverage than the tide gauges but span a much shorter time period, indicate that between 1993 and 2003 the rate of rise was around 3mm/yr. At present it is unclear whether this apparent increase in rate is due to natural variability of the climate or is part of a long-term acceleration in the rate of rise.
During the 21st century we predict, with a high confidence, that the global average sea level will rise. However, we have only a low to moderate confidence in the magnitude of the rise. The third assessment of the IPCC presented a range of projected sea-level rise between 1990 and 2100 of 9-88cm, with the largest contribution coming from thermal expansion. This range aims to account for uncertainty in the emissions scenario and in the modelling techniques.
We do not expect the pattern of time average sea-level rise to be spatially uniform. We have a low to moderate confidence in the prediction that some locations will experience future increases of around 50% more than the global average, but the confidence in where this will occur is very low. We can not yet rule out the regional enhancement occurring in the North Atlantic, where it might affect UK waters. When considering flooding the vertical movement of the land must also be included, giving a relative sea level change. The vertical land movement varies considerably with location.
HIGH
High confidence that the global average sea level will rise.
LOW
Low to moderate confidence in the magnitude of the rise.
Low to moderate confidence in the prediction that some locations will experience future increases of around 50% more than the global average, but the confidence in where this will occur is very low.
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Please acknowledge this document as: Lowe, J. (2006). Impacts of Climate Change on Sea Level in Marine Climate Change Impacts Annual Report Card 2006 (Eds. Buckley, P.J, Dye, S.R. and Baxter, J.M), Online Summary Reports, MCCIP, Lowestoft, www.mccip.org.uk
