Researchers tagging a male white shark

A 20th century acceleration in the rate of sea-level rise

Reference: 06/09

Using information from tide gauges and measurements from satellites, Dr John Church and Dr Neil White estimated changes in global mean sea levels since 1870.

31 January 2006

Research by Australian climate scientists has shown that global sea level has been rising at an increasing rate over the past 130 years. Using information from tide gauges and measurements from satellites, Dr John Church and Dr Neil White estimated changes in global mean sea levels since 1870.

Their work, published in the science journal Geophysical Research Letters (6 January), indicates an acceleration in the rate of sea-level rise that had not been detected previously.

‘Although predicted by models, this is the first time a 20th century acceleration has actually been detected,’ Dr Church says. ‘Our research provides added confidence in sea-level rise projections published by the Intergovernmental Panel on Climate Change Third Assessment Report.

‘If the acceleration over the past 130 year period continues, we would expect sea level to be 280-340mm above its 1990 levels by 2100. This is consistent with the projections in the Intergovernmental Panel on Climate Change Third Assessment Report.’

“The research was completed as part of Australia’s Climate Change Science Program, and supported by the Antarctic Climate & Ecosystems CRC and the CSIRO Wealth from Oceans Flagship.”

Church and White’s research indicates that recent sea-level rise began during the first half of the 19th century, when global sea level was about 200 mm below present levels.

‘This is consistent with estimates made from sea-level benchmarks carved in rock in Tasmania in 1840 and the height of ancient Roman fish tanks, implying that there had been little net change in sea level from the first century AD to 1800 AD,’ Dr Church says.

Dr Church says earlier estimates of 20th century sea-level rise had depended on averaging the rates of rise from a limited number of long-term tide gauge records and that the variability in these records made an acceleration difficult to detect.

It was during the same study that Dr Church discovered fluctuations in sea-level rise following volcanic activity, notably the post-1960 eruptions of Mt Agung, Mt Chichon and Mt Pinatubo. In an earlier study, Church, White and Arblaster had shown that these volcanic eruptions masked the late 20th century acceleration that would otherwise have been expected.

The next international assessment of climate change projections will be made by the Intergovernmental Panel on Climate Change in 2007.

The research was completed as part of Australia’s Climate Change Science Program, and supported by the Antarctic Climate & Ecosystems CRC and the CSIRO Wealth from Oceans Flagship.