New study corrects sea temperature rise data

by Rich Bowden - Jun 19 2008, 19:34

According to new computer modelling released by Australian and U.S. scientists, sea temperatures have been warming around fifty percent faster over the last forty years than previously thought.

The research, led by the Centre for Australian Weather and Climate Research, found that from 1961 to 2003, the world's seas had warmed at a rate around 50 percent faster than that previously documented and more in line with estimates contained in the 2007 Intergovernmental Panel on Climate Change Report (IPCC AR4).

The team found sea temperatures rises to a depth of 700 metres, had contributed to an average rise in sea levels of 0.52 millimetre-per-year compared to a 0.32 millimetre rise originally reported.

The worst case scenario better illustrates the way climate models simulate the degree of warming in the world's oceans and, with thermal expansion a major factor in rising sea levels, gives added impetus to environmentalists' fears of the damage rising levels will have on low-lying regions of the world.

“For the first time, we can provide a reasonable account of the processes causing the rate of global sea-level rise over the past four decades – a puzzle that has led to a lot of scientific discussion since the 2001 IPCC report but with no significant advances until now,” says CSIRO Wealth from Oceans National Research Flagship scientist, Dr Catia Domingues, from the Centre for Australian Weather and Climate Research.
                              
“Following the review of millions of ocean measurements, predominantly from expendable instruments probing the upper 700 metres of the ocean, we were able to more accurately estimate upper-ocean warming, and the related thermal expansion and sea-level rise. “We show that the rate of ocean warming from 1961 to 2003 is about 50 per cent larger than previously reported,” Dr Domingues says.

In correcting previous studies, scientists found "significant biases" in measurements from expendable bathy-thermographs (XBTs), which had been in use since the 1960s and had constituted more than seventy percent of the data.

"Significant biases in XBT temperatures are associated primarily with errors in the estimated depth of observations, probably a result of subtle differences in the manufacture of the XBTs," the researchers say.

Adjusting the measurements  gave a better match between the data and observation.

The findings of the study are published inthe journal Nature and the team included researchers from the Centre for Australian Weather and Climate Research, the Antarctic Climate and Ecosystem Cooperative Research Centre and the Lawrence Livermore National Laboratory, California USA.  Co-authors were John Church, Neil White, Peter Gleckler; Susan Wijffels, Paul Barker and Jeff Dunn.                                                                                                                                                                                    

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