A study published today in the global science journal Nature reveals the bulk of ocean temperature data collected from 1961 and used by climate modelling to calculate the rate at which our oceans are warming are not accurate because of a manufacturing fault in the equipment used.

''The rate of ocean warming and sea level change as a result of climate change is significantly greater than was previously thought. We need to revise some of those earlier estimates,'' CSIRO's Wealth From Oceans principal research scientist Dr John Church said.

Simple probes known as expendable bathythermograph or XBTs were previously used by oceanographers to measure ocean temperatures. The probe was dropped from a research ship and two small wires measured temperature changes as it fell through the water, transmitting data to the ship.

The CSIRO study reveals these probes superseded since 2001 by robotic Argo floats which provide year-round data had manufacturing faults which led to ''significant systematic biases'' in data. These were chiefly errors in the estimated depths of ocean temperature observations.

''We were able to figure out a way to correct or minimise that bias in the historical data,'' CSIRO researcher Dr Susan Wijffels said.

The Hobart-based CSIRO climate science team analysed millions of ocean measurements and found the world's oceans warmed and sea levels rose at a rate 50 per cent faster in the last four decades of the 20th century than documented in the most recent report by the Intergovernmental Panel on Climate Change.

The findings published in Nature say ocean warming and thermal expansion ''are more than 50 per cent larger than for previous estimates'' for the upper 300m of the ocean and ''about 50 per cent larger'' for the upper 700m.

Dr Wijffels said the research gave ''significantly greater credibility'' to climate models predicting the degree of warming of the world's oceans.

''We can now see more detail ... and we can also see that we have potentially under-estimated the rate of ocean warming.''

The disposable probes accounted for 70 per cent of historical ocean temperature data. When the CSIRO team developed a method to correct the instrument bias in these records, they were able to arrive at a more accurate estimate of upper-ocean warming and thermal expansion.

''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,'' CSIRO researcher Dr Catia Domingues said.

The results will boost confidence in climate models used for projections of global sea-level rise resulting from the build-up of heat in the oceans, which will assist in planning to minimise impacts and develop adaptation strategies, Dr Domingues said.