Scientific investigation has uncovered a long-standing error in ocean temperature measurements, revealing that the world's seas are warming and rising at a faster rate than previously believed. An international team of scientists discovered the error in data from a common probe known as an XBT, after analyzing millions of ship-based measurements dating back to 1950, with a focus on data from 1960 onwards. By correcting the error and applying a complex statistical analysis to sea temperature data, the team determined a global estimate of ocean warming in the top layers down to 700 meters, as well as the speed at which oceans are rising. According to team member Catia Domingues, the rate of ocean warming from 1961 to 2003 is approximately 50 percent higher than previously reported. John Church, another author of the report, had suspected inaccuracies in historical data due to discrepancies with results from climate and ocean models. "We have adjusted our observations and as a result, the models now align much better with the observations," stated Church, a senior research scientist at the climate center. By comparing XBT observations with research ship data in a statistical manner, one can estimate the errors associated with XBTs. This is important because oceans hold over 90 percent of the heat in the planet's climate system and can help mitigate the impacts of climate change, explained Domingues. As water warms, it expands, leading to rising sea levels along with run-off from melting glaciers and ice sheets in Greenland and Antarctica. Church's team estimated a global average surface warming of 0.4 degrees Celsius between 1961 and 2003, with seas rising an average of 1.6 millimeters per year during this time period. Since 1993, sea levels have been rising at a rate of more than 3 mm per year due to increased consumption of fossil fuels. Previously, XBTs were commonly used by commercial vessels to measure ocean temperatures, but they have been largely replaced by satellites and permanent probes. XBTs were disposable instruments that were thrown overboard with a wire attached to measure temperatures as they sank. A miscalculation in the instrument's fall through the water column could result in errors in depth and temperature readings. To address this issue, Susan Wijffels and her colleagues developed a mathematical formula to correct the errors. When looking at a broader range of global ocean temperature data, it became evident that the data aligned more closely with widely used computer models that predict climate and ocean behavior due to global warming. This discovery has increased confidence in the accuracy of these models for future projections, as well as indicated that sea level rise is tracking towards the higher end of projections. The latest global assessment by the U.N. Climate Panel suggested that sea levels could potentially rise by up to 80 cm by 2100 if carbon dioxide levels are not controlled.