fore his death, claimed that thermal expansion of seawater was not well documented. Leroux argued that if seawater expands with changes in temperature, such expansion should be apparent with the changes in the seasons. In other words, sea levels should be higher in the summer, when it is hot, than in the winter, when it is colder. Working with data from the tide-gauge at Brest in France, Leroux concluded that "variations in water levels and temperatures are not synchronous at Brest; the highest (positive) values do not occur in summer, but in autumn-winter."2 In other words, sea levels were higher in winter than in summer, which is the opposite of what one would expect if thermal expansion were occurring. Leroux does not explain why sea levels were higher in winter, and there might be any number of reasons for it, but the fact remains that his data did raise some questions about thermal expansion.
Another researcher who discovered data that seemed to contradict thermal expansion was Josh Willis, a scientist at NASA's Jet Propulsion Laboratory. Willis works on estimating the amount of heat in the ocean. In 2004, Willis published a study showing that the ocean heat rose from 1993 to 2004. In 2006, he did a follow-up study—but much to his surprise, the research now showed the ocean cooling from 2003 to 2005. This result was especially confusing because other data showed that ocean levels during that period were rising. Willis himself believed that the data simply demonstrated natural variation in temperature. Others though "cited the results as proof that global warming wasn't real and that climate scientists didn't know what they were doing."3
In 2007, however, Willis discovered that he had been in error. The ocean cooling he had discovered did not exist. His data had been bad, and in fact the ocean had warmed between 2003 and 2005. The revised data turned out to be very important in calculating sea-level rise. According to Catia Domingues, a scientist with Australia's Commonwealth Scientific and Industrial Research Organisation, using Willis's new data allowed researchers to see "that ocean heating was larger than scientists previously thought, and so the contribution of thermal expansion to sea level rise was actually 50 percent larger than previous estimates."4
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