Buckets of Saltwater

AAAS: "Is the world 1.3ºC or 1.5ºC warmer? Historical ship logs hold answers." Historical baseline ocean temperatures are disputed. "One group of climate scientists found the planet has warmed 1.34°C over the 1850–1900 average, whereas another found temperatures had risen 1.54°C." The dispute is not about current temperatures, where statistical techniques can extrapolate between measuring stations. Instead the question is discrepancies in late 19th century data. “The impetus to resolve this is getting bigger,” says Robert Rohde, the lead scientist of Berkeley Earth, one of the 5 main groups that produce a global record. This began "began in the 1850s thanks to a controversial figure, Matthew Fontaine Maury, a superintendent at the U.S. Naval Observatory who avidly supported slavery." Competiting with the East India Company, Maury encouraged merchant sailors to collect observations, including water temperature heaved to the decks in buckets. "Over time, wooden buckets gave way to canvas and rubber ones, and when steam ships took over, sailors began to measure water temperatures first through engine intake valves and later with sensors along the hull." But canvas buckets posed risk of evaporative cooling. Intake valves were warmed by the ship itself, with the opposite bias. "Today, two organizations maintain these historical sea surface temperature records: the U.S. National Oceanic and Atmospheric Administration (NOAA) and the U.K.’s Met Office." NOAA cross-checks the bucket temperature with air temperatures determined at the same time + place. The Met [Meteorlogical] Office relies on a 'bucket model.' But utilizing temperatures from nearby island or coastal weather stations seems to better compensate for the bucket biases, which 'also line up betterwith temperature records inferred from tree rings and corals.' "Elizabeth Kent, a climatologist at the U.K.’s National Oceanography Centre, and colleagues hunt for overlooked details in the logbooks that can help them identify unknown ships and infer their data collection methods," but a staggering number of logbooks haven't been digitized yet. Time to hop to it, perhaps with AI assistance.