After months of gloom, last week's report on the fate of the oil from BP's Deepwater Horizon spill offered a rare piece of good news. "At least 50% of the oil that was released is now completely gone from the system," said Jane Lubchenco, administrator of the National Oceanic and Atmospheric Administration (NOAA), at a White House press conference on 5 August. That welcome figure came from an effort to tally what has happened to the three-quarters of a billion litres of oil that have poured into the Gulf of Mexico since April.
But although researchers have embraced some of the report's messages, many contacted by Nature point out that it fails to convey the substantial uncertainties in some of its estimates. "In my mind it's scientifically indefensible," says James Cowan, an oceanographer at Louisiana State University in Baton Rouge. Some question whether the timing of the report, released as BP announced that it had succeeded in plugging the damaged well, was driven more by politics than science.
The report estimates that about a quarter of the spilled oil was captured, burned or skimmed off the ocean; that another quarter was dispersed into tiny droplets, either naturally or with chemical dispersants; and that a quarter evaporated or completely dissolved. The remaining quarter, determined by subtraction, is assumed to be floating on the ocean's surface or already washed ashore (see graphic). Most of this remainder "is degrading rapidly or is being removed from the beaches", said Lubchenco, adding that there was a "high degree of confidence" in the numbers. She cautioned, however, that dissolved or dispersed oil could still pose threats to marine life.
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