WASHINGTON - The Obama administration struggled behind the scenes to determine how much oil spilled in the Gulf of Mexico from a BP well this year and defended estimates that for months were inaccurate, according to thousands of government e-mails.
A senior scientist who led the federal effort, Bill Lehr of the National Oceanic and Atmospheric Administration, noted that the administration went public with a summary of estimates before experts could finish their work.
An Environmental Protection Agency memo, one of many showing uncertainty, said, "EPA agrees that the ultimate message to the public will likely be that the oil was successfully dispersed with chemical dispersants, but until we know with some degree of certainty . . . we are hesitant to assign distinct percentages at this time."
Lehr said the calculations made public represented "our best guess," adding, "Yes, it is a guess."
The government said this week that its final estimate, of 172 million gallons of oil poring into the ocean between April 20 and July 15, was accurate.
The behind-the-scenes e-mails hint at uncertainties in what the government knew during the summer, even as its scientists wrestled over how to measure oil leaking from a runaway well a mile under the ocean.
EPA Administrator Lisa Jackson was "concerned about the level of certainty implied in the pie and cylinder charts." Another e-mail noticed that a pie chart in a draft of the government's report wasn't actually round: "A pie chart pretty much has to round to 100," NOAA spokeswoman Jennifer Austin wrote.
An e-mail from EPA official Bob Perciasepe to other U.S. officials warned: "I think you are making a mistake on the separate estimates of dispersal but I have no additional arguments other than it is not verifiable and we will be trying to explain it for the rest of our time on this. I will take it up with White House."
Lehr's top boss at NOAA, Jane Lubchenco, cautioned a colleague about how to present the government's findings. "I believe we owe it to everyone to provide the best estimates we can where direct measurements are not possible," she wrote. "We also need to be forthright about how certain we are about each number, which we've done."
The e-mails were obtained by The Associated Press under the Freedom of Information Act.
The documents released Wednesday by the Commerce Department, NOAA's parent agency, were significant because they revealed conversations among scientists working on the forecasts of oil in the Gulf. The government released 5,817 pages of files late in the afternoon on the eve of Thanksgiving, traditionally a period when few people are paying attention to news reports because of holiday travel.