Academic scientists quoted in stories late last week by NPR  and The New York Times  suggested that the amount of oil spewing out from the broken pipe on the gulf floor may be much more than 5000 barrels (794,936 gallons) per day—the official estimate of both BP and the government for the first 3 weeks of the crisis, before BP made any progress in stanching the flow. Newly released video and satellite data, they say, along with back-of-the-envelope calculations, suggest there could be as much as 10 times more oil gushing out  of the Deepwater pipe than officials are saying. Hours before the stories appeared on 13 and 14 May, White House science adviser John Holdren told an audience in Washington, D.C., that "you can't make direct flow measurements" of the gusher but failed to mention the satellite or video techniques.
"It's very hard to make measurements down there," Holdren said. The fact that the leak is a mixture of oil, water, and gas complicates the challenge, he added. The following day, President Obama said  "there have been varying reports over the last few days about how large the leak is, but since no one can get down there in person, we know there is a level of uncertainty. ... What really matters is this: There's oil leaking and we need to stop it—and we need to stop it as soon as possible."
Today in a written statement to ScienceInsider, Holdren suggested that traffic among the submersibles is among the reasons that the government doesn't know more about the size of the leak:
A reason that there has not been more effort to get better flow estimates at the source(s) up until now, beyond the inherent difficulties, is that higher priority has been given to actions that could stop the flow rather than to actions that could measure it.
There have been 7 or 8 Remotely Operated Vehicles down there fully occupied with missions related to stopping it, and the congestion involved with this many ROVs, their control vessels above, and the cables in between has led to the judgment that trying to add any more would be counterproductive. But scientists involved in these efforts ARE working on ways to get better flow measurements out of the existing ROV complement.
Holdren had called it a "problematic proposition" that "we do not know whether it is 5000 barrels a day or 10,000 or 2000. ... The one thing we do know is that it could be more if it gets worse down there," added Holdren. "And so it's very important to get this thing plugged, rather than making itself worse or make a misstep in our efforts to plug it that would make it worse. "
The National Oceanic and Atmospheric Administration's estimate was made using the size of the spill on the surface.
For more on the gulf oil spill, see our full coverage .