NOLA.Com
August 18, 2010
http://www.nola.com/news/gulf-oil-spill/index.ssf/2010/08/scientists_wary_of_us_report_t.html
Published: Tuesday, August 17, 2010, 9:15 PM
Updated: Tuesday, August 17, 2010, 9:25 PM
The Times-Picayune
By Aimee Miles, staff writer
Some scientists are voicing doubts about the accuracy of an Aug. 4 intergovernmental agency report
http://www.deepwaterhorizonresponse.com/posted/2931/Oil_Budget_description_8_3_FINAL.844091.pdf
asserting that just 26 percent of the estimated 4.9 million barrels of oil released from BP’s ruptured wellhead
http://www.nola.com/news/gulf-oil-spill/index.ssf/2010/08/scientists_wary_of_us_report_t.html
remains to be dealt with onshore and at sea.
The highly publicized report,
http://www.nola.com/news/gulf-oil-spill/index.ssf/2010/08/local_officials_environmentali.html
trumpeted on the Aug. 4 front page of the New York Times and unveiled later that day by NOAA Administrator Jane Lubchenco in a White House ceremony attended by Deepwater Horizon incident commander Thad Allen and White House energy adviser Carol Browner, was hailed as a sign of remarkable progress in the Gulf, and led many to question the severity of the spill altogether.
But the report hasn’t marinated well during the past two weeks, attracting increasing criticism from scientists for its dubious conclusiveness and lack of substantiation.
Written by the National Oceanic and Atmospheric
Administration
http://response.restoration.noaa.gov/dwh.php?entry_id=809
in conjunction with the U.S. Geological Survey,
http://www.usgs.gov/
the five-page report includes a pie chart that describes the fate of the oil, broken into seven categories. According to the chart, roughly one-third of the oil that gushed from the wellhead is definitely gone: recovered directly or eliminated by burning, skimming, or chemical dispersion operations.
While that represents roughly 19 percent of the oil removed from the water by response teams, the report reads as if natural processes have eliminated more than twice that amount through evaporation, dissolution or natural dispersion.
Some scientists suspect the figure for oil remaining in the water is much higher than the report’s estimates, and complain that federal officials have refused to reveal the algorithms used to derive the calculations that relied on measurements and estimates provided by Gulf response teams in daily operational reports.
The dearth of supporting data has led to grumbling from environmental scientists, who say they’ll reserve judgment until they can verify the math.
Accusations of obfuscation
A congressional investigator, who asked not to be named, said his repeated requests to NOAA for specific formulas and calculations have gone unmet. The level of obfuscation surrounding the origins of the figures, he said, would never be accepted if the report were presented for publication in an academic journal.
Kerry St. Pe, director of the Barataria Terrebone National Estuary Program, has no confidence in the figures, despite their being reported “as gospel.” Federal scientists can’t determine exactly how much oil has even entered the Gulf, let alone calculate with accuracy what has happened to it since, St. Pe said.
A group of scientists under the Georgia Sea Grant program, part of a NOAA-sponsored university network of ocean and coastal researchers, released an alternative report
http://www.nola.com/news/gulf-oil-spill/index.ssf/2010/08/georgia_scientists_say_80_perc.html
on Tuesday that addresses what they see as faulty conclusions in the federal report.
Their report claims that most of the oil that leaked into the Gulf is still present. They concede that much of it is dissolved or in the form of dispersed micro-droplets, but caution that oil in that state isn’t harmless. According to the Georgia report, between 70 percent and 79 percent of the oil remains in the ecosystem.
Other scientists are also dubious of the specifics in the NOAA report.
“Some members of the scientific community are putting more credibility into what these figures mean than what was meant,” St. Pe said. “They’re just estimates … to give the public a general idea of the fate of the oil and not with any precision.”
‘A ballpark number’
Ed Overton, an LSU environmental scientist who specializes in the chemistry of oil spills, estimates the margin of error in the federal report could be as high as 30 percent. The amount of oil that remains, he said, could be anywhere between a quarter and one-half of the spill’s total volume — a volume that itself is not precisely defined.
Overton, one of 11 independent scientists that NOAA consulted for analysis, said he was contacted by the agency a couple of months ago to provide comments on “significant figures” in early versions of the report. Other scientists consulted included faculty from the University of Calgary and the University of California, San Diego, as well as the chairman of Exxon Mobil’s research and engineering department and BP’s consultant on dispersants and controlled burns, Alan Allen.
Overton said the seeming precision of the Aug. 4 report gave the illusion that federal scientists knew more than they do.
“Models will only give you a ballpark number,” he said. “If you say 24 (percent), you are implying it’s not 23 and it’s not 25.”
The problem, Overton said, is that scientists are using a finite number of variables to model an environmental system that is infinitely complex. That introduces a large margin of error.
Both Overton and St. Pe said the greatest potential for error is contained in the amount of oil said to have evaporated or dissolved. The federal report’s estimate was roughly 1.2 million barrels, or about 30 percent of the oil that entered the Gulf.
‘Your best guess’
Scientists agree that the oil in the Gulf is prone to rapid biodegradation. They believe that because the oil is buoyant, it’s likely to remain closer to the water’s surface, where it may evaporate, disperse or dissolve, or provide food for crude-eating microbes.
But the rates of those natural processes depend on water temperature, weather conditions, currents, and the depth and molecular content of the oil — all of which can be difficult to quantify. “When push coves to shove,” said Overton, “a lot of times you have to put parameters into the model, and sometimes those parameters are your best guess.”
Those best guesses draw upon existing scientific literature from previous spills and from laboratory simulations, which don’t necessarily match Gulf conditions, Overton said. He believes NOAA’s estimate for evaporative losses may actually be conservative, and that the actual amount may be as high as 50 percent.
“I know there’s questions about (the report’s) accuracy, but I think at this point in time it’s the most accurate compilation … that’s available,” said Jay Grimes, a marine microbiologist at the University of Southern Mississippi’s Gulf Coast Research Laboratory.
Grimes also believes the most inconclusive variable is the amount of oil that decomposed at sea.
Functional information
Bill Lehr, the lead scientist on the report, said changes in environmental conditions were taken into account. Although conditions at sea changed from day to day, Lehr said averaging the numbers would smooth out differences. He said NOAA’s figures were consistent with experiments performed in Canada and Norway.
“The unusual feature of this was the spill being a mile deep and therefore we would have some components that would normally evaporate dissolved in the water column,” Lehr said.
For that reason, the report groups evaporation and dissolution into a single category.
Lehr believes the budget’s greatest uncertainties are not in its evaporation and dissolution rates, as other scientists have claimed, but in the rates of dispersion.
Parts of the oil-gas mixture that exited the wellhead dispersed naturally, Lehr said, but the fluid dispersal rate is a calculated estimate, and not a measurement. Lehr said other sources have suggested that the dispersants may be more effective than what NOAA presumed, which could mean the report is also conservative in this aspect. But as oil emulsifies at the water’s surface, it becomes stickier, which also renders dispersants less effective, he acknowledged.
Other questions persist.
While the report said only 3 percent of the oil spilled was picked up by skimmers, that number is likely high, Lehr said, because skimmers’ measurements include both oil and water.
Lehr said the federal report, whose figures have been widely discussed by the media, was meant to provide functional information to the incident command, not to stand up to rigorous academic evaluation.
He expects a more detailed report on the oil budget will soon be released, one that contains data, assumptions, references, and comments from peer reviewers.
“It’ll be what people are used to seeing in terms of a scientific report,” Lehr promised.
Aimee Miles can be reached at amiles@timespicayune.com or 504.826.3318.
Special thanks to Richard Charter