Drayton's Gazette discusses social and political issues happening around the globe through the eyes of the African American, minority and disaffected communities.

From the Union of Concerned Scientist

Deepwater Horizon Oil Spill: Amount of Oil

Rating: Foothill

The Charges

Following the Deepwater Horizon Oil Spill, the United States government significantly underestimated the amount of oil spilling into the Gulf of Mexico. In the weeks after the disaster, independent scientists were able to provide estimates that were much closer to the actual amount of oil leaked, yet government estimates remained unchanged for nearly a month.

On April 20, 2010, the Deepwater Horizon underwater drilling rig exploded off the coast of Louisiana, killing several workers and causing a hole in a BP deepwater well. Following the explosion, the government reported estimates for the amount of oil flowing into the Gulf of Mexico, and later, the amount of oil that was left in the Gulf when the well was capped. Both the initial flow rate estimate and the amount of remaining oil estimates were significantly lower than those of independent scientists.

After an initial estimate of 1,000 barrels per day (bbls/day), the National Oceanic and Atmospheric Administration (NOAA) provided an estimate of 5,000 bbls/day one week after the explosion. Despite the acknowledged inaccuracies of the NOAA estimate, and despite the existence of other and potentially better methodologies for visually assessing flow rate, the 5,000 bbls/day remained the official government estimate until May 27, 2010.(1)

Comparison of Government and Independent Estimates of Oil

Date Government Estimate (bbls/day) Independent Scientists’ Estimate (bbls/day)
April 24 1,000(2)
April 27 5,000-20,000 (Amos)(3)
April 28 5,000(4)
May 1 26,500 (MacDonald)(5)
May 12 25,000-50,000 (Crone)(6)

10,000-50,000 (Chiang)(6)

36,000 (Wereley)(6)

May 27 12,000-25,000(7)
June 10 20,000-40,000(8)
June 15 35,000-60,000(9)
August 2 53,000-62,000(10)

A report by the National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling found that “early official flow estimates would have been more accurate if the government had either enlisted greater in-house scientific expertise, or enlisted outside scientific expertise by making available the data on which government estimates were based.”

Is it political interference in science?

Maybe. From the initial days of the oil spill, independent scientists had significantly higher estimates than official government estimates. When newer data became available utilizing better methodologies, the government did not utilize the information and instead chose to maintain initial estimates. However, once Department of Energy Secretary, Stephen Chu became involved with the estimates, the methods rapidly began to parallel the estimates of independent scientists.

What is the best way to ensure scientific integrity?

It is important to increase the transparency of the science that is used for decision-making. When science is a critical element of federal decision-making, it is important to have a more public discussion about methodologies and uncertainties.


1. DOI, National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling. The Amount and Fate of the Oil. Staff Working Paper No. 3. October 15, 2010.   2. Oil Spill Response Unified Command. Update 8. April 25, 2010.   3. Amos J. Gulf Oil Spill Rate Must Be Much Higher Than Stated – 6 Million Gallons So Far? Sky Truth Blog. April 27, 2010.   4. NOAA. Oil Rate Estimate. April 28, 2010.   5. McDonald I. Gulf Oil Spill – New Spill Calculation. Sky Truth Blog. May 1, 2010.   6. McDonald I, Amos J, Crone T, Wereley S. The Measure of a Disaster. May 21, 2010   7. DOI, National Incident Command’s Flow Rate Technical Group. Preliminary Best Estimate Of Oil Flowing from BP Oil Well. May 27, 2010.   8. DOI, National Incident Command’s Flow Rate Technical Group. Press Briefing by National Incident Commander. June 11, 2010.   9. DOI, National Incident Command’s Flow Rate Technical Group. U.S. Scientific Team Draws on New Data, Multiple Scientific Methodologies to Reach Updated Estimate of Oil Flows from BPs Well. June 15, 2010.   10. DOI, National Incident Command’s Flow Rate Technical Group. U.S. Scientific Teams Refine Estimates of Oil Flow from BPs Well Prior to Capping. August 2, 2010.


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