Scientists offer conflicting BP oil spill cleanup figures

Figures on the amount of oil still in the Gulf of Mexico have baffled the public since the BP well was capped. The numbers vary so wildly that Gulf coast residents are not sure if they should be alarmed or feel reassured.

Some 784 million litres of crude oil escaped into the ocean since April, and now scientists seem at odds over how much, or how little, of it is still there.

THE FIGURES, ACCORDING TO NOAA 4.9 billion barrels (784 million litres) leaked into the Gulf of Mexico. Of this total: 26% still present in the ocean or coastline 17% collected at the bottom of the ocean 5% burned 3% skimmed off (collected on the surface of the ocean) 8% dispersed by chemicals 16% naturally dispersed 25% evaporated or dissolved Source: National Oceanic and Atmospheric Administration (NOAA)

Figures presented in an August 4th report by the US National Oceanic and Atmospheric Administration (NOAA) suggests that three-quarters of the spill has been eliminated.

But experts at the University of Georgia rained on those sunny estimates on August 16th, publishing their own study that says 79 percent of the oil remains in the water.

On the margins of error

But for some experts, the huge gap in the reports is not impossible to reconcile, or perhaps proof of the researchers’ incompetence. “You have to consider the margins of error in both studies,” says Christophe Rousseau of the French-based Centre for Research and Testing on Accidental Water Pollution (Cedre). “Considering the significant margins [of error], the two studies are not as contradictory as they might seem.”

“The figures are not incorrect, but they are estimates,” continues Rousseau. “The researchers at NOAA and the University of Georgia, who are both capable scientists and even renowned in this field, should have stressed the fact they are working with estimates.”

According to Rousseau, the two groups were not working with the same amounts of leaked oil; another explanation for the discrepancy. The University of Georgia study, Rousseau claims, did not account for oil recovered at the ocean bottom, some 17 percent of the total leaked oil.

Fishermen: "I haven't seen a thing." (The Huffington Post) Oil hidden under 1.8 million gallons of dispersant (Examiner) Georgia researchers say as much as 80 percent of the oil remains in the Gulf (AP)

Lessons from Erika

The debates surrounding the cleanup efforts in the Gulf of Mexico oil spill are reminiscent of those in France after the 1999 Erika oil tanker disaster.

But there are important differences between the two events, Rousseau says. The oil slick on the Brittany coast was heavy, refined oil that spilled close to shore. The images of the environmental disaster were beamed into people’s homes and shocked a nation.

“But the closer the leakage is to the coast, the easier it is to recover the oil,” says Rousseau. “In the case of BP, the light crude is very difficult to recover. The leak occurred off the coast and at great depths, so the percentage of oil that will remain in the ocean will be much higher.”

Like other oil spills, the associated images will stick in the public’s memory far longer than figures or statistics. To combat this, US President Barack Obama did not hesitate to invite the media to join him for a dip in Florida waters.

Unfortunately for the US administration, the New Orleans daily the Times-Picayune recently reported that thousands of dead fish have been found at the mouth of the Mississippi river. Authorities have announced they will investigate a possible link with the oil spill.