Ben Nelms/Bloomberg via Getty Images Flames shoot from a flare at the Suncor Energy Inc. Millennium upgrader plant in this aerial photograph taken above the oilsands near Fort McMurray, Alta., on Sept. 10, 2018. A new study suggests carbon dioxide emissions linked to Alberta's oilsands could be much higher than previous estimations.

New federal research suggests greenhouse gas emissions from Alberta's oilsands may be significantly higher than industry reports.

In a study published Tuesday, Environment Canada scientists say four major oilsands mines are releasing an average of about one-third more carbon dioxide per barrel of oil than they report — a crucial number used for everything from determining national emissions levels to calculating carbon tax.

Lead author John Liggio and his colleagues analyzed air monitoring samples captured in a series of flights above the four sites during the course of a month in 2013.

Suncor's facility was 13 per cent over its estimated emissions.

But the emissions intensity of Canadian Natural Resources Ltd.'s Horizon and Jackpine mines averaged 37 per cent higher than they reported. And Syncrude's Mildred Lake mine was emitting two-and-a-quarter times more of the climate change-causing gas than it told Ottawa's pollutant registry.

"We find a pretty significant difference,'' said Liggio, whose paper is published in Nature Communications.

First study of its kind

Until now, all carbon dioxide emission estimates from the oilsands have been based on a combination of some ground measurement and a great deal of mathematical modelling — so-called bottom-up estimation.

The new study is the first to use actual field measurements taken from aerial overflights, or top-down measurements.

The findings of industry underestimation echo those of a previous Alberta study, which found methane emissions from heavy oil facilities were much higher than thought. They also agree with many other studies that have compared bottom-up to top-down.

"There's still more work to be done,'' Liggio said. "But I will say there are many, many studies using top-down approaches which have also shown that top-down (measurements) are generally higher.''

The measurements in Liggio's paper include emissions from mining, processing, upgrading and tailings ponds.

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