Official oil sands emissions estimates may be understating the problem

An aerial study by Environment Canada suggests that the carbon pollution by oil operations in northern Alberta's oil sands, already the largest single carbon polluter in the country, may be severely understated.
Analyzing air samples above four major oil sands operations, the study concluded that greenhouse gas emissions were an average of one-third higher per barrel of oil produced than the mines were reporting during the same period, with one offender (SynCrude, if we are naming names) showing about two-and-a-quarter more than reported.
This may have been just a snap-shot, as the mines in question are complaining, but it is indicative of a problem in the "bottom-up" method of reporting used for everything from reporting national emissions to calculating carbon taxes (bottom-up calculations rely on some ground measurement and a lot of mathematical modelling).
It also questions the wisdom of setting the fox in charge of the hen coop, so to speak, by relying on self-reporting by the oil companies. I don't know what kind of auditing procedures have been established, but clearly they are not sufficient, and perhaps some combination of bottom-up and top-down emissions estimates is needed.