CALGARY - Two new government-funded reports suggest that oilsands oil doesn't create that many more greenhouse gas emissions than other conventional crude sources when everything is taken into consideration.

The reports, released Thursday, say that oil from oilsands creates from 10 per cent to 45 per cent more greenhouse gas than other oil imported into the U.S. when everything from exploration to burning in a car engine is taken into account.

But environmentalists counter the studies only confirm that the oilsands generate the most carbon-intensive fuel around. They add the reports downplay how much more greenhouse gas is emitted as oilsands oil is produced.

"When you look on the full cycle like that, it diminishes the apparent differences that are caused by the source of the oil," said Dan Woynillowicz of the environmental think-tank Pembina Institute.

The reports examined a wide variety of crude oils that are commonly imported into the U.S. and some from American sources.

It found, when all direct emissions from well to tailpipe are considered, oilsands oil creates at best 10 per cent more greenhouse gas than conventional crude. Depending on the source of the crude, that figure could go as high as 45 per cent higher.

The reports also point out that carbon emissions from conventional oil are rising, as resource pools get harder and harder to exploit. On the other hand, oilsands emissions are declining on a per-barrel basis as the industry improves and becomes more efficient.

The reports were an attempt to put some hard, specific numbers around the climate change impact of various fuel sources as the U.S. country works toward policies on greenhouse gas emissions.

"Numbers were being assumed for conventional crudes and we decided to do this study to ensure we understood the comparison," said Eddy Isaacs of the Alberta Energy Research Institute, the government body that funded the studies.

"We were hoping we would put the facts on the table so that (as) policy-makers are considering how they set up the low-carbon fuel standards, at least they know that this is a complex business to measure them."

The report will come in handy, said Rachel Bouska, spokeswoman for Alberta Advanced Education and Technology.

"Some U.S. policy-makers and lawmakers have considered Alberta's oilsands dirty oil," she said. "We have the facts and the data to support the fact that it's only about 10 per cent higher."

"Alberta's getting a bad rap."

At least one American wasn't convinced.

"I think they're underestimating the U.S. audience," said Susan Casey-Lefkowitz of the Washington-based Natural Resources Defence Council.

"(Americans) are going to see (the reports) indeed confirm that tarsands oil has very high greenhouse gas emissions. It's still the dirtiest."

Woynillowicz pointed out that a gallon of gas has the same carbon footprint whether it was refined from sweet Saudi Arabian crude or oilsands bitumen. Including those emissions in the overall figure, from well to tailpipe, dilutes the fact that so much more carbon is emitted during oilsands production.

Comparing well-to-tank emissions is much clearer way of comparing fuel sources, Woynillowicz said.

"It's more meaningful if your objective is to understand how greenhouse gas emission intensity varies from one source to another."

Isaacs acknowledges that producing oilsands oil creates more greenhouse gases.

"We are high on our produced oils," he said.

However, he said that well-to-tailpipe is the common standard for comparing life cycle emissions of differing fuel sources.

"That's what other people have been doing."