A group of 100 leading Canadian and U.S. scientists has issued an urgent call for a moratorium on new oilsands development and listed 10 reasons why no more projects should be permitted.

"I believe we have a duty to speak up," said Mark Jaccard, an energy economist at B.C.'s Simon Fraser University who spent more than a year drafting a letter to make sure it was scientifically sound.

Jaccard was a co-author of a 2014 essay in a scientific journal that made a similar argument. But the current letter, released Wednesday, represents a much wider cross-section.

Economists, biologists, climatologists and political scientists have all signed the text, which has been sent to Prime Minister Stephen Harper and all members of Parliament. The signatories include 12 fellows of the Royal Society of Canada, 22 members of the US National Academy and a Nobel Prize winner.

They are careful to include in their warning all high-carbon energy sources, including coal and other types of unconventional oil, but it's focused on the oilsands.

"No new oilsands or related infrastructure projects should proceed unless consistent with an implemented plan to rapidly reduce carbon pollution, safeguard biodiversity, protect human health and respect treaty rights," the letter says.

Greg Stringham of the Canadian Association of Petroleum Producers said science will make the industry sustainable.

"There are thousands of other scientists working across the world on behalf of industry and government to ensure that these oilsands are developed responsibly," he said.

Jaccard said he was struck by the number of natural scientists who asked to sign. More and more of them, he said, are seeing climate change affect their work.

Jaccard remembers one scientist who studied British Columbia's pine trees, decimated by a pine beetle expansion made worse by warming temperatures.

"This little scientist studying pine beetles and the foot of Godzilla called climate change comes down on top of it," Jaccard recalled.

"He said, 'I feel silly. Why am I just studying this thing and not trying to help humanity do something?"'

David Schindler, a University of Alberta ecologist, agreed.

"Everyone in this group really sees what climate change is starting to do to our ecosystems and the potential for harming society in major ways."

The harm will be more than environmental, suggested David Keith, who teaches both physics and public policy at Harvard.

"The world is going to gradually decarbonize and the decisions will not be driven from Alberta," he said.

"The deeper we get into a commitment to these large projects, the better off we are in the very short term, but the worse off we are in the long term. We'll be worse off economically when there are real restrictions on carbon emissions."

Climate change is a challenge for every aspect of society, said Thomas Homer-Dixon, who leads the Centre for International Governance Innovation at Ontario's University of Waterloo.

"There's an enormous number of social science disciplines that are involved in this problem. We're dealing with social phenomena rather than natural phenomena, and they're all wrapped up in this problem of climate change and the impact of climate change."

Industry knows things are changing, said Stringham.

"We fully recognize the energy mix is changing. It's just not one at the expense of the other -- let them compete with their technologies and their environmental impact."

The answer isn't a moratorium, but even more spending on research to mitigate the industry's impacts, he said.

"It's applying technology in an accelerated fashion that's going to be the answer to the future of where oilsands goes."

Wednesday's letter is an example of natural and social scientists feeling compelled to share knowledge that increasingly alarms them, said Homer-Dixon.

"If we just keep it within our academic journals and papers, we're not doing the broader society any favours. The situation is urgent and the information and knowledge that we have needs to be part of the conversation."