INTERVIEW-NASA's Hansen concerned about Canada's oil sands

By Deborah Zabarenko, Environment Correspondent

WASHINGTON, Feb 18 (Reuters) - Canada's oil sands are an environmental "wild card," NASA's James Hansen said in an interview before President Barack Obama's trip to Ottawa, where energy and climate change will be on the agenda.

As director of the U.S. space agency's Goddard Institute for Space Studies in New York City, with a focus on climate change, Hansen has long opposed the burning of oil, gas and coal for their contribution to global warming.

And he really objects to the burning of fuels gleaned from tar shale and tar sands in western Canada.

"If we burn all the conventional fuels -- oil, gas and coal -- we would be heading the planet to eventually an ice-free state," Hansen said in an interview on Tuesday, two days before Obama's scheduled visit to Canada, the first foreign trip of his presidency.

"This unconventional fossil fuel is a total wild card on top of that," Hansen said. "You just can't do it, that's what politicians and international leaders have got to understand. You can't exploit tar shale and tar sands without pushing things way beyond the limit. They're just too carbon intensive."

For this reason, Obama's discussion on Thursday with Canadian Prime Minister Stephen Harper is a "a really important meeting," Hansen said.

There are financial and national security benefits to refining fuels from oil sands in the Canadian province of Alberta, which holds some 173 billion barrels, the largest oil deposits outside the Middle East.

But getting them out of the ground is complicated and costly, in some cases requiring operators to scrape off as much as 100 feet (30.48 metres) of soil before reaching deposits layered with sand, clay and water.