BY CHRIS ARSENAULT
TORONTO - Up to 450 billion tonnes of greenhouse gases would be kept out of the atmosphere if the U.S. government stopped leasing federal lands to fossil fuel companies, according to a study released on Wednesday.

The government currently allows energy companies to lease federal lands for drilling, and environmental groups say if the practice is not halted, the United States will be unable to meet its obligations to combat climate change.

The oil, coal and gas under lands owned by the federal government constitute up to half of the potential emissions from all remaining U.S. fossil fuels, according to the analysis by the consultancy EcoShift on behalf of the Center for Biological Diversity and Friends of the Earth environmental groups.

"Our government has already leased more public fossil fuels then can be safely burned," Marissa Knodel, a campaigner with Friends of the Earth, said in a statement.

"Each new lease puts us farther down the path toward climate catastrophe, and is a direct contradiction to the president's pledge to attack the climate crisis head-on."

The potential greenhouse gas emissions released if all of the energy reserves buried under federal lands were burned is equivalent to a quarter of the total international emissions that can be released if the world is to limit global warming to below 2 degrees, the study said.

United Nations scientists say that rises above 2 degrees would cause a climate disaster.

U.S. government agencies do not track the amount of greenhouse gas emissions coming from federal leasing of land to energy companies, environmentalists said.

The study is thought to be the first attempt to measure the pollution potential of fossil fuel reserves on U.S. government land, the study's author said.