The back-to-back reduction was attributed to a drop in the amount of coal used to produce electricity, warmer winters leading to reduced fuel consumption for space heating, and less fossil fuel use in the oil refining industry. Emissions haven't fallen for consecutive years since modern record keeping started in 1990.
Emissions peaked in 2004 at 743 million tonnes, and the reduction since then has been the equivalent of taking about seven million cars off the road.
Although Ottawa has put in place a number of programs to cut Canada's releases, the reasons cited for the fall had little to do with federal action, and Environment Minister John Baird reacted cautiously to the numbers.
While greenhouse-gas emissions have decreased in 2006 for a number of reasons, we have to continue the fight against climate change, he said in a statement.
Canada's single largest program to reduce greenhouse-gas emissions is in Ontario, which has pledged to cut releases from coal-fired power plants by two-thirds below 2003 levels by 2011.
The drop still leaves Canada well behind its target for reducing greenhouse emissions under the Kyoto Protocol, which requires the country to cut its releases to below 1990 levels during the period from 2008 to 2012.
Emissions in 2006 were 22 per cent above the 1990 total and almost 30 per cent above Canada's Kyoto target of 558 megatonnes, giving Canada one of the poorer records in the industrialized world when it comes to reducing global warming pollution from the burning of fossil fuels.
Experts who follow trends in greenhouse-gas emissions expressed surprise at the drop. It is a surprise actually that for the second year in a row that there would be emission reductions, said John Drexhage, director of climate change and energy programs at the Winnipeg-based International Institute for Sustainable Development.