OTTAWA -- An abridged timeline of carbon pricing developments in Canada:

April 24, 2007: British Columbia joins five western U.S. states in the Western Climate Initiative, a market-based climate action group.

March 8, 2007: Alberta becomes first province to legislate greenhouse gas reductions from large industrial emitters by introducing a price on carbon through the "specified gas emitters regulation," which came into force July 1, 2007.

April 18, 2008: Quebec and Ontario formally join the Western Climate Initiative.

July 1, 2008: B.C. becomes first province to implement a carbon tax.

May 30, 2008: Conservative environment minister John Baird says, "Carbon trading and the establishment of a market price on carbon are key parts of our Turning the Corner plan."

Oct. 14, 2008: Conservative government wins federal minority mandate on platform that promised to "develop and implement a North American-wide cap-and-trade system for greenhouse gases and air pollution, with implementation to occur between 2012 and 2015."

Oct. 14, 2008: Liberal party suffers its worst defeat to that point in the party's history on a platform that promised to raise up to $15 billion in carbon taxes, offset by cuts to income taxes.

Nov. 19, 2008: Conservative speech from the throne promises, "We will work with the provincial governments and our partners to develop and implement a North America-wide cap-and-trade system for greenhouse gases and an effective international protocol for the post-2012 period."

June 10, 2009: Conservative environment minister Jim Prentice releases two draft documents he says "lay the foundation for the development of a carbon market across Canada .... It does so by establishing a price for carbon in Canada -- something that has never been done before in this country."

December 2009: Conservative government says it is "working in collaboration with the provinces and territories to develop a cap-and-trade system that will ultimately be aligned with the emerging cap and trade program in the United States."

May 2, 2011: Conservatives win majority government on platform that dropped promise of cap-and-trade system, while official Opposition NDP and third-place Liberals both included cap-and-trade systems in their platforms.

Jan. 1, 2013: Quebec formally starts operating within the Western Climate Initiative's cap-and-trade carbon market.

Nov. 12, 2013: Prime Minister Stephen Harper's parliamentary secretary issues a public statement: "Canada applauds the decision by Prime Minister Abbott to introduce legislation to repeal Australia's carbon tax. The Australian prime minister's decision will be noticed around the world and sends an important message."

Dec. 17, 2014: Harper tells CBC he would like to see Alberta's carbon tech fund model, which prices carbon, implemented across North America.

Jan. 14, 2015: Ontario government says it plans to introduce carbon pricing in 2015.

March 31, 2015: Harper tells House of Commons, "Canadians do not think we respond to fallen oil prices by hiking taxes on the energy industry. They do not think we respond to that by imposing carbon taxes on Canadians."

April 7, 2015: Release of "Turning the Corner: A Practical Approach to Reducing Canada's Greenhouse Gas Emissions," by Canada's Ecofiscal Commission, recommending provinces take lead on carbon pricing.