Global warming.
It seems to be a hot topic with politicians lately.
It certainly sparked some controversy at last week's Green Living Show after former U.S. Vice-President Al Gore blasted Ottawa's greenhouse action plan calling it a "complete and total fraud" and "misleading" to Canadians in his message he delivered to a sold-out crowd.
Opposition leaders echoed Gore's comments and also took some jabs at the Conservatives' plan.
All this backlash prompted Canada's Premiers and territorial leaders to tackle the issue once again at the Council of the Federation meeting Tuesday.
Agreeing on the need to combat climate change was the easy part for provincial leaders, but reaching a consensus on how to get there appeared to be trickier.
Ontario Premier Dalton McGuinty said, "Some people say that if you drive really hard [on greenhouse gas emissions] you'll plunge us into a period of economic darkness, and others say that we don't need to do anything.
"Canadians understand this. We do need to do something."
The Tories' environmental plan is under attack for not setting any hard limits for emissions as required under the Kyoto protocol.
However, Harper's government has warned that meeting Kyoto targets, as Canada previously agreed it would do, would plunge the country into a recession.
McGuinty agreed that cutting pollution could drive up energy costs and have other economic repercussions, at least in the near term, but said cleaning up the air is imperative.
"There's going to be at least some modest inconvenience associated with that and I think Canadians are ready for that," he said.
"They expect us to assume our full responsibility as global citizens."
Saskatchewan Premier Lorne Calvert offered only qualified endorsement of the idea, saying Canada needs to focus its energy on cutting overall greenhouse gas emissions.
Alberta has already expressed resistance to the notion of setting hard caps for emissions.
British Columbia Premier Gordon Campbell said his province is already involved in a regional emissions-trading initiative with American states such as Washington and Oregon.
Other provinces are welcome to join in, but B.C. plans to press ahead regardless, Campbell said.
"I can tell you I'm not waiting for unanimity from the provinces or from anyone else," Campbell said just before the meeting started. "We believe a cap and trade system is critical."
Both McGuinty and Campbell insisted that emissions-trading, which means bigger polluters can buy credits from smaller ones to avoid penalties for exceeding their limits, is key to reducing greenhouse gases.
The all-day meeting held at the Royal York Hotel came less than a week after Ottawa announced its new green plan.