The United States announced the most aggressive climate-change measures in its history Monday, a move that promptly triggered speculation about a potential ripple effect in other countries, including Canada.

The regulations released by the Obama administration would chop carbon emissions from U.S. power plants by 30 per cent by 2030, the majority of those cuts coming by the end of this decade.

The reductions are the equivalent of more than half the total carbon emissions in all of Canada.

They would take the U.S. a large step toward actually achieving the target it shares with Canada of 17 per cent greenhouse-gas reductions by 2020, and would single-handedly gobble up about one-third of the Americans’ objective.

Powerful economic trends are also playing in the U.S.’s favour.

American coal plants, the country’s biggest polluter, are already being supplanted by increasingly abundant, cheap and lower-emitting natural gas — while in Canada, the highest-polluting sector, oil and gas, is still on the rise.

Four years after Congress stalled a cap-and-trade plan, the announcement is the clearest example yet of President Barack Obama using executive authority to bulldoze his way past a hostile legislature.

To put the scope of Monday’s announcement in context, consider that the measures announced Monday have a potential impact hundreds of times larger than what’s at stake in the headline-grabbing debate over the Alberta-to-Texas Keystone XL pipeline.

“This is something that is important for all of us,” Obama said on a conference call where he cast the issue as not only central to his legacy, but to the legacy of entire generations.

“As parents, as grandparents, as citizens, as folks who care about the health of our families — (we) also want to make sure that future generations are able to enjoy this beautiful blue ball in the middle of the space that we’re a part of.”

Obama brushed off warnings that the measure could cost billions and kill thousands of jobs. That barrage of lamentations came not only from his Republican opponents, and their allied organizations like the U.S. Chamber of Commerce, but also from more centrist members of Obama’s own party.

The president described those warnings as a broken record, similar to those uttered whenever the U.S. has curbed air pollutants.

The issue will now be contested on multiple battlefields.

The first test will be political, in this fall’s congressional elections. Democrats close to the White House have released polls that suggest the issue can be a political winner for them, and that climate action is especially popular with women and growing voter groups — young people and Latinos.

Then there are the inevitable lawsuits. The administration believes it’s protected by a 2007 Supreme Court decision that gave it all the power it needs to regulate carbon emissions.

Finally, the U.S. has a new bargaining position to take into the next global climate talks in Peru in December.

There were no signs Monday of the announcement altering the course of events in Canada, beyond a gentle diplomatic nudge from Bruce Heyman, the newly appointed U.S. ambassador to Canada.

“We need to continue that work together moving toward a low-carbon future, with alternative energy choices, greater energy efficiency, and sustainable extraction of our oil and gas reserves,” Heyman said in prepared remarks he delivered Monday night in Ottawa.

“Newfound energy abundance should not distract us from the need to improve efficiency and combat climate change.”

When asked to comment on the U.S. measures, the Canadian government patted itself on the back.

Environment Minister Leona Aglukkaq issued a statement expressing satisfaction that the U.S. was joining Canada, which regulated its own electricity sector two years ago: “We are pleased that there will now be pan-continental regulations for this sector,” she said.

But comparing electricity sectors in the two countries is like comparing apples and oranges.

A big difference is that power plants cause nearly 40 per cent of U.S. emissions. In Canada, the sector was responsible for less than 13 per cent of emissions in 2011 — or 90 megatonnes out of 702 produced in the country, according to Environment Canada.

The leading emitter in Canada is oil and gas, and there’s nothing to suggest regulations for that sector are imminent. Aglukkaq said Canada would want to work on oil-and-gas regulations if the U.S. did too. The integration of the two economies required a joint approach, she added.

The opposition rolled its collective eyeballs at Canada’s response.

“It’s a total load of baloney,” NDP environment critic Megan Leslie said in an interview.

“If you take it seriously, you tackle your largest emitter…. The apples-to-apples comparison with Canada is the oil-and-gas sector.”

Liberal Leader Justin Trudeau, for his part, said the government’s attitude on the environment isn’t doing the economy any favours.

“If we do not demonstrate to the world that we as a country are serious about the environment, we will find it harder and harder to export our resources to global markets,” he said in a statement.

By way of comparison to Monday’s announcement, the Keystone pipeline has produced ample decibel levels of debate — but far fewer megatonnes.

In terms of carbon emissions, it would create somewhere between 1.3 to 27.4 megatonnes per year, according to a recent State Department environmental study. That estimate is wildly disputed: even within the State Department report itself, there’s a suggestion Keystone would actually reduce emissions compared to trains, while the report also estimates that its oil would produce up to 168 megatonnes per year over its life cycle.

According to projections released Monday by the administration, the power-regulations could reduce carbon emissions up to 555 megatonnes of carbon per year by 2030. The target will now be turned over to the states, which will have to issue individual plans between 2016-2018.