Newly elected Canadian Prime Minister Justin Trudeau and President Obama are expected to sign onto a joint climate change strategy during Trudeau’s upcoming visit to Washington. The agreement, to be approved this week, will likely touch on automotive fuel standards and include measures to spur the adoption of electric vehicles.

This is notable for two reasons. First, crude oil is Canada’s largest export, and the United States is Canada’s biggest customer. That Trudeau is working with Obama to cut petroleum consumption on both sides of the border, even as plummeting oil prices spur a downturn in Canada’s economy, is nothing short of remarkable.

Second, a bilateral agreement to cut carbon pollution would almost certainly not have been possible even a year ago. For the last decade, Trudeau’s predecessor, Stephen Harper, undermined climate action seemingly at every turn, genuflecting to Canada’s most powerful and politically influential industry — oil. Since Trudeau’s Liberal Party swept to power in October, Canada has seen a stunning about-face on climate policy.

During his tenure, Harper made no attempts to regulate carbon pollution through cap-and-trade or a carbon tax. He muzzled scientists, cut research funding, targeted environmental groups, and secretly committed government money to advocating for the export of tar sands oil. To environmentalists, Harper was a villain. Climate Action Network Europe ranked Canada among Russia, Iran, and Saudi Arabia in its 2015 Climate Change Performance Index, a rating of countries’ climate policies.

On the international stage, Harper didn’t fare much better. In 2011, Canada became the first signatory of the Kyoto Protocol to formally withdraw from the agreement, pulling out after it became clear it would not meet its carbon-cutting targets. In the lead-up to the Paris Climate Agreement, Canada pledged to limit carbon pollution, but it committed to emissions reductions that were markedly less ambitious than those of the United States or the European Union.

Where Canada has made progress on climate change, it has largely happened at the provincial level. In 2008, British Columbia instated a carbon tax. Last year, Ontario and Quebec began emissions trading with California. And, more recently, historically conservative Alberta passed a carbon tax and set a cap on carbon pollution from oil sands.

Alberta’s climate policy marks a striking reversal for the oil-rich province, and comes in the wake of a historic election. In May, the liberal New Democratic Party of Alberta defeated the ruling conservative party, which had controlled the provincial government for more than four decades. The change of power heralded a new era of climate policy in Canada and the beginning of the end for Stephen Harper.

That Harper ultimately lost his job to Trudeau likely added insult to injury. In 1980, Justin Trudeau’s father, then-Prime Minister Pierre Trudeau, installed an energy program that suppressed the price of oil, dealing a blow to Alberta’s flagship industry. Harper, who was then living in the Western province and working for Imperial Oil, blamed the initiative for thrusting Alberta into recession. According to his biographer, William Johnson, the experience sparked Harper’s political awakening and fueled his contempt for Pierre Trudeau.

Now, after ten years at the helm, Harper must watch the younger Trudeau dismantle his pro-oil agenda. As a candidate, Justin Trudeau promised to end subsidies for fossil fuel companies and invest in clean energy technology. As Prime Minister, he attended the Paris climate negotiations and, more recently, he proposed a federal minimum carbon price as part of a national climate change plan.

While Trudeau publicly defended Keystone XL, he criticized Harper for his preoccupation with the pipeline. Obama’s rejection of Keystone XL may have come as something of as blessing for the new prime minister, allowing him to abandon his half-hearted support of the project and focus on his climate agenda. Since taking office, Trudeau has proposed expanding the environmental review process for oil and gas pipelines.

While Canadian-U.S. relations were strained under Harper, owing in part to the battle over Keystone XL, President Obama says he now sees Canada as a “strong partner” on climate.

“Things are happening in a way we haven’t seen in a decade,” Erin Flanagan, Director of Federal Policy at the Pembina Institute, told ThinkProgress last week. “The two administrations are quite aligned on what they want to see happen.”

As the United States and Canada work to meet their commitments under the Paris Accord, they may find ample room for cooperation on climate and energy — cutting black carbon pollution in the Arctic and fostering the spread of clean energy. The forthcoming agreement on represents just one possible point of collaboration.

“To fight climate change, we’re all on this together,” tweeted Trudeau at the Paris climate negotiations. “Canada is back.”

Jeremy Deaton and Mina Lee write for Nexus Media, a syndicated news service covering climate, energy, policy, art and culture.Nexus Media News