Until Prime Minister Stephen Harper lost his job in Canada's elections on Monday, he was part of a dwindling group of world leaders who've actively worked against climate progress on an international stage. With the Liberal Party's Justin Trudeau becoming the next prime minister, a significant roadblock to an international climate agreement in Paris in December is now clear.

Harper, the outgoing leader of the Conservative Party, may not have been as vocally opposed to climate action as, say, U.S. Republicans, but he’s repeatedly tried to undermine international progress in more subtle ways. He was one-half of the world’s most powerful anti-climate duo, which broke apart only last month when his partner—ex-Australia prime minister Tony Abbott—lost his job in the Liberals' party leadership elections. He withdrew Canada from the Kyoto Treaty in 2011, just as major polluters (including the U.S. and China) began to rethink their approach to fossil fuels. He and Abbott planned to complicate negotiations on limiting global greenhouse gas emissions, and Harper congratulated his peer on his progress in scuttling domestic climate initiatives. “You’ve used this international platform to encourage our counterparts in the major economies and beyond to boost economic growth, to lower taxes when possible and to eliminate harmful ones, most notably the job-killing carbon tax,” Harper told Abbott when the latter visited Canada in summer of 2014. In the last year, he's snubbed United Nations climate summits and his officials reportedly tried to weaken language from an official G7 text that pledged serious long-term cuts to greenhouse gas emissions. 

As Canada's elections drew near, Harper took half-hearted steps to pretend Canada was not so out-of-step as the rest of the world on climate change as it seemed, pledging funds for green finance and proposing cuts to carbon emissions. The government committed to 30 percent cuts by 2030, but said nothing about how it would address the tar sands, the fastest growing source of the nation’s emissions. Nothing in Harper's record, meanwhile, suggested he had any intention of meeting this goal. Canada already will miss its 2020 climate target, even though the United States has proved it's possible to meet the same goal. “In climate policy, the Canadian government has done virtually nothing to keep its 2020 and 2050 emission reduction promises,” wrote Mark Jaccard, a professor with Simon Fraser University's School of Resource and Environmental Management, in an October report card on the country’s climate policies. He gave Harper’s administration a “failing grade.”

On a domestic level, Harper's offered Canada’s oil and tar sands industry his unconditional support. He went beyond simply advocating for the Keystone XL pipeline, secretly devoting $30 million of taxpayer dollars to public advocacy. His administration has stifled climate scientists’ ability to talk to press, and is accused of muzzling environmental nonprofits by ordering extensive audits.

But as Harper has learned, tying his fate to the oil industry also has its risks. Canada’s tar sands industry has faltered as oil prices collapse, and Harper's own fortunes plunged along with it. 

Trudeau has both the opportunity and challenge to repair Canada’s outcast status after nine years of conservative power. Trudeau will be better on the environment, but far from an environmentalist's dream PM: He supports the Keystone XL pipeline, and has not made clear how he plans to reconcile the tar sands industry’s growth and the need to cut Canada’s emissions—two priorities that are at odds with each other. Trudeau has said, "I am committed to showing up with all premiers to take on the target we need which is to prevent the two degrees of warming that scientists across the world are looking at as catastrophic," but has offered few specifics. During the election, his campaign was full of contradictions, like accusing Harper of turning “the oil sands into a scapegoat around the world for climate change and he’s put a big target on our oil sands.”

There are still a number of reasons to be encouraged that the Liberals can turn around Canada’s climate policy. Paris will be just the start of it. Within 90 days of Paris, Trudeau has promised to call on the provinces' leaders to help come up with a plan for climate action, to begin to undo some of Harper’s damage. These reforms could include ending fossil fuel subsidies, putting a price on carbon, and evaluating the environmental footprint before signing off on pipeline proposals. And expect more details from Trudeau himself soon: His first appearance on the global stage will likely be in Paris later this year.

Correction: An earlier version of this article stated that ex-Prime Minister Tony Abbott lost his position in an Australian election. He was ousted by Liberals in a party leadership contest.