Many hours before the 1998 ice storm hit, Alain Bourque was tracking it from his Environment Canada office. As a meteorologist, he knew instinctively it was going to be devastating, and he warned as much.

Yet he could only watch helplessly as the storm approached and then quietly encased parts of Quebec and Ontario in ice, immobilizing the lives of millions of Canadians and causing millions in damage.

Bourque, a kind of prophet-scientist, had a similar experience tracking the effects of climate change.

"I still remember doing presentations on climate change in the 1990s and basically people were looking at me and saying, 'What is he telling us?'" Bourque said in an interview.

Fast forward nearly 20 years, near the end of the hottest year yet on record, and Bourque is sitting in a harshly lit hall in the heart of a suburban Paris exposition park that is hosting the world's biggest and most promising gathering on fighting climate change.

World leaders, including new Canadian Prime Minister Justin Trudeau, had opened the conference promising to help save the planet from catastrophic warming.

Within days, ministers from around the world would overcome bitter differences to sign on to a global agreement to reduce greenhouse emissions in an effort to limit the rising global temperature and avert more of its calamitous effects.

The so-called Paris Agreement, coming into effect in 2020, would aim to keep warming from rising above 2 C over pre-industrial levels, and aims in the long term to limit that to 1.5 C. It would do so by ensuring carbon emissions peak as soon as possible, and asking nations to set national targets for reducing emissions and improving them regularly.

Bourque, now one of the world's leading experts on climate change, had before the conference been invited to brief the new prime minister and premiers on the science behind climate change.

Environmentalists demonstrate near the Arc de Triomphe in Paris on Dec. 12 in Paris. Canadian scientist Alain Bourque says individuals can do much to decrease greenhouse gases, regardless of treaty details. (Pascal Rossignol/Reuters)

He is still stoic about the apparent buy-in on the part of world governments, and their willingness now to see the coming climate-change storm.

"For scientists, the Paris conference is more of a political process or a decision-making process," he told CBC News.

"The main objective really is to decrease greenhouse gases. Personally, I find that we probably rely too much on governments and treaties in order to do stuff.

"At the end of the day, I think it's all the individuals that need to decrease greenhouse gases and do the job."

They are prescient words. Because for all the promises made at the 21st meeting of the Conference of Parties, or COP21, and within the resulting deal, they mean nothing without buy-in from the businesses, industry, the private sector and ordinary people who will help put them into effect.

For all those like Bourque who have been yelling in the wilderness about climate change — like many among the thousands of scientists, activists, policy wonks and politicians who came to Paris — the fact nearly 200 countries signed on to one document underpinned by science they are acknowledging as indisputable is the kind of sweet vindication they hoped for but never imagined.

Bittersweet for May

It was, oddly, also an occasion for some regret.

"It's hellish to realize that we've procrastinated for decades, that the climate disasters that we're seeing now could have been avoided," says Green Party leader Elizabeth May, who was invited by Trudeau to attend as a member of the official Canadian delegation for the first time in years. In the Stephen Harper years, she had to come once as a member of the Afghanistan delegation in order to attend.

What helped bring the Paris deal together was buy-in from previously skeptical countries such as China and India, whose prime minister Narendra Modi is seen speaking at COP21 on Nov. 30. (Stephane Mahe/Reuters)

"It is an emotional and extremely powerful moment for me personally and for the world ... but it's not the end of the road.

"This treaty gives us the possibility of giving our grandkids a liveable world," she adds.

Of course, in the words of U.S. Secretary of State John Kerry after the deal was done, no country thought the deal was perfect, but with so many competing and incompatible demands, it was "exactly the way it should be."

What helped clinch it was buy-in from powerful but skeptical developing countries, namely China and India. Even Saudi Arabia — which had fought bitterly against the 1.5 C target and though unimaginably wealthy, demanded financing for new technology — backed the deal.

Like the political players, environmental organizations also saw it as "a start," but still had many issues with it, including its often imprecise language, or because it has no means of enforcement.

Still, there were some upsides.

"I think that what this gives us is an aspirational target and there is a global climate movement that is trying to hold governments to those promises," author and activist Naomi Klein told CBC News in an interview.

"It also sends a signal to the fossil fuel sector to the market that this industry is not going to be able to continue in this way forever. We're talking about a gradual phasing out of fossil fuels. So I think all of it contributes. But it's not enough."

Canada's low-carbon challenge

May and many others insist a deal would have probably been difficult to clinch had Canada's Harper and Australia's Tony Abbott — both deeply skeptical of the move to cut emissions, and both ousted recently — still been in power.

The sea change in Canada's attitude on climate change alone directly contributed to the deal coming together. A change that Bourque helped root in science in the course of a 25-minute briefing he gave Trudeau and premiers in November.

"Having a Canadian government that actually tried to raise the ambition of the global climate agreement made a difference in Paris," said Dale Marshall, national program manager at Environmental Defence.

But now, says Marshall, "Canada must act at home."

The international agreement could give Prime Minister Justin Trudeau and his cabinet occasion to be bold as they prepare to set, with the provinces, a Canadian emissions target. (Alain Jocard/AFP/Getty Images) With Canadian indigenous and labour groups, cities, and provinces in attendance, in many ways, the conference acted as a dress rehearsal for the new government as it prepares to sit down with the provinces in about 90 days to set a new national target for reducing emissions.

Emma Ruby-Sachs, acting Executive director of Avaaz, hopes the international momentum will give Trudeau and his cabinet occasion to be bold.

"They haven't yet taken the lead that I was hoping they would take in Paris ... So maybe when they get back home they can show that global leadership."

That, says Ruby-Sachs, must mean that private and public money should be moved out of the Alberta oilsands, for example, and that the economy must nurture innovation in renewable energy technology such as solar power.

Catherine McKenna, Canada's environment minister, acknowledged the agreement sends a clear message to the Canadian fossil fuel industry.

"The reality is we need to move to a low-carbon economy," she said Saturday following the agreement.

"I think it sends a signal to the market that this is the direction the world is going to take so take advantage of it."

It is what all countries must do to avoid the coming climate change storm, advises Bourque.

"There are already clear trends. It's going to amplify in the future so some of the hardest hit communities are saying, it's now. We need to act now.

"Because whether it's a Canadian or Chinese or someone in India emitting greenhouse gases, for the climate it doesn't change much. So we all need to do this."