All in all, the government will return about 1.7 billion Canadian dollars to businesses and families this year, more than the 1.2 billion dollars it expects to collect though the carbon tax, which amounts to roughly 5 percent of the province’s total tax revenue.

According to the World Bank, about 12 percent of the world’s global emissions of greenhouse gases are subject to a carbon price — either a tax or, more commonly, a levy under a regime of cap and trade like that in California and Europe, in which permits to emit are auctioned among companies.

With few exceptions, British Columbia’s tax is the steepest and broadest in existence. While that sets British Columbia apart as a leader on the cutting edge, it is also part of its problem. For the policy to work best, it needs the rest of the world to catch up.

Local leaders now recognize that they probably have to do more. Carbon emissions started rising again after the province froze the tax at 30 Canadian dollars in 2012. An advisory panel to the Ministry of the Environment recently laid out the problem: British Columbia is missing its goal of cutting greenhouse gas emissions by a third from 2007 to 2020. On its current path, the province will also miss its target of an 80 percent reduction by 2050.

This is not entirely British Columbia’s fault. True, the tax might have been too low. Spending some of the money on green initiatives might have curbed emissions faster. But its experiment has battled a harsh headwind: a collapse in the prices of oil and gasoline.

Look at it this way. A study by Michael Greenstone and Thomas Covert of the University of Chicago and Professor Knittel concluded that at current battery prices, for an electric vehicle to be cheaper to run than a gas-power car, oil would have to cost $350 a barrel. Last year, it averaged $50. To make up the difference would require a carbon tax of $700 a ton of carbon dioxide.

Nobody in British Columbia is talking about going that far. But to hit its long-term target, the advisory panel concluded that the tax must start increasing again in 2018, at a rate of 10 Canadian dollars a ton a year, perhaps all the way to midcentury.