The environmental news of the year — if not the decade — is the United Nations COP21 Climate Agreement reached in Paris on December 12, 2015. The 195 nations of the world reached an understanding in principle to hold global warming “well below 2°C” and to strive to limit the rise to 1.5°C. Elizabeth May, leader of Canada’s Green Party and a long-time attendee at such climate talks, called it “a masterful balancing act” between the ideal and practical. It may not be perfect but it’s something that can be accomplished.

Key parts of the agreement include a contribution from developed nations of $100 billion per year, beginning in 2020, to help developing and undeveloped nations adapt to a low-carbon future. These billions will translate into trillions in private investments in clean and renewable energies. Further, all nations are expected to reach peak greenhouse gas emissions “as soon as possible”, so that by 2050 carbon emissions will not exceed those being captured by “sinks” — essentially creating a carbon neutral planet. And finally, 5-year reviews will examine the progress of all nations toward their committed objectives.

This COP21 agreement couples with a November 2014 unilateral deal between China and the United States to cut their emissions. And adding to the shift in consciousness was a June decision by the G7 nations, the world’s largest economies, to become carbon-free by 2100. Also in June came Laudato Si, the encyclical by Pope Francis which gave profound moral authority to humanity’s obligation to cut carbon emissions.

In Canada, a change in government from Stephen Harper’s Conservatives to Justin Trudeau’s Liberals has literally revolutionized this country’s response to environmental issues generally and to climate change particularly. Instead of being negative and even obstructionist in international COP meetings, Canada has taken a position that is positive and helpful — even being asked to assume a facilitating role in negotiations. Unlike past COP conferences when delegates criticized and ridiculed Canada’s contributions — even suggesting it would be better for everyone if we had not come — we are now being welcomed with smiles and applause.

All these changes will reverberate throughout Canada. The new Liberal government will henceforth include carbon emissions as a considered element in all environmental assessments, including such projects as coal facilities, oil pipelines and LNG plants, thereby reducing the likelihood that such fossil fuel enterprises will proceed. The use and export of these carbon-rich resources will be seriously constrained by ambitious emission targets, periodic monitoring by the United Nations, and international censure for unmet commitments.

The international pressure to reverse global climate change is now immense. This pressure will be passed from the COP21 agreement to individual nations who will, in turn, pass it to their lower echelons of government. In Canada, the initiative taken by provinces, cities and municipalities to reduce emissions will now be met with encouragement instead of indifference. A spirit of co-operation will help Vancouver reach its goal of becoming the world’s greenest city. Alberta’s carbon tax and the cap-and-trade regulations of other provinces will be sanctioned. A moratorium on oil tankers plying BC’s coast and doubts about the province’s LNG projects now fit within a larger and wiser logic.

The world changed on December 12, 2015.