Come January 20, President-elect Donald Trump will start carrying out his agenda. How does he expect to turn his promises into policy? Do his plans make sense? If not, what should he do? Finally, given the political realities of Washington, what is most likely to happen? This is part of a series of editorials that try to answer these questions.

What he says he will do:

Trump promises to pull the United States from last year’s Paris climate accord, which committed countries to reducing their greenhouse gas emissions, including a 26 per cent US reduction by 2025. There are procedural hurdles that stand in the way of a quick withdrawal; Trump could settle for simply not enforcing America’s commitments, which would amount to the same thing.

Does that make sense?

Certainly, if you believe global warming is a Chinese hoax. If you think the overwhelming majority of scientists may know what they are talking about, or if you have noticed that every year is warmer than the last, leaving the Paris deal looks more like a dangerous brake on the effort to cut global emissions at a time when the world can scarcely afford it. The consequences of ignoring established science could literally end the world. No responsible leader, in public service or private enterprise, can ignore data and information and expect to stay in his or her job.

What he ought to do:

Withdrawing from the deal is a solution in search of a problem. The American commitment in Paris is imminently achievable — even without President Barack Obama’s carbon regulations for power plants, which Trump promises to scrap, too. If he wanted to improve on the Paris deal, Trump could tell Congress to pass a carbon tax, coupled with a tariff on imports from countries that do not impose a tax of their own. That would take care of other countries freeloading off the US.

The most likely outcome:

Trump seems likely to make good on his promise. Less clear is what that means for the Paris deal. China has its own reasons for cutting emissions, and it may try to burnish its reputation by assuming America’s leadership role. Other countries, including India, may use US withdrawal as a reason to pull back themselves — or not, considering their vulnerability to climate change. At a minimum, an American withdrawal will not help matters.