France’s new environment minister, Nicolas Hulot, does not mince words when it comes to the possible consequences of Donald Trump pulling the United States out of the Paris climate accord.

Such an act, Hulot said in March, when Trump first signaled that he might withdraw from the agreement to limit carbon emissions, would be “a veritable middle finger to our children,” and could even expose the American president one day to charges of “crimes against humanity.”

Worst of all, Hulot told French television, was the danger that Trump’s action could encourage his fellow climate skeptic, Vladimir Putin, to ignore the restrictions on industrial emissions. Together the two leaders could create, Hulot warned, “an axis of mass destruction between two great powers,” with catastrophic consequences for the planet.

Hulot, who was an environmental activist before joining President Emmanuel Macron’s new government, expressed his concern after Trump ordered the E.P.A. to rescind restrictions on carbon emissions and Putin said that the melting of Arctic ice was most likely a natural process that Russia should take advantage of, not try to stop.

Putin’s remarks, which horrified Hulot, were made during a forum on the future of the Arctic, days after Trump moved ahead with his campaign promise to lift regulations on coal, oil and gas producers imposed by former President Barack Obama.

Speaking in the Russian Arctic city of Arkhangelsk, Putin told the American business channel CNBC that it was “impossible” to stop the warming of the planet, which was more likely caused by “some global cycles on Earth or even of planetary cycles,” than man-made factors like industrial emissions. Climate skeptics, like Trump and E.P.A. head Scott Pruitt, Putin added, “may not be at all silly.”