He loves to cite his favorite new statistic: a recent report by the International Energy Agency that found that last year, global gross domestic product grew 3 percent, while carbon dioxide emissions flatlined. Historically, economic growth has paralleled the growth in fossil fuel emissions.

“The data show it’s possible to grow the economy without growing pollution,” Mr. Deese said with visible excitement.

Known for pacing while he talks on the telephone and sometimes going without shoes in the office, Mr. Deese appears at his most animated when plunging headlong into the wonkery of an issue.

“This is somebody whose greatest joy is that swift arc up the learning curve,” said Gene Sperling, the president’s former national economics adviser. “He has both this amazing policy I.Q. that he can bring to any issue as well as the humility to reach out and find and listen to every expert on the planet on that issue.”

Mr. Deese is now on a very steep learning curve. In January, he flew to New Delhi with the president and was in the room as Mr. Obama urged Prime Minister Narendra Modi of India to cut his nation’s greenhouse gas emissions.

In March, Mr. Deese was in Kentucky, where anger against Mr. Obama’s climate change plan runs deep. The plan requires states to cut carbon emissions, effectively forcing them to change their energy supply from fossil fuels to renewable sources — a tough sell in a coal-mining state like Kentucky. There Mr. Deese appeared with Governor Steven L. Beshear, a Democrat, at an event promoting a federal program to help coal communities and then spoke with him for an hour afterward about the climate change plan.

But Mr. Deese has hardly assuaged the anger over the plan, particularly among Republicans who see it as either a war on coal or a vast overreach through the E.P.A. regulations of Mr. Obama’s executive authority. If put in place over the next year, the plan could drive major changes in the nation’s economy in the next decade, from shutting down coal-fired power plants, spurring renewable electricity generation and forcing automakers to build fleets of all-electric vehicles.