Since the early 1990s, the consensus view in the climate science community has been that if the world is going to escape the most catastrophic consequences of climate change, it needs to keep the average global temperature from rising more than 2 degrees Celsius, compared with preindustrial levels. A few years ago, the Presidential Climate Action Project issued a report in which it estimated that to meet that goal, global carbon dioxide emissions would need to be reduced by 60 percent by 2050 — and the industrialized world would need to reduce its emissions by 80 percent.

This would seem, at first glance, an impossible task. Until, that is, you meet a man named David Crane. He is the chief executive of NRG Energy, the largest publicly traded independent power producer in the country. When he took over a decade ago, NRG was just emerging from bankruptcy. Today, it is a Fortune 250 company, with 135 power plants capable of generating 53,000 megawatts of power.

NRG, Crane told an audience at the Aspen Ideas Festival this summer, is the country’s fourth-largest polluter. “We emit 60 or 70 million tons of carbon into the atmosphere each year,” he said, mainly because a third of its power is generated by coal-fired plants. “I’m not apologetic about that because, right now, owning those plants and operating those plants are critical to keeping the lights on in the United States.”

But then he quickly added, “We have to move away from that.” And he has, reducing the company’s carbon footprint by 40 percent in the decade that he’s run the company. And, on Thursday, as The Times reported, he committed NRG to reducing its carbon emissions by 50 percent by 2030 and 90 percent by 2050.