Implementing greener energy use not only means a reduction in carbon dioxide in the atmosphere, but more jobs and economic development, Kerry said during a speech at the Massachusetts Institute of Technology in Cambridge, Mass. A million dollars spent retrofitting equipment for clean energy creates more jobs than a similar investment in fossil fuels, he claimed.

The clean energy sector will create, rather than eliminate jobs, in Kerry’s view, because it requires research, retrofitting and installation work by businesses, universities, and the government. That’s in stark contrast to the jobs—from truck drivers to paralegals—that will be lost due to advances in artificial intelligence and robotics.

Kerry, who joked that he is about to become one of “the most visible unemployed people in America,” has signaled that he will continue to work to promote clean renewable energy when he leaves office on Jan. 20 after President-elect Donald Trump’s inauguration. Working as President Barack Obama’s point person, Kerry promoted the Paris Agreement geared to cutting global greenhouse gas emissions that was signed by the U.S. and 120 other nations last year.

But President-elect Trump has expressed mixed views about climate change and the Paris accord, so there is a lot of uncertainty about what action his administration will take. Trump’s nominee to succeed Kerry at the State Department is Rex Tillerson, just stepped down as chief executive and chairman of Exxon Mobil (XOM) after spending 40 years at the energy giant. Critics worry that his long ties with the oil business bode ill for renewable energy.

But Kerry seemed cautiously optimistic on this front. He wouldn’t speculate on the incoming administration’s climate policies: “But I have learned that some issues look a lot different when you’re in office than when you’re on the campaign trail.”

In his remarks, Kerry also expressed confidence that the U.S. will meet all emissions targets already set, not because of any government mandates, but because of market forces.

“The curve is bending towards sustainable energy worldwide,” he noted. “The question is not whether we’ll transition to low-carbon energy, the question is whether we can accelerate that transition, he said. That is key is more investments to spur more clean energy research and development to make a real difference in the climate trends before it’s too late.

Many climate change deniers are motivated by entrenched financial interests in the continued use of coal and other fossil fuels, which contribute to greenhouse gasses in the atmosphere. Climate deniers may acknowledge changes to the weather, but cast doubt on whether human actions, like burning fossil fuel, contribute to those changes.

Get Data Sheet, Fortune’s technology newsletter.

There could be ways to mitigate existing damage, he acknowledged. “I just talked to President Obama about ways to suck CO2 out of the atmosphere, but by and large, we already know what has to happen, which is a transition from dirty, outdated energy sources to cleaner more efficient sources.”

Such sources include solar and wind energy but also biomass, organic material that can include forest debris, agricultural, food waste, and manure. Nuclear energy, traditionally a sore point among environmentalists because of the danger of nuclear accidents, fallout, and storage of spent fuel, should also be part of the mix, he said.

“I remember the intensity of the nuclear debate back in the 1970s on the first Earth Day, and I was on the other side then but given our challenges and improvements to the technology, go for it,” Kerry noted. “It’s zero emissions.”

For more on clean energy, watch Fortune’s video:

Clean energy should not be a partisan issue in his view, since U.S. military leaders, the intelligence community, and the medical establishment all point to the toll of rising sea levels and dirty air. The aggregate costs to governments and businesses worldwide of building sea walls, pumping stations, and dams in cities and military bases, and treating cases of environmentally induced asthma, emphysema, and black lung, should all be factored into the total cost of burning fossil fuels, he said.

“What’s the worst that can happen if climate deniers are wrong and we do this work? There will be fewer people in the hospitals, more people working in clean energy, people living longer, and less dependency on foreign oil,” he said.

“And what’s the worst that will happen if climate deniers are wrong and we don’t do this work? The planet dies.”