CAMBRIDGE, Mass. — With less than two weeks left in his term and some of the country’s top climate researchers in the audience, outgoing Secretary of State John Kerry placed his faith in science and industry in a speech at MIT on Monday, calling for a “real accounting” of the human cost of fossil fuels.

“At the end of our day, leaders can only do so much,” Kerry said. “We are relying on institutions like MIT and the private sector to get it done, because government won’t get it done.”

It was a shift in tone from Kerry’s remarks at COP22 in Marrakesh in November, which celebrated government leadership as a shell-shocked international community struggled to process climate denier Donald Trump’s narrow victory in the US presidential election just days earlier.

Trump will be inaugurated Jan. 20, and the Obama administration is working feverishly to lock in a legacy of pushing the world toward green energy sources while adding new environmental protections in the US.

One of Kerry’s signature diplomatic efforts, the historic signing of the Paris Agreement at COP21 in 2015, is expected to come under attack early in Trump’s tenure along with a number of Obama’s executive orders protecting air, land and sea. If confirmed by Congress, ExxonMobil CEO Rex Tillerson will replace Kerry as secretary of state. Trump’s Cabinet nominees represent a formidable force of climate deniers and friends of the fossil fuel industry.

“The times are harder than they have been,” Kerry said, the familiar waters of the Charles River flowing in the distance behind him. “I know the clock is ticking. I intend to keep involved in the public discourse. I guarantee you because I‘ve been doing it all my life that I will not stop speaking out about the issues that matter to me, and I know to you too.”

Echoing American leaders on climate change from President Obama to former vice president Al Gore to California Gov. Jerry Brown, Kerry continued to argue for the inevitability of global shift from burning fossil fuels to powering the planet on green energy. The question is, can the shift occur in time to stave off the worst effects of global warming?

“We face a strange combination of doubters and people making a lot of money off of today’s paradigm,” Kerry said. “Powerful forces invested in the status quo are working against change. We are in a race against time.”

Last year a Barclays energy analyst predicted that the fossil fuel industry risks losing $33 trillion in revenue over the next 25 years if companies “leave oil, natural gas and coal in the ground.”

Emerging economies like China, India and Brazil have seized upon the opportunity to invest billions of dollars into green energy, squinting to see a sustainable future through a toxic fog of fossil fuel emissions as their populations surge. Experts predict that civilization will depend on an “energy mix” of fossil fuels and renewables for decades to come. It is the balance of this mix which will determine how quickly the Earth warms and how dramatically human existence is disrupted.

“No nation will do well if it sits on the sidelines, choking on the fumes generated by obsolete technologies,” Kerry said.

With trillions more dollars and the fate of the planet on the line, Kerry delivered a line of optimism in what for many in the audience was his farewell address as secretary.

“Never before has the elimination of such a significant threat actually presented such a significant opportunity,” he said. “By and large, we know exactly what needs to be achieved.”

After leaving Foggy Bottom, he said, “citizen Kerry” plans to continue his work on climate change and to “keep faith with the revolutionary spirit that is the heart of this country.”

“I intend to keep involved in the public discourse,” said Kerry, who served Massachusetts as an assistant district attorney, lieutenant governor and six-term senator before President Obama nominated him to become secretary of state in January 2013.

“I guarantee you because I‘ve been doing it all my life that I will not stop speaking out about the issues that matter to me,” Kerry continued, garnering a round of applause from the hometown audience.

Kerry is still constrained by diplomatic norms, but has promised to speak openly after Donald Trump’s inauguration. On Monday, the secretary stopped short of criticizing Trump directly, but expressed hope that the presidency would change the president-elect’s approach to climate policy.

“As we know, there is going to be someone new in the Oval Office,” he said. “I can tell you that the view from the campaign trail is very different than the view from the office.”

With Boston Mayor Martin Walsh sitting in the front row, Kerry also touted the US-China climate summit scheduled for later this year, though no date has been announced. As climate change forecasting models demonstrate massive potential losses along New England’s coast in the years to come (among many other affected areas), local leaders will continue to play leading roles across the US.

“I know a lot of people are worried about what’s going to happen with the incoming administration, the fact is that mayors across the country, as well as governors, are working on this,” Kerry said.

Seeking allies in different sectors, the secretary promised to be more available after Inauguration Day.

“I wish I could take questions,” Kerry said in concluding his remarks and heading to a symposium on green jobs. “But in two weeks, there will be plenty of time for that.”