CAMBRIDGE, Mass.—Secretary of State John Kerry used his final official speech on climate change to urge the world to keep ramping up climate action and accelerating the transition to clean energy.

"We are in a race against time," said Kerry to a crowd of about 270 people at the Massachusetts Institute of Technology on Monday. Glaciers are already melting, sea levels are rising faster than ever and there are more intense storms. "Unless we take the steps necessary to change the course that our planet is on, the impacts we've already seen will pale in comparison to what we will witness in the years to come."

Kerry has delivered dozens of iterations of this speech, an impassioned defense of climate action, since he became secretary of state in February 2013. But this one took on new urgency with the impending inauguration of Donald Trump, who has nominated Rex Tillerson, the chairman and chief executive officer of ExxonMobil, to succeed Kerry.

Kerry expressed confidence that the United States would meet all its promised climate targets, partly because the transition to the clean energy economy was already underway. But he also warned that the shift must come faster to avert the worst climate impacts.

"The question we face today is whether we can accelerate that transition," he said, "whether we will excite the necessary investments to fully unlock the clean energy market in the future in time to avoid the catastrophe we will inevitably see if we allow the greenhouse gases to keep going up and up and up."

"Now, this really shouldn't be a tough call," he added, "but...we face resistance of a strange combination of doubters and people making a lot of money off today's paradigm."

What's often left out of the climate conversation, Kerry said, is that "the elimination of such a significant threat actually present[s] such an extraordinary level of opportunity. That's what's so confounding to me as we get in this debate."

Kerry called on research universities to help ensure progress on climate action. "We are relying on ingenuity of MIT and institutions like it, along with the private sector, to get this job done," he said. "Because the government can't get this job done and won't get it done."

But it's unclear how much federal money places like MIT will be receiving, or for what kind of energy research, under Trump. The Obama administration, along with a score of other nations, have pledged a huge escalation of global research addressing the climate crisis.

As the nation's chief diplomat, Kerry helped broker the Paris climate agreement and more recently a global agreement to phase out potent greenhouse gases used in refrigeration. His commitment to the issue extends back a quarter century to his early days as a U.S. senator from Massachusetts. He was an ally of Al Gore and other lawmakers at the start of the global struggle to confront climate change.

Although Kerry would not say what he plans to do after leaving office in two weeks, he told the crowd: "I guarantee you, because I've been doing it my whole life, I will not stop speaking out about the issues that matter most to me and I expect you too."