Updated at 12:37 p.m. Nov. 5

John Kerry struck out with an optimistic tone about the U.N. climate summit on Thursday.

"I guarantee you, we are going to come out of Glasgow with a level of ambition that is going to surprise people," the special presidential envoy for climate told host Jim Braude on Greater Boston.

The 2021 Conference of the Parties, known as COP26, kicked off on Sunday, bringing together world leaders to strike deals on combatting climate change. Former Secretary of State Kerry spoke enthusiastically about the market shifts that are greening the global economy and commitments from countries that previously haven't been “at the table.” But Dr. Vanessa Kerry, director of the Global Public Policy and Social Change program at Harvard Medical School and CEO of Seed Global Health, pointed out that global health — which is threatened by the changing climate through its impact on food, water, sanitation and shelter — has been largely left off of the agenda.

In a wide-ranging interview, Sec. Kerry and Dr. Kerry briefed GBH on the talks so far, covering everything from former President Donald Trump's climate change denialism to health equity to misinformation in the United States.

Sec. Kerry was confident in President Joe Biden’s ability to pass environmental legislation, asserting that there is international faith in the country’s efforts.

“I think people here know what he [Biden] is fighting for. And I believe the president is going to get this legislation through,” Sec. Kerry said. “I don't know when the moment will be, but I believe that Congress will pass this at some point in time ... and the world will see it.”

He said the Democratic Party’s slowness to adapt climate legislation amid political discord has not dampened the United States’ influence at the summit.

“Believe me, nobody's raised it with me. Not one conversation has anybody said to me, 'Oh, you guys can't do it, look at what's going on [in Congress].' Hasn't happened,” he said. “But would it be helpful? You bet. It would be wonderful to walk into a meeting, and say, 'Look at what we're doing,' and use [new legislation] as leverage.”

Sec. Kerry also praised a new level of engagement from countries such as Saudi Arabia and South Africa, highlighting efforts to meet the target he initially sought with the 2015 Paris Climate Accords: capping global warming to a 1.5-degree Celsius increase.

"About 65% of global GDP is now working on adopted plans to be able to keep 1.5 degrees alive," Sec. Kerry said. "I'll tell you, six months ago, I wouldn't have believed that was possible, but it's happening, and we have more to come in the next ten days."

And for those who do make commitments, technological advances help keep up public accountability, Sec. Kerry said. He recalled a Washington Post investigation that worked off of satellite data to show a massive methane leak in a Russian republic. In the past, countries might simply understate emissions or deny problems, but that's no longer possible in the same way.

“You know the old saying, you can run but you can't hide? ... When people say, 'We're gonna be net zero by 2050,' you're gonna be able to zero in on any big corporation and actually trace out their entire supply chain,” he said.

Sec. Kerry added that countries are sensitive to public pressure. "They don't want to come and be the black sheep, or the entity that's not getting the job done.”

But the efforts to combat climate change are not simply at the whims of politicians, either, he recognized. When pressed on the potential for Americans to elect a president uniniterested in tamping down emissions, Sec. Kerry said that the movement is, at least in part, out of the government’s hands. General Motors, for instance, has committed to selling exclusively electric vehicles by 2035.

"No politican would be able to stop what the marketplace is now doing,” Sec. Kerry said. “Trillions of dollars have been held out now to become part of this transition. ... That investment level, in three years, will be so powerful across the world that, I'm telling you, no politician in any country would have the ability to reverse that.”

Dr. Kerry praised the “aspirational” tone of the summit. But, she added, there are significant inequities that hold back countries’ abilities to participate in such major shifts.

"For countries that are looking to join the economies of the world today, to have so much of their population at risk from either climate change or from health, it's an impossible thing to overcome without a major influx of resources,” said Dr. Kerry, who is also Sec. Kerry’s daughter. “The resources exist, the science exists, the technology exists — the only thing that is missing is political will.”

But she said the mood at COP26 is shifting, and leaders are stepping forward in an effort to “meet this moment.”

When it comes to climate change deniers in the United States, Dr. Kerry put the responsibilty on systems of misinformation. She said she gets the opportunity to teach when patients get sick from smog, smoke and asthma attacks. And as the health impacts of climate change become more prominent, more people come to realize the source of illness, or can learn about it from physicians.

“We have a system right now that allows people to live in bubbles of communities, online and elsewhere, where they can really shelter themselves with a certain amount of information,” she said. “Until we can figure out how to get through the misinformation pandemic we also face, it's very difficult to change minds and make those connections.”

But Sec. Kerry added that climate change is increasingly getting harder to ignore.

"Mother Nature has been sending some pretty powerful messages to everybody,” he said. “The floods in the central part of the country, the farms that have been wiped out. The forests of California, the extraordinary water problem in the western part of the country, around Nevada, Colorado, California, Arizona. The heat — the level of heat — the drought, the mudslides. You add it all up, and I'm telling you, there are a hell of a lot more believers today than there ever were before.”

Making one last case for implementing climate legislation, Sec. Kerry said that steps toward combatting climate change are simply a “no-brainer.”

“The majority of our country absolutely wants us to deal with the climate crisis,” he said. “It will result in a cleaner, healthier and safer United States and world. No question about it.

“I voted thousands of times as a United States Senator,” he went on. “Sometimes you agonized over what the impact and pluses and minuses were for a tax code or for individual citizens, and there's always that balance. This is a no-brainer! This is not a hard choice. This is the easiest thing you can possibly choose to vote on. ... You could have a complete collapse of agriculture in Africa, and then you'll have tens of millions of people knocking on the door to get into other countries. That's a security threat. That's why I say we'll be safer if we deal with it. And every single analysis shows it is far, far more expensive if you wait and just suffer the damage than it is to invest in these new technologies, make this transition, create a clean energy future with all of the jobs that that will entail and the benefits that come with it."

This story was updated to include Dr. Vanessa Kerry's title as CEO of Seed Global Health.