AMNA NAWAZ: California is suing big oil.

It's the latest lawsuit targeting fossil fuel companies over their role in climate change.

And it comes during Climate Week, one of the largest annual events designed to focus on the problem and in tandem with the meeting of the U.N. General Assembly.

William Brangham has the details on this case.

WILLIAM BRANGHAM: California claims the five biggest oil and gas companies, ExxonMobil, Shell, Chevron, ConocoPhillips and BP, as well as the American Petroleum Institute, knew that using their products led to climate change, but then spent decades misleading the public.

The lawsuit says extreme weather fueled by climate change has caused billions of dollars in damages in the state, and these companies should pay for some of that damage.

Joining us now is California Attorney General Rob Bonta.

Attorney General, thank you so much for being here.

You're arguing that these companies knew all along that burning coal and oil and gas would exacerbate climate change, and there's, as you cite in your suit, plenty of documentary evidence that they knew that.

And you're arguing that they weren't forthcoming about that knowledge.

What are you alleging that their silence actually meant?

ROB BONTA (D), California Attorney General: They were actually very active in pushing forward and advancing the deception.

They knew 50, 60, 70 years ago that their fossil fuels that they were selling created climate change.

They predicted with terrifying certainty where we would be today, with extreme weather events, with dries getting drier and hots getting hotter and wets getting wetter,.

Their internal memos, their industry-commissioned studies, their speeches internally to one another all said this.

And they were very active in their deception.

What do I mean?

They worked with front groups.

They supported and funded front groups with great climate-supportive names like Global Climate Coalition to undermine the climate science that they knew was inaccurate, that they knew the actual truth.

Internally, they acknowledged that they talked about it, and they pushed out into the public science that would dilute that truth, that would undermine it, that would cast doubt, so they could profit to the tune of billions and billions of dollars over many, many years, just profiting $200 billion last year.

So they also knew about clean energy pathways forward.

They knew about carbon sequestration.

They knew about things that could have put our planet on a better pathway.

But they chose to ignore those, to push those down and push and lift up fossil fuels, all for profit.

So they lied to the people of California.

So we're asking them to put billions of dollars into an abatement fund to mitigate future environmental damage and to provide for resiliency and adaptation going forward.

WILLIAM BRANGHAM: Let's say that they had been more frank about their understanding of climate change.

What would you have wanted those companies back then to have done differently?

ROB BONTA: Be truthful, very simple.

Don't lie, don't deceive, don't hide from the public clean energy pathways forward, and don't hide from the public the existential threat that fossil fuels created in terms of climate change and extreme weather and damage to the environment.

With full knowledge, the people could make choices about their future, our planet's future, our children's and grandchildren's future.

Perhaps choices would have been different, like doubling down and investing on clean energy and phasing out of fossil fuel.

Who knows?

But they should not have lied.

They should have told the truth.

They affirmatively lied to the people of California time and time again with their editorials that they produced.

Their marketing arm, the industry association, the American Petroleum Institute was very involved with this, with the faux science that they put out, all meant to make people believe something different than what the actual truth was, that we were on a pathway towards disaster as a state and, frankly, as a nation and a world.

WILLIAM BRANGHAM: The American Petroleum Institute put out a statement about your suit, saying in part -- quote -- "This ongoing coordinated campaign to wage meritless politicized lawsuits against a foundational American industry and its workers is nothing more than a distraction.

Climate policy is for Congress to debate and decide, not the court system."

What do you make of that argument, that, in fact, it is incumbent upon senators, governors, presidents to determine policy, energy policy, and that going after a private company is inappropriate?

ROB BONTA: That entire statement by the American Petroleum Institute is entirely in character with the statements that they have made over the last number of decades.

That statement is a distraction.

That statement is not true.

That statement wants you to focus on other things besides the actual truth.

There will be and there is an entirely separate and independent pathway for action in this space that is pointed out by the American Petroleum Institute.

That is something different than what we're doing.

It's for Congress and legislative bodies to make policy about climate change.

And they are.

The Biden administration has been a great leader in this space.

But our lane, a separate lane, is the lane of legal accountability in court.

The state of California is suing big oil in state court for the damage that they have caused.

This is not a policy lawsuit.

This is a straight-up legal cause of action that has remedies in court.

Cases like this have been brought before against the tobacco industry, against the lead paint industry, against the opioid industry, when entire industries hurt people time and time again in great numbers and at great scale and lie about it.

This is not new.

WILLIAM BRANGHAM: Governor Newsom has said that the damage caused by this deception, as he puts it, by these oil companies, is incalculable.

So, how do you calculate the role that a given oil company might have contributed to a drought, a wildfire, a storm in California?

How do you do that?

ROB BONTA: We think it's in the range of tens of billions to hundreds of billions of dollars in ongoing damage going forward.

That's the sort of big picture estimate.

We will need experts, scientists to look at attribution of different damage to the different defendants and looking at causation to determine the specifics.

And so that will take time.

We will get more evidence and information through the course of the lawsuit and make those determinations throughout the course of the lawsuit down the road.

WILLIAM BRANGHAM: All right, Attorney General Rob Bonta of the state of California, thank you so much for being here.

ROB BONTA: Thanks for having me.