I remember the night in the autumn of 2012 when the first institution in the U.S. publicly committed to divest from fossil fuel. I was with a group of other climate activists in a big theater in Portland, Maine, halfway through a monthlong road show with rallies in cities across the country, and the president of tiny Unity College in the state’s rural interior announced to the crowd that his trustees had just voted to rid their endowment of coal, gas and oil stocks. We cheered like crazy.

On Tuesday, a little less than a week before the start of the United Nations climate conference in Glasgow, activists announced that the fossil fuel divestment campaign has reached new heights. Endowments, portfolios and pension funds worth just shy of $40 trillion have now committed to full or partial abstinence from coal, gas and oil stocks. For comparison’s sake, that’s larger than the gross domestic product of the United States and China combined.

It’s gone far beyond Unity College. Institutions such as Oxford and Cambridge (and more than half the public universities in the United Kingdom) have committed to divest; so have the University of California and the University of Michigan. Most of the Ivies are on board now, as are Catholic powerhouses like Georgetown; in the last couple of months, places as diverse as Harvard, Loyola University Chicago and Oregon’s Reed College have joined in.

My own employer, Middlebury College, agreed to divest in 2019, following a six-year campaign by students and faculty. But many schools have yet to act. The very first college to face divestment demands — Swarthmore, in Pennsylvania — has yet to make the commitment, and the same is true of plenty of others who should know better (Yale and Princeton, say).

And by this point, divestment has spread way beyond colleges and universities. Enormous pension funds serving New York City and state employees have announced that they will sell stocks; earlier this year, the Maine legislature ordered the state’s retirement fund to divest; and just last month, Quebec’s big pension fund joined the tide. We’ve seen entire religious groups — the Episcopalians, the Unitarian Universalists, the U.S. Lutherans — join in the call; the pope has become an outspoken proponent (and many high-profile Catholic institutions have announced they will divest). Mayors of big cities have pledged their support, including Los Angeles, New York, Berlin and London. And an entire country, even: Ireland has announced it will divest its public funds.

And some of the most historically important investors in the world have joined in too: A Rockefeller charity, the heirs to the first great oil fortune, divested early. Just last week, the Ford Foundation got in on the action, adding a great automotive fortune to the tally. This month also saw the first big bank — France’s Banque Postale — announce that it would stop lending to fossil fuel companies before the decade was out.

Since most people don’t have oil wells or coal mines in their backyards, divestment is a way to let a lot of people in on the climate fight, because they have a link to a pension fund, mutual fund, endowment or other pot of money. When we began the divestment campaign, our immediate goal was, as we put it, to “take away the social license” of Big Oil: It was a vehicle to let people know the essential truth about the fossil fuel industry, which is that its oil, gas and coal reserves held five times as much carbon as scientists said we could safely burn. Later this week, the heads of the big oil companies will testify before Congress about whether their companies misled the public about global warming and sought to stymie action on the problem.

The movement has grown so large that it’s now also testing the ability of some companies to raise capital. As early as 2017, Peabody was listing divestment as a major concern; by the next year, Shell was warning shareholders that the campaign could have a “material adverse effect on the price of our securities and our ability to access equity capital markets.”

Early divestment adopters have been handsomely rewarded; over the last five years, the market has gone up at an annual rate of 16 percent, but the oil and gas sector has fallen at an annual rate of 3 percent. Now many investors are putting their money into clean energy, where returns have risen by an annual rate of 22 percent over the same period. And one other sweet result: It was largely alumni of college divestment fights who formed the Sunrise Movement, a group of young climate activists, and championed the proposed Green New Deal; this has been a training ground for activists around the world.

This campaign still has a lot of work to do. Huge fights are underway in the teachers’ pension funds for New York and California; for financial giants like T.I.A.A., which maintains retirement accounts for educators and many others; and pretty much anywhere else where money and morality coincide. Yes, other people buy stocks when institutions divest, but, as The Times pointed out recently, it’s private equity funds that have invested at least $1.1 trillion into the energy sector since 2010, overwhelmingly in fossil fuels, trying to make a short-term killing.

The battle to wind down the fossil fuel industry proceeds on two tracks: the political (where this week may or may not see action on big climate legislation from Congress) and the financial. Those tracks cross regularly — the influence of money in politics is clear on energy legislation — and when we can weaken the biggest opponents of climate action, everything gets easier. Divestment has helped rub much of the shine off what was once the planet’s dominant industry. If money talks, $40 trillion makes a lot of noise.

Perhaps the first serious shadow to fall on the oil age came in the winter of 1969, after a blowout on a well, six miles off the coast of Santa Barbara. At least two million gallons of crude coated beaches and killed everything, from gulls to sea lions, and the resulting uproar fuelled the first Earth Day, in 1970, and also the first broad environmental laws in the United States, which were soon copied around the world.

Half a century later, oil has again coated the beaches of Southern California, this time from a ruptured pipeline near Newport Beach. Fortunately, the quantities aren’t as large—current estimates are some hundred thousand gallons—but beaches have been shut to millions of people, and a wetland conservancy that is a refuge for dozens of bird species may take decades to recover. (And the inability of the oil industry to monitor its equipment is maddening—the damage may have been caused as long as a year ago by an anchor hitting the pipe.) The response is less shock than resignation, since we’ve seen so many of these debacles in the past fifty years, including the Exxon Valdez spill and the BP spill in the Gulf of Mexico. But there’s a difference this time: the spill comes as the oil industry heads into a terminal decline, its reputation wrecked and its power starting to wane. Responding to a call from indigenous groups, environmentalists from around the country are descending on Washington, D.C., this week for a series of “People vs. Fossil Fuels” civil-disobedience actions outside the White House, Congress, and the Army Corps of Engineers; for the moment they’re being arrested, but in the long run they clearly have momentum on their side. The only questions now are how long the industry can hang on and how much more damage it will do.

As events of the past few weeks have made clear, long-term investors are running away from the fossil-fuel sector. So far, institutions have divested nearly fifteen trillion dollars’ worth of portfolios and endowments away from fossil fuels. Last month, Harvard announced that it will wind down its remaining investments. Other prestigious parts of the establishment followed. The MacArthur Foundation announced that it would move its $8.2-billion endowment away from fossil fuels. On Friday, Dartmouth University joined the list, leaving only three of eight Ivies—Yale, Princeton, and Penn—to make the move. More will follow; divestment campaigners are planning big announcements for October 26th, in the lead-up to the 2021 Glasgow climate summit. (I have helped with the divestment effort.) Those talks can’t come soon enough, because the existential climate threat gets more apparent every day. Earlier this month, Genoa saw the heaviest rainfall ever measured in Europe, with around thirty-five inches—a typical yearly total for Seattle—falling in a single day. The rain came down twice as fast as September’s epic and terrifying deluge in New York.

Meanwhile, scientists have been zeroing in on the health hazards that fossil fuels pose to humans. As Sammy Roth points out in the Los Angeles Times, the economic benefits of getting off fossil fuels in the U.S. alone, “in terms of lives saved, hospital visits avoided and workdays not lost due to illness or deaths—would exceed $700 billion per year, higher than published estimates of the costs of weaning the economy off fossil fuels.” And a spate of data has been making it increasingly clear that there’s no long-term cost to leaving fossil fuels behind. Indeed, the latest research indicates that the faster you transition the more money you save. If the first famous California oil spill was a Greek tragedy fated by our dependence on fossil fuels, this most recent one—and the endless daily spill of carbon and smoke into the air—is a tragedy of a different, more venal kind.

Along the way, there will be transitional bumps of all kinds. At the moment, the price of oil is rising, because there’s a worldwide commodity boom and the pandemic depressed drilling. But if that helps oil companies for a quarter, or three, it hurts it in the long term: gas is about $3.25 a gallon right now, and that means that anyone thinking about, say, a new pickup truck has one more reason to choose the electric Ford F-150, with the car company already taking preorders for spring delivery. Got solar panels on your roof and an E.V. in the garage? You’re your own filling station, insulated from oil’s decline.

Really, the only asset the fossil-fuel industry has left is political clout, and that, too, is waning. Joe Biden, in the last debate of the 2020 campaign, said that it was time to “transition away from the oil industry,” and his Build Back Better plan does precisely that, with serious money behind a push to use penalties and tax credits to spur utilities toward clean energy. He’s got forty-eight Democratic senators—representing well more than half of the American population—lined up behind it. Only the oil industry’s death grip on the G.O.P. and the craven opportunism of West Virginia’s Joe Manchin and Arizona’s Kyrsten Sinema hold back the future. On Friday, Sinema (who began her political life in the misbegotten adventure of Ralph Nader’s 2000 Green Party run) enigmatically demanded that a hundred billion dollars be cut from the climate funding in the Build Back Better bill.

That political cloud and the delay it can produce present an enormous challenge; if we haven’t cut emissions in half by 2030, climatologists warn, we’ll miss our chance to hit the climate targets we set in Paris, with all the attendant chaos that will follow. On that long list of things at stake in the fight, the sands of California are perhaps not the most vital, but they make clear the possible outcomes. Those beaches—and Hollywood’s depiction of them—came to help define the image of an idyll. If the sea level keeps rising, however, two-thirds of Southern California’s beaches could vanish. And if we keep pumping oil, some of it will inevitably keep spilling. On the other hand, solar spills hit Santa Barbara two hundred and eighty-three days in an average year. That could be the future.