In April a group of oil companies—including BP, ExxonMobil, and Chevron—made a $4.3 billion bet off the coast of Azerbaijan, in the Caspian Sea. The companies approved a plan to expand deepwater drilling operations there, boosting oil production by as much as 100,000 barrels a day—taking advantage of “world-class assets,” in the words of one executive. But according to a recent analysis by the think tank Carbon Tracker, the Caspian Sea investment, along with a number of fossil fuel projects approved by major energy companies in 2018 totaling $50 billion, makes financial sense on one condition: if countries around the world fail to rein in carbon emissions enough to meet the goal of the 2015 Paris Agreement, which aims to limit the rise in average global temperature to well below 2 degrees Celsius above preindustrial levels. Many of those energy companies have voiced support for the climate accord in public, but in the private rooms where investment decisions are made, they are essentially wagering that it will fail.

It’s easy to feel pessimistic about the future of the international climate pact, with the task so ambitious and the stakes so high. The accord rests on voluntary commitments from countries to lower their emissions—a structure that the climate scientist Katharine Hayhoe has compared to a potluck dinner: Each nation brings a different dish, in the form of an emissions reduction plan, to the table, in the hope that the cumulative result will be a feast to save the planet. But when the Paris Agreement was signed in 2016, it became clear that the initial commitments made by individual countries to reduce their greenhouse gas emissions would send the world hurtling past 3°C degrees of warming. Today few of the world’s largest emitters are on track to hit even those targets. Meanwhile, this past July was the hottest month ever recorded. People in Iceland held a memorial for a mass of ice once called Okjökull, which lost its status as a glacier in 2014—the first due to climate change. In Alaska the water in the Kuskokwim River grew so warm that salmon appear to have died from heart attacks.

But the Paris Agreement is still in its infancy. To its defenders, one of its most important features is that it “was deliberately written to improve over time,” according to attorney Susan Biniaz, who was the State Department’s lead climate negotiator from 1989 through the end of the Obama administration. At its core, the agreement is less a plan than it is a process for countries to assess and update their individual commitments to climate action. Signatories are asked to present more ambitious targets for reducing their emissions every five years, with the next round of plans due at the end of 2020. To build momentum for this ratcheting up, world leaders will meet in New York City on September 23 for a Climate Action Summit, and UN Secretary General António Guterres has asked countries to arrive with “concrete, realistic plans” for strengthening their pledges over the next 14 months. This next stage in the Paris process presents a crucial test: Can countries reconcile their commitments with global goals?

A report released last year laid out just how tight the time line for action is. According to the UN’s Intergovernmental Panel on Climate Change, the world needs to decrease emissions roughly 45 percent from 2010 levels by 2030—in just 11 years—and get them to net zero by 2050 in order to limit warming to 1.5°C, a threshold that models indicate would be far easier to adapt to than 2°C or more of warming. “The summit is critically important as a galvanizer,” said David Waskow, the director of the World Resources Institute’s International Climate Initiative. “One can’t get where we need to go by 2050 in terms of decarbonization without this next decade being one of serious, aggressive action on climate. That’s the message that came from the IPCC’s report a year ago, and that’s the message leaders need to take to heart. If they don’t do that in the next 18 months, if they don’t put us on that pathway where we take significant action over the coming decade, the 2050 objectives will become incredibly difficult to achieve.”

One leader is expected to be conspicuously absent from the summit: Donald Trump. After he announced his intention to withdraw the United States from the Paris Agreement (which can’t officially happen until 2020, for procedural reasons), some observers worried that it would sap other countries’ ambitions. Instead, the US has largely been isolated—although State Department representatives continue to try to influence negotiations behind closed doors—as other countries move the process forward. “We know his position,” French President Emmanuel Macron said after Trump skipped a climate session at the G-7 meeting in August. “We did not have [an] objective to convince him to return.” The strategy seems to be to ignore Trump and hope that someone else is elected in 2020.

If the Democratic nominee wins the presidency next year, he or she will need to tackle climate change immediately to get the United States on track. The organization Climate Action Tracker considers the US “critically insufficient” in meeting the Paris targets, thanks in part to the Trump administration’s rollback of policies like the Clean Power Plan, the bedrock of the Obama administration’s Paris pledge. But aligning domestic policy with the 1.5°C temperature target would require action far more radical than simply undoing Trump’s work and restoring Barack Obama’s. So far, only a few Democratic candidates have laid out climate plans that acknowledge the speed and scale of what’s needed.

All the major candidates on the Democratic side have said they’d recommit the country to the Paris process, and all have embraced an ambitious long-term target in line with the agreement: reaching net zero carbon emissions by 2050. The fact that this target has become mainstream for Democrats obscures just how significant it is, as Vox’s David Roberts has written. Hitting it would require an unprecedented political and economic transformation, starting pretty much right now.

For that reason, what matters more than the 2050 target is what presidential candidates pledge to do in the next decade, said Leah Stokes, an assistant professor of climate politics at the University of California at Santa Barbara. “If you say, ‘Look, we’ve got to be doing this by 2030 so that we’re on track to doing things by 2050,’ you’re having to make harder choices that are not just ‘Hey, let’s have a more fuel efficient car—but it’s still a combustion engine,’” she said. The kinds of policies that the US would need to adopt to get on this trajectory are far more radical than raising fuel efficiency standards or imposing carbon taxes—both of which “are great,” Stokes continued, “but they do not drive technological innovation or deep decarbonization. They are really about efficiencies at the margins of a fossil-fuel-based system.”

Looking at commitments on this shorter time scale makes it easier to see differences in the candidates and their climate plans. Some, like former vice president Joe Biden and Minnesota Senator Amy Klobuchar, simply don’t have many concrete targets in the near term or specific plans for implementation. This is a long Democratic tradition, Roberts points out. Thanks to Republican obstructionism, Democrats have been able to embrace far-off goals while rarely having to commit to any aggressive, immediate action that might cost them political capital—the failed attempt to pass a cap-and-trade bill in 2009 being one exception.

Washington Governor Jay Inslee distinguished his candidacy by embracing specific, immediate action on policy change in his suite of climate plans, some of which have been adopted by Massachusetts Senator Elizabeth Warren. Inslee, who ended his presidential bid in August, argues that “vague promises or love letters to 2050 will not get the job done.” In his plan, he called for a 10-year mobilization—a time frame that mirrors the Green New Deal—including a winding down of fossil fuel production nationwide and a carbon-neutral electricity sector by 2030. Significantly, he spelled out some of the big policy changes needed to meet his goals: ending the use of coal and banning the sale of internal combustion vehicles by 2030, for instance.

Vermont Senator Bernie Sanders also embraces a tight, ambitious time line in his massive $16 trillion climate plan, which, his campaign said, factors climate change “into virtually every area of policy.” He wants to fully decarbonize transportation and electricity by 2030—a colossal undertaking, particularly since Sanders also wants to end the use of nuclear energy, which would make rapid decarbonization more difficult. Sanders says his plan would lower US emissions by more than 70 percent from 2017 levels by 2030—well beyond the IPCC goal.

There are valid questions about the feasibility of targets this ambitious, particularly given the political barriers. A major roadblock is the filibuster, which makes it largely impossible to pass significant legislation through the Senate without at least 60 votes. Sanders, who has resisted calls to abolish the filibuster, said he could enact his plan through reforms like restoring the requirement that senators stand up and speak in the Senate chamber in order to filibuster and through a legislative process called reconciliation, although it applies only to budget items. Warren, along with California Senator Kamala Harris, wants to do away with the filibuster altogether. And a number of candidates have outlined ways they could use executive action to circumvent Congress.

Despite the Democratic candidates’ unanimous pledges to the Paris framework, not everyone seems comfortable acknowledging that the brutal math of the atmosphere means stranding most of the coal and the oil and the gas that companies are betting they’ll be able to unearth for decades to come—and declining to build new infrastructure to burn it. According to a paper published this year in Nature, all of the power plants, buildings, vehicles, and other infrastructure already built will, if operated for their full expected lifetimes, send the world across the 1.5°C threshold. More than 170 new natural gas plants have been proposed or are under construction in the United States alone.

Beginning of the end: For the US to meet its Paris Agreement targets, natural gas plants like this one in North Dakota will have to be phased out.(Larry MacDougal via AP)

After several years of record-setting temperatures and political backsliding, it’s easy to forget that some things have changed for the better since the Paris Agreement took shape four years ago. For one thing, renewable energy has become far cheaper. “If you look at what countries thought they were committing to do in 2015 and the costs of their plans, we’ve now had four years of falling costs,” said Steve Herz, a senior attorney with the Sierra Club. “Everything they said they would do in 2015 is much cheaper now on the energy side than it was then. We’re sort of moving out of this narrative of ‘Who’s going to bear the costs of these emissions?’ It’s not all about costs; it’s also about opportunities. That’s most obvious in the energy sector.”

And a new youth climate movement, which has organized strikes around the world this September, is raising the political temperature. “If you combine the spotlight that the summit’s going to put on the issue and on which countries are willing to walk the talk and which countries so far aren’t—combine that with the youth mobilization, you start to build some pressure on the system to get more compliant with the Paris program,” said Alden Meyer, the director of strategy and policy for the Union of Concerned Scientists and a close observer of international climate negotiations.

“From the scientific perspective, the atmosphere is not impressed by speeches and plans. It’s only driven by emissions,” he continued. “There’s a reason why this is so hard. There are tremendous vested interests in countries around the world that benefit from the status quo, and the fossil fuel industry is very active, as it has been for decades on this issue, in trying to slow down and block meaningful action.” The industry is betting against the Paris process because it’s the easiest thing to do. That’s what the climate movement has been working so hard to change—to make not responding to the climate crisis impossible for industry and political leaders alike.