But it's also been a window into the hasty, sloppy, and legally dubious ways that they've gone about it. "One of the hallmarks of this administration is how incompetently they're doing this," says Doniger. "It shows up in how slowly they've been able to work, and how flimsy their legal rationales are." Almost all of Trump's attempts at deregulation — some 100 rules that he's tried to eliminate or weaken — are being challenged in court, and environmentalists are steadily winning. According to the Institute for Policy Integrity at New York University, the Trump administration has lost 69 of the 83 legal challenges it's faced in its deregulatory blitz.

"We were saved by their incompetence," says Andrew Wetzler, from the NRDC Action Fund, mainly by their failure to follow basic rule-making procedures. They rushed through the process, often shortening or entirely skipping over the required 60 days for public comment, which provided a clear opening for their rule changes to be challenged in court. The administration's ineptitude has given environmentalists hope that if Trump loses the election, the policy impact of his unrelenting pro-fossil fuel agenda could ultimately be short-lived. "If he's a one-term wonder," says Doniger, "the biggest consequence of the Trump administration may just turn out to be lost time."

But time, at this hour of the climate fight, might be our most precious resource. As we stumble ever closer to the collapse of ice sheets, oceans and forests, the range of meaningful action we could take narrows. There is now believed to be more carbon dioxide in the air than any time in the last 3 million years. Our oceans are on track by the end of this century to become more acidic than they've been in some 15 million years — when they were enduring a major extinction event. Those oceans are also rising steadily enough to threaten the homes of 150 million people in the next three decades. "We lost years at a critical time," says Wetzler. "We're on the precipice of a number of climate and biological tipping points." And, he says, we won't fully understand the impact of that loss for years.

If Biden wins in November, environmentalists say, his administration would have a slim window of opportunity to get our agencies back on track to meet the enormity of the climate crisis. "It means being aggressive from day one," says Brett Hartl from the Center for Biological Diversity Action Fund. "And not futzing around — knowing what you're going to do and implementing it immediately."

Making up for the lost time won't be easy. Despite his slap-dash approach, Trump still managed to scramble the trajectory of American climate policy, creating a tangle of legal fights that will have to be cleared up for U.S. climate policy to move forward. And he left almost no part of our environmental regulatory structure untouched — greenlighting fossil fuel infrastructure like the Dakota Access and Keystone XL Pipelines, setting us back on emission-reduction goals by reversing the Clean Power Plan and higher fuel-efficiency standards, and gutting the federal agencies that should be at the helm of our climate response.

So how difficult will it be to unscramble this mess? It would have to happen in three parts, environmentalists say, and all three would have to start on day one. First, Biden would have a powerful arsenal of executive tools available to him — if he chooses to use them. A coalition of over 500 environmental groups has already assembled a plan for how he could effectively jumpstart our fight against the climate crisis using executive powers, which would avoid both going through Congress and the lengthy federal rule-making process.

Using executive power, Biden could declare a national climate emergency. It wouldn't just send an important message to Americans — and the rest of the world — that we're taking the climate crisis seriously; it would give the administration the power to mobilize the government on a massive scale, like ordering the Secretary of Defense to redirect military spending toward the rapid development of clean energy.

Biden could also immediately order federal agencies to reverse the climate rollbacks Trump introduced through executive order — like allowing oil and gas companies to side-step state approval — and start issuing his own. Most urgently, Biden would have the power to keep more fossil fuels in the ground: He could direct the Secretary of the Interior to halt oil-and-gas leasing and fracking on federal lands, reinstitute the ban on exporting crude oil, and order all federal agencies to deny permits for new fossil fuel infrastructure, like pipelines, storage facilities, and refineries.

He'd also be able to change the ways that money moves through the energy sector. He could prohibit the U.S. government from financing fossil fuel programs overseas and end all Department of Energy loans for fossil fuels stateside, while also requiring the Federal Reserve to manage climate risks — forcing it to acknowledge the current and future impact of climate change on our economy.

Many of these tools were already available in the Obama era, but the administration chose not to use them. For example, "the Clean Air Act is actually quite clear that you have the authority to set national ambient air quality standards," says Hartl. "It would have been incredibly bold, and it actually wouldn't have had the problems that the Clean Power Plan had. They could have really moved the needle on greenhouse gases in a very, very powerful way." But, Hartl says, the Obama administration shied away from these kinds of actions for fear of political consequences.

Biden would face a very different national landscape. At the beginning of this year, two thirds of American adults said that protecting the environment should be a top priority of the federal government, up from only 30 percent at the beginning of Obama's first term. In a poll last week, likely Democratic voters ranked climate change as the most important issue to them in this election, and Data for Progress, a progressive think tank, has found that talking about climate change could actually help persuade voters who are on the fence to vote for a Democrat. All of this is to say, a Biden administration could have an unprecedented political mandate to take action on the climate crisis.

In addition to issuing executive orders, beginning on day one Biden would also need to start the process of unwinding the deregulation efforts that Trump carried out through the federal rule-making process — like rollbacks on the Endangered Species Act and fuel-emissions standards — and writing new ones to take their place. Environmentalists are confident that a new administration could systematically undo each rollback, but that process could take two years, according to Hartl.

And the Biden administration would need to learn from Trump's mistakes. Legal challenges from the industries that these regulations impact — the American Petroleum Institute, the National Mining Association — are inevitable, "so you have to go in and be prepared to defend it the first time," says Hartl. That means following the process to the letter: establishing rules with legal backing from legislation like the Clean Air and Clean Water acts; opening the rule up to public comment; and then presenting a final rule that can stand up in court. Unlike Trump's deregulation efforts, which were fighting against decades of environmental legislation, the law would be on Biden's side. "The reality is that when Congress passed these laws," says Hartl, "they were designed to make the environment better."

Finally, Biden would have to start hiring like mad. Over the past four years, Trump's EPA and Interior Department have hemorrhaged talent. The Bureau of Land Management moved the majority of its staff out of Washington, D.C., leading some 70 percent of that staff to resign, and the EPA is nearly as small as it was during the Nixon era, when the EPA was founded. "That pattern, in the most extreme way, is mirrored throughout the environmental agencies," says Wetzler. "There's been a real brain drain of people who can't stand in an agency and support the agenda under the Trump administration, and we'll have to put back the pieces of very demoralized, and in some cases broken agencies."

But from those ashes, Biden could build a coalition of climate advocates across his Cabinet. His transition team, and the 4,000 people they appoint, are arguably more influential than any campaign promises he could make. "Personnel is policy," says Jamal Raad, co-founder and campaign director for Evergreen Action, founded by former staffers of Gov. Jay Inslee's presidential campaign. "We need to choose regulators that have a climate lens," and that lens doesn't end at the EPA — it can reach the Department of Agriculture, where we have to reimagine our food production to work with our changing climate, or the Treasury, where regulators could interpret the Dodd-Frank consumer protection act to include climate risks. And within the White House, Raad says, Biden could create a National Climate Council that's equivalent to the National Economic Council. "There needs to be a plan to reorient the federal government so that climate is a lens in all decision making."

Heading into the general election, pressure from the left wing of the party shaped Biden's $2 trillion climate plan, which is "a green new deal in all but name," wrote activist and journalist Julian Brave NoiseCat. "It's the most progressive, forward-leaning environmental plan that any candidate for president has ever released," says Wetzler of the NRDC Action Fund. "It would represent incredible progress." And while the Biden campaign hasn't laid out a timetable for the plan, "the Biden team has been signaling their prioritization of climate by making it central to their economic recovery plans," says Raad. "I think that folks should be cautiously optimistic — but vigilant — on the prospect of climate being a priority early in the first term."

Of course, this all hinges on what happens in November. And if Trump is re-elected, his administration would have the chance to establish a legacy of more than just incompetence and squandered time. Four more years of Donald Trump being in charge of the environment could permanently alter the American landscape.

In some cases, it would give the Trump administration time to fight back against the legal challenges they face, leaning on courts that they've stacked with anti-environmental judges. And damage could be done that will be near impossible to undo — rules can be changed, but mines can't be unmined. The Trump administration has pursued the largest rollback of federally protected land in U.S. history. Bears Ears National Monument in Utah, for example, which Trump shrunk by 85 percent in 2017, is in the crosshairs of uranium developers. Trump's move has been mired in lawsuits, but a second term could give them the time to untangle them, and hand the land over to the uranium lobbyists.

Likewise, drilling in the Arctic National Wildlife Refuge was just approved in August, leaving little time for leasing, let alone actual development, before Inauguration Day. But if Trump wins, those leases are likely to move forward, as will the roads, pipelines, and oil rigs that come with them, doing permanent damage to a vital and fragile ecosystem. "Over time you're looking at millions and millions of acres of fossil fuel leasing," says Hartl from the Center for Biological Diversity Action Fund. "And eventually, once you get to the point where they're actually putting drills in the ground, it's very hard to undo that. You're locking in a tremendous amount of fossil fuel infrastructure."

Trump's influence on the Supreme Court looms heavily for the environment as well. With Trump already raring to appoint a new justice to replace Ruth Bader Ginsburg, a second term is likely to offer him a fourth Supreme Court appointment, which would mean the highest court would house seven Republican-appointed justices. When you're suing over environmental issues, the court's make-up can be the difference between having your day in court, and not. "For example, there's a general judicial doctrine called 'standing,' or your ability to go to court to pursue your aggrieved interests," explains Hartl. "Conservative judges want to narrow who has standing as much as possible, because that limits access to the courts. When you're fighting for the environment, and your interest is protecting an endangered species or the atmosphere or the water, they've already made it hard for us to go to court, to have standing. And they can narrow it even further so that we don't even have recourse. Our ability to just fight for the environment is at stake."

The climate movement has never been more clear on what it is fighting for and what it needs to do, and finally has a presidential candidate who is signaling some willingness to do it. The prescription is fairly simple: Stop burning fossil fuels so we can begin drawing down the carbon in the atmosphere that's overheating our planet and disrupting the systems that have supported life on Earth as we know it. The president has a lot of power to take that action, and we have no time to lose. "It's true that we have 30 years [before an irreversible climate collapse], but when you act on that 30-year scale really affects how radically you have to act," says Wetzler. "If you think about where the United States was at the beginning of the Trump administration — and where the world was, in terms of taking climate change seriously — it's a huge, squandered opportunity." This November, we can choose to act, and set ourselves back on course. "If this is a one-time, Black Swan event, we're probably going to recover as a nation," says Doniger. "This is the project of the century."