During the months that Joe Biden and President Donald Trump were campaigning against each other, vast sections of the American West caught on fire. More than 5 million acres burned, and the air in California, Oregon and Washington was sometimes more harmful to breathe than in the pollution-clogged cities of India.

In the Atlantic Ocean this year, there have been more big storms recorded than in any previous year — 29 thus far, so many that the group that names storms exhausted the English alphabet and had to switch to Greek. Nine of those storms became much more intense in the span of a single day, an event that was rare before the planet was as warm as it now is.

Worldwide, the month of September was the hottest ever measured, and 2020 may end up being the hottest year. The Arctic is warming even faster than the rest of the planet, and glaciers are losing more ice each year than can be found in all of the European Alps. Sea levels now seem to be rising at an accelerating pace. In Siberia, melting ice appears to be releasing gases that cause gigantic explosions, leaving craters that are up to 100 feet deep.

Climate change is a fantastically complex phenomenon. It does not proceed at a steady pace, and scientists are often unsure precisely what its effects are and which weather patterns are random. But the sum total of the evidence is clear — and terrifying. The Earth is continuing to warm, breaking records as it does, and the destructive effects of climate change are picking up speed. Future damage will almost certainly be worse, maybe much worse.

Yet there is also a major way in which 2020 has the potential to be a turning point in the other direction. A president who has called climate change a hoax — whose administration has tried to discredit government scientists and has overhauled federal policy to allow more pollution — has lost reelection. He has lost to a candidate who made climate policy a bigger part of his campaign than any previous winning president.

The last two Democratic presidents, Barack Obama and Bill Clinton, put a higher priority on expanding health insurance than fighting climate change. Biden, by contrast, has said he will accomplish his unavoidable short-term priorities — controlling the coronavirus and restarting the economy — in significant part by fighting climate change.

He has proposed spending $2 trillion on clean energy over the next four years to put people back to work, a sum that’s almost 20 times larger than the clean energy spending in Obama’s 2009 economic recovery package. Embedding clean energy measures into other policy areas is likely to be a theme of the Biden presidency. His advisers have told me that during almost every policy discussion, they ask themselves how to incorporate climate.

The issue is simply more salient today than it was in 2008, as Gina McCarthy, who ran the Environmental Protection Agency under Obama and has advised Biden, points out. “The difference between then and now is that the issue of climate change is so much more relevant and personal now,” said McCarthy, who runs the Natural Resources Defense Council. “There is a real opportunity here that I think Biden is capturing.”

What he can accomplish, of course, will depend on Congress — and specifically on whether Democrats manage to win both Senate runoffs in Georgia in January. That won’t be easy. If Democrats don’t win both, Republicans will keep Senate control, and one of the world’s few major political parties that rejects climate science will be able to block large parts of Biden’s agenda.

But even in that scenario, he is likely to shift federal policy in a profound way. His advisers have spent months thinking about how to reduce carbon emissions through regulation rather than legislation. And Biden may also be able to win over a few Republican senators — which is all he would need — for an economic recovery bill that included billions of dollars of clean energy spending.

The fact that Biden seems inclined to make the climate a top priority does not stem from a longtime personal obsession. He is not Al Gore. But he has spent his career trying to understand where the center of the Democratic Party is moving and then moving with it. And both the Democratic Party and the country have moved on climate.

For many young progressives and political activists, who will have to live most of their lives on a planet suffering from climate-related damage, climate is the defining issue. “There’s so much pressure from the outside, from young activists — it’s very impactful,” said Rep. Kathy Castor, a Democrat from the Tampa, Florida, area who heads the House Select Committee on the Climate Crisis. Consider that Sen. Bernie Sanders made “Medicare for All” his signature issue; Rep. Alexandria Ocasio-Cortez has made the Green New Deal hers.

If anything, the attention on racial injustice since George Floyd’s killing in May has put more momentum behind climate policy. When Ocasio-Cortez and Sen. Ed Markey of Massachusetts released the Green New Deal — a statement of principles, rather than a detailed piece of legislation — last year, some moderate Democrats and climate experts criticized its breadth. It called not only for stopping global warming but also for addressing economic inequality and racism.

Now, though, that broad approach means that climate policy feels like a crucial part of another progressive priority: combating racial inequities, by reducing the disproportionate health damage that pollution causes in Black and Latino neighborhoods. Rhiana Gunn-Wright, who helped write the Green New Deal and now runs the climate program at the Roosevelt Institute, said that she used to spend a lot of time answering questions about how climate change and racial justice were connected. “I don’t get asked those questions anymore,” she added.

In addition to the activist energy, broader public opinion seems to be shifting, as climate change has gone from being a hypothetical future problem in many people’s minds to an everyday problem. In a Pew Research Center poll this year, 52% of Americans said that dealing with global climate change should be a top priority for the president and Congress. In 2009, only 30% did. In a New York Times/Siena College poll during the campaign, 66% of likely voters said they favored Biden’s $2 trillion climate plan, with only 26% opposed.

As Gunn-Wright said, “It’s getting harder and harder to act like climate change is a long-term issue that’s coming down the pike.”

Regardless of what happens in the Georgia elections, Biden’s approach to climate change will differ from Obama’s. Like most of the Biden agenda, this change reflects a larger shift in the party. In the case of climate, Democrats have become more hardheaded about the tricky politics of the issue. The change has been subtle, and no politician has ever announced it. But it has also been fundamental.

Democrats used to focus their efforts to pass a climate bill on the idea of raising the cost of carbon emissions, through either a tax or a system of permits, known as cap-and-trade. For all of the complicated details, the basic idea was simple: If dirty energy became more expensive, people would use less of it.

Many economists favor this approach because it harnesses the power of market incentives to shift millions of people’s behavior. Obama also hoped that the market-oriented approach might win enough Republican votes to get it through the Senate. It did not.

Without bipartisan support, a price on carbon has a huge political weakness. Because higher costs are the central part of the plan, opponents are able to brand it as a tax increase for hardworking families. That criticism helped defeat the Obama plan in the Senate and has also led to the downfall (or weakening) of climate policies in other countries. If a carbon price can’t pass, its technocratic elegance and economic efficiency are irrelevant.

Having learned this lesson, many progressives changed their strategy. They have moved away from a carbon price and now focus on the two other major ways that a government can address climate change. The first is to subsidize clean energy so it becomes cheaper and, in turn, more widely used. The second is put in place rules — often called standards — that simply mandate less pollution, leaving utilities and other companies to work out the details of how they will emit less carbon.

These two approaches are the core of the Biden agenda. And the creation of standards will be the most important one if Democrats fail to win both Senate races in Georgia.

Crucially, a president already has the legal authority to enact standards in the sectors that emit the most carbon, like utilities and transportation. Biden will not need new legislation to do so. In 2007, the Supreme Court ruled that the Clean Air Act applied to carbon emissions, allowing the Environmental Protection Agency to restrict them. Obama used this power, and Biden will probably be even more aggressive.

Standards can have a big effect. The Obama policies, combined with technological advances in solar and wind power, have helped reduce coal’s share of the power sector to 20%, from almost 50% in 2010. Thirty states have created their own energy standards, including California, New York, Arizona and Colorado, which has also helped. In some cases, the state-based policies are the result of a referendum.

That’s a sign that these standards tend to be more popular than energy taxes: Most Americans support pollution reductions. Opponents still portray them as tax increases, as they no doubt will during the Biden administration. “The oil industry is always going to be arguing that no matter what you do, it’s a price on carbon,” as Markey told me. But it’s easier for climate advocates to win that argument.

In some cases, Biden may use the threat of regulation to negotiate with industry. Automakers seem open to making a deal. When Trump tried to free them from Obama-era restrictions, some balked. Many auto executives understand that clean energy cars are the future. They would rather get working on the transition than have to maintain two different product lines — gas-guzzling vehicles in some places (like red states) and more fuel-efficient cars elsewhere (like California and Europe).

With a Republican Senate, the Biden climate agenda will consist of dozens of smaller pieces, rather than one sweeping piece of legislation. The Agriculture Department will create incentives for farms to emit less carbon, and the Energy Department will do the same for buildings. On Capitol Hill, the administration will try to add some clean energy subsidies to legislation on virus relief and infrastructure.

Foreign policy will also be geared toward persuading other countries to emit less. China, in particular, has shown more willingness to listen to American requests on climate change than on other big subjects, like human rights and intellectual property.

Will this be enough to avoid the worst consequences? It is impossible to know. Our chances would certainly be better if Congress were able to pass major legislation.

“We have to use every tool in the toolbox on climate action, before it is too late,” Castor said. McCarthy added: “We are way past the time when we should be looking incrementally instead of very aggressively.”

That aggressive approach depends on Democrats winning both Georgia races, which would give them 50 Senate seats and allow Vice President Kamala Harris to break ties. In that case, Democrats could pass much of Biden’s proposed clean energy spending. This money would increase spending on research and development, as well as give consumers and businesses incentives to make immediate changes. Many more families would probably buy an electric car, for example, if the government subsidized the purchase and also paid to build many more charging stations.

A Democratic Senate could also try to protect Biden’s regulatory authority from court challenges, especially given the newly conservative makeup of the Supreme Court. Some climate advocates even hope the Senate would be willing to revisit targeted carbon taxes, perhaps only for the power sector.

The biggest reason to believe that Biden’s presidency may mark a new era in climate policy is also the biggest reason for pessimism about the future. The effects of climate change seem to be accelerating. The coming years will bring more fires, more unbreathable air, more extreme storms and more flooding, as well as damage that we cannot yet predict. At some point, voters may demand aggressive action and punish politicians who put a higher priority on the profits of the energy industry than on the condition of the planet.

We’re not there yet. But Biden seems to grasp that his success in fighting climate change will go a long way toward defining his success as president.

David Leonhardt

David Leonhardt is an Op-Ed columnist for The New York Times.