Mark Gongloff and Liam Denning

A second Donald Trump presidency would be a nightmare for Earth’s climate (among other things). But in the same way your immune system builds up defenses after exposure to a virus, efforts to fight global warming are stronger now than the first time Trump attacked them. But he could still do significant damage from the White House.

In his first term, Trump pulled the U.S. out of the 2015 Paris climate agreement, rolled back environmental regulations, unleashed oil and gas drilling, and more. His advisers seem to think he didn’t go far enough. Report after report after report quotes them planning for “all-out war on climate science and policies” that will make first-term Trump look like Al Gore by comparison.

President Joe Biden has taken flak from environmentalists for approving the Willow project in Alaska and overseeing a surge in exports of liquefied natural gas. But he has also driven significant investments in the green-energy transition, starting with the $1 trillion bipartisan infrastructure bill and the Inflation Reduction Act’s nominal $370 billion in climate spending. He has limited oil exploration in the Alaskan wilderness and effectively frozen new LNG export terminals. All told, he has taken climate more seriously than any predecessor since Jimmy “Solar Panels on the White House” Carter.

Trump could quickly, and with gusto, wreck much of that progress. Here’s a survey of some of the strengths and weaknesses the climate movement would bring to a second Trump term.

Most vulnerable are Biden’s climate-related executive actions, including rejoining the Paris accord and ordering the federal government to decarbonize by 2050. Trump can undo these with the stroke of a pen on his first day back in the Oval Office. Biden himself canceled 11 of Trump’s climate-related orders on his first day.

It will be trickier to undo the IRA, which could funnel government support to the green-energy transition for years. The analogy here is the Affordable Care Act, passed under the administration of Biden’s former boss. Republicans campaigned relentlessly against the ACA but could never repeal it. In the IRA’s case, most benefits flow to red states and districts — election battleground Georgia figures prominently — making any such effort particularly awkward, especially if Democrats hold at least one chamber of Congress.

But Trump could hamstring the IRA by tweaking Internal Revenue Service regulations to make accessing IRA tax benefits more difficult. Senator Joe Manchin of West Virginia, whose vote for the IRA was crucial, has railed against the Biden administration ever since for interpreting its domestic content provisions in ways that prioritize green, rather than protectionist, elements. Trump, who has dragged his own party to support protectionism, would surely reverse those priorities. He could also effectively shut down the Department of Energy’s Loan Programs Office, which acts like a cleantech venture fund. 

The nascent green transition still needs government support to reach its full potential. But local policies and irresistible economics kept cleantech chugging along during Trump’s first term. Despite Trump’s promise to bring back “clean, beautiful coal,” the dirty fuel’s percentage of US energy generation tumbled from 31% to 20%, its fastest decline in any one presidential term. Coal employment tumbled 24%. Renewable energy’s share rose to 9% from 6% at the same time. Texas overtook California in renewable energy capacity. This all happened not because Trump was too liberal but because it simply became cheaper to generate power with natural gas and renewables.

The economics make even more sense now. In the years since Trump first took office, solar photovoltaic module prices have fallen by two-thirds and lithium-ion battery prices have been cut in half, notes the UK research firm Capital Economics. Total battery costs have plunged 99% over the past 30 years, while battery density has increased fivefold, according to the nonprofit green-energy advocacy group RMI. This is a solid foundation for everything from electric vehicles to grid storage.

Numbers like these, along with consumer demand for greener products, are strong incentives to keep corporate America decarbonizing. A recent PricewaterhouseCoopers survey of 4,702 global CEOs found 79% had plans to boost energy efficiency while 71% were working on “climate-friendly products, services or technologies.” Hundreds of US companies have built net-zero emissions pledges into their business plans. Even the Republican war on environmental, social and governance investing doesn’t seem to have wiped out such wokeism at companies, according to a recent KPMG survey.

Regulations are much harder to undo than executive orders, and the Biden administration is trying to finalize climate rules in time to avoid a congressional review if Republicans sweep the board. The bureaucratic molasses in which big government often wades can also help. For example, it takes four years for a country to fully leave the Paris climate agreement; Trump’s first stab at this didn’t take effect until he had already been voted out of office.

But Trump might get another four years to pack the federal courts with judges sympathetic to his wrecking-ball approach to the climate. And the Supreme Court’s right-wing majority might soon deliver another helping hand in the form of overturning the so-called Chevron doctrine, which gives agencies some latitude to interpret regulatory law. Such deference is a critical, if largely unnoticed, mechanism for applying energy and climate policy. And Trump may revive his plan — which Biden reversed — to purge the federal bureaucracy by designating some of their ranks as “Schedule F” employees, stripped of civil service or union protections, making it easier to staff up with MAGA acolytes. 

Kevin Book of ClearView Energy Partners, a Washington-based analysis firm, raises another wild card: the Senate filibuster. This check on congressional power has been eroded by both parties over the years as obstructionism has collided with legislative ambitions. With Trump an inherent lame-duck president in a second term, a GOP-controlled Senate might be tempted to overturn it to cement legislation quickly. This would, of course, carry the seeds of counterrevolution; once this check on congressional power is gone, the idea of cementing anything with legislation would lose its potency. In that case, “we may be looking at a new world,” Book said.

Fortunately, Congress and the White House don’t have a monopoly on climate influence. Dozens of US cities and 23 states, along with Puerto Rico and the District of Columbia, have some sort of net-zero emissions target. These include red states such as Louisiana and Nebraska and swing states such as Michigan and Wisconsin. Watching Trump trying to sabotage climate progress might inspire local governments to fight back even more aggressively.

Other countries are poised to leave a Trump-led US in the dust. The planet’s biggest carbon polluter, China, is already on track to add more renewable capacity in the next five years than every other country combined, according to the International Energy Agency. The European Union has cut carbon emissions by 30% since 1990 and plans to spend 30% of its annual budget on climate projects until 2027. In the fourth quarter of 2023, wind provided more EU electricity than coal for the first time, according to the research firm Ember. For all the talk of a struggling market for electric vehicles, global EV sales jumped 69% in January from a year earlier, according to battery consultancy Rho Motion. 

Trump’s attitude about climate, as with so many other subjects, is stuck in the past. If they turn the political clock back to 2016, American voters will make it more difficult to limit global heating to merely disastrous levels. But the damage can be contained, if the rest of us are willing to work that much harder to secure the future.

Mark Gongloff is a Bloomberg Opinion editor and columnist covering climate change. He previously worked for Fortune.com, the Huffington Post and The Wall Street Journal. Liam Denning is a Bloomberg Opinion columnist covering energy. A former banker, he edited The Wall Street Journal’s Heard on the Street column and wrote the Financial Times’ Lex column.