Donald Trump’s triumph over Kamala Harris in the US presidential election matters for many reasons, but especially climate change.

No presidential candidate in US history has presented such a threat to global efforts to cut carbon pollution as Trump does.

After all, Trump regularly refers to climate change as a “hoax” and a “scam”, even as his home state of Florida is battered by more frequent and severe hurricanes.

So what will a Trump presidency mean for climate policy, including in Australia? Buckle up, it’s not pretty.

Pulling out of Paris and the UN climate treaty

Let’s start with international relations.

Trump is likely to pull the United States out of the Paris Agreement, the landmark international climate pact negotiated in 2015 during the Obama administration. Trump withdrew the US from the deal when he was last in the White House.

More concerningly, Trump may go further this time and attempt to withdraw the US from the international treaty that underpins the deal — the United Nations Framework Convention on Climate Change. This would cast the US further outside the global push to reduce dangerous greenhouse gas emissions, and make it harder for a subsequent president to rejoin the effort. Joining a treaty requires a two-thirds Senate majority, and legal experts are divided on whether Trump could exit a treaty without the same mandate.

Australia is bidding to host the UN climate negotiations in 2026, the so-called COP31. If it succeeds, it will have to steer the challenging negotiations without the diplomatic heft of our closest ally.

And with the US no longer working towards climate action, Australia will need to establish new alliances with governments in Europe and Asia and strengthen existing ones. For example, the new Labour government in the United Kingdom has already proposed a Global Clean Power Alliance, which Australia is no doubt considering.

Bumping up greenhouse gas emissions

The US is the second-largest emitter of greenhouse gases in the world, after China. If it doesn’t cut pollution, humanity’s climate goals will be further out of reach — and with it the chances of preserving a habitable planet this century and beyond.

In 2100, when children alive today are the same age as Trump is now, the loss of the Great Barrier Reef will be the least of their worries. They will be contending with more frequent and intense heatwaves, longer bushfire seasons, flooding and sea-level rise.

Trump has promised a complete repeal of President Joe Biden’s flagship climate legislation, the Inflation Reduction Act. That law passed in 2022 and has been a boon for clean energy. It has already provided billions of dollars in tax credits for solar panels, wind turbines and batteries, among other technologies.

But it remains to be seen whether Trump will follow through on the threat. Some Republicans support the Inflation Reduction Act, especially those whose states have benefited from the jobs and investment. In fact, more than three-quarters of clean energy investments announced by the Biden administration are in Republican districts, such as new solar manufacturing in South Carolina.

It is no surprise, then, that Republican lawmakers have already written to the leadership opposing the repeal of the climate bill. But given that Republicans have just flipped the Senate, and at the time of writing the House remains up for grabs, the repeal remains a live possibility.

Winding back environmental protection

Under Trump, the US Environmental Protection Agency will be gutted, along with many other government agencies.

Trump has committed to removing all manner of environmental regulations in his first days in office. This includes reopening oil drilling in Alaska’s Arctic National Wildlife Refuge.

That could be just the beginning. During the campaign Trump reportedly offered oil and gas executives the chance to rewrite climate and energy policy in return for US$1 billion (A$1.5 billion) in political donations — in one of the most brazen attempts to sell policy to the highest bidder.

Australia must remain on track

There will be a temptation for some political leaders here to advocate that Australia walk away from action on climate change, by pointing to Trump’s policies and claiming Australia should follow suit.

That would be a mistake. Not just because it will make another horror bushfire season more likely, or commit towns such as Lismore in New South Wales to further floods. But because it would forego the significant economic opportunities Australia can capture from a clean energy future.

The Australian government should double down on the Future Made in Australia agenda, which seeks to do just that, for example by extending production tax credits to additional clean energy industries, and boosting public finance for new renewable projects, much as the Inflation Reduction Act in the US does.

Of course, Australia should also tackle the billions doled out in subsidies to coal and gas each year, which the US failed to do under both the Biden and Trump presidencies.

Australian government officials should also work to strengthen relationships with US states working towards climate action — both with progressive states such as California, but also with Republican states that benefit from clean energy investments.

The US election result does not change the basic facts: Australia remains a lucky country when it comes to clean energy. We have abundant solar, wind and hydro power, not to mention a skilled workforce and deep expertise in large energy projects.

What’s needed now are durable climate policies that support long-term investment and build the industries of the future, such as green iron for steel production.

Australia may have lost a major ally in the climate fight. But that should only make us more determined to work with others around the world. Our largest trading partners are in Asia, and future demand for our clean energy exports will come from our region as well.

With smart policies at home and strategic engagement abroad, Australia will remain well placed to advance a clean energy transition.

This piece was first published in The Conversation.