There’s a new, stark reality we must face: Donald Trump’s victory will push the Earth system further down a perilous path towards three degrees Celsius of global warming or more, with catastrophic consequences for human civilisation and the environment.

This moment requires clarity about the existential nature of the climate threat to humanity’s future; and a collective commitment to decisive action, because time has run out for slow, incremental policy change.

With global leaders gathering at the 29th annual UN climate policy-making meeting in the petrostate of Azerbaijan, the born-again climate denialist President Trump will cast a long shadow over proceedings. His denialism will trigger others to do less.

Trump will soon preside over the world’s leading fossil-fuel producing nation, and his stance on climate — to supercharge fossil fuel development, slash pollution regulations and pull out of the Paris Agreement — is the antithesis of what’s required. It will push up US emissions by four billion tons by 2030. His agenda absolves governments of climate responsibility, and is a direct assault on global efforts to prevent and mitigate the crisis.

An informal alliance of climate-denying, politically authoritarian petrostates including the United States now looms. But effective climate action requires unprecedented global cooperation, rather than conflict, and courageous political leadership: a collective architecture for survival and the political architects who make it their primary purpose in public life.

Climate is the biggest threat to Australians’ future, and security dependence on an alliance with a country whose government will be climate denialist, authoritarian and increasingly antidemocratic is a nostalgic illusion.

What are the common values shared in a US-Australia alliance in the Trump era? The liberal-democratic tradition? Adherence to the UN’s national self-determination and human rights framework? The rights of women? Respect for diversity? The Geneva Conventions and the rule of law? Care for nature? None of these exist in Trump World. We share nothing with him.

Australia’s global security strategy should be driven by the need to protect all people from climate breakdown, and a commitment to deep cooperation with nations who prioritise climate disruption risks with climate-focused agreements on tax, trade, technology, finance and equity.

The nature of climate risks — global, cascading and so large as to be unquantifiable in monetary terms — means that their primary management is beyond the capacity of markets, as are other existential risks such as war, pandemics and large-scale natural emergencies. This reinforces the leading role of governments in assessing the risks, planning and coordinating the economic transformation and building global climate–security cooperation to do so.

Australia has arrived at a strategic crossroad that is not just a matter of environmental policy but a national, regional and global security issue of unprecedented scope. Australia must question how to manage its relationship with the US and not be dragged down by a Trump-led climate regression. At the same time, Australia must scale up major collaborations with Europe, China, and other proactive nations striving to curb emissions and avert disaster, even as the US continues to waiver.

To not send a clear signal to the world is more than just environmental folly; it would be an act of self-sabotage. If Australia fails to align with forward-looking nations it risks its long-term security and economic stability. Tying our fate to a country that will ignore the existential climate reality is a gamble on our own survival.

It’s a moment for Australia to lead by choosing responsible, reality-based diplomacy that acknowledges the climate emergency, and positions the nation as part of the solution, not the problem.

There’s a grave danger that another Trump term will lower the bar for global climate action and create a new, devastating benchmark: the “at least it’s better than Trump” low bar. The consequences of such complacency will be measured in degrees—and in lives. We can no longer let a lowest-common-denominator approach to climate action become the norm, for that will cement a future that no one will be able to inhabit.

The world stands on the precipice. Australia must look beyond old alliances and embrace a new paradigm of global cooperation to counter climate disruption.