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The war on Iran, which may still be a long way from over, has triggered an energy challenge that highlights the world’s collective failure to face the looming threat of climate disruption. But in a most frightening way, the use of nuclear war has also been explicit and immediate.

This moment now condenses two existential threats – climate disruption and the threat of nuclear war – into one crisis, and one that will remain long after this war subsides.

For more than a decade, I have argued that climate change is not just an environmental concern but a fundamental threat to national and global security. I have pressed governments to conduct rigorous risk assessments, to treat the destabilisation of planetary systems with the same seriousness they apply to military threats, and to act with urgency while there is still time. That argument stands.

This year has seen newly created conditions for nuclear escalation that no responsible security leader can observe in silence. How else can we understand the threat by the US president that “a whole civilisation will die tonight”?

My working life was grounded in security risk assessment. Over 42 years in the Royal Australian Navy, culminating as chief of the defence force, I learned that the first duty of strategic leadership is to call threats clearly, without flinching from inconvenient conclusions. Climate change has been my focus for the past two decades, but nuclear escalation is now also at the forefront of my concerns.

The current situation has several features that should alarm any serious strategist.

First, the United States and Israel launched a large-scale war against a sovereign nation, during active diplomatic negotiations, without consultation with their major allies. This is not a coalition: it is two countries, diplomatically isolated, pursuing a war with no clear exit and no agreed end-state. Even with the ceasefire, what “victory” looks like is unclear, and the likelihood of further escalation still exists.

Second, the threat of escalation remains, from both sides. Donald Trump has issued ultimatums, from threatening to strike Iranian power plants to destroying the country for a thousand years. Iran has threatened, in kind, to target energy and water infrastructure across the region. These are not abstract warnings, but point towards a threshold that, once crossed, cannot be reversed.

Third, the conditions for catastrophic miscalculation are always present: erratic leadership, intelligence failures, not listening to advice, extreme pressure on decision-makers, disrupted command structures, dispersed and partially unknown nuclear material, and allies without a common view about a diplomatic off-ramp. In my experience, this is precisely the sort of configuration in which wars go to places no one intended.

Fourth, crimes against humanity have become a strategic threat. What worries me most is what we have seen developing in recent years and in this war – the nuclear threat, the trashing of the Geneva conventions, war propaganda based in apocalyptic religious language – may become a new norm.

The closure of the strait of Hormuz has created an acute global energy shock. Higher oil prices will echo through the global economy for many months, if not years, accelerating inflation and economic instability across the Indo-Pacific. Countries with fragile energy transitions face pressure to extend fossil fuel use, precisely the opposite of what the climate requires. Military resources and political attention have been consumed by a conflict with no climate dividend. Proliferation pressures, if Iran exits the treaty on the non-proliferation of nuclear weapons (NPT) as it is contemplating, will reshape the strategic calculus of governments across the region and beyond.

At the same time, the diplomatic architecture needed to address climate change is being corroded by a war conducted unilaterally and without mandate. These are not separate tracks. They are the same set of conditions leading to catastrophic outcomes.

Australia is not a party to this war. That matters, but it is not sufficient. As a regional power and signatory to the NPT, Australia has responsibilities tied to the strength of the international order. I am calling on the Australian government to take four steps.

The Australian government should begin by conducting and releasing a nuclear escalation risk assessment. The Office of National Intelligence should assess escalation pathways, consequences for Australia and the region, and points of irreversibility. The public deserves to understand what is at stake.

It should also use every diplomatic channel to counsel restraint now and in the coming months. Australia’s relationships carry weight. The message should be clear: escalation towards nuclear use would be catastrophic and pursuing regime change without allied consensus or a credible end-state is not strategy: it is a gamble with civilisational stakes.

Australia must also refuse any form of complicity in nuclear use. It should state clearly it will not provide intelligence, basing, logistics or political cover for nuclear weapons under any circumstances.

Finally, Australia should champion de-escalation at the upcoming NPT review conference. Iran’s potential withdrawal would be a proliferation event of historic consequence. It should work with partners, the International Atomic Energy Agency and the UN to construct a pathway for Iran to return to the non-proliferation framework in exchange for security guarantees.

Both the climate and the nuclear threat are real. Both require full attention. And both require governments willing to act on evidence, speak plainly about risk, and lead rather than follow events. Australia can be that kind of country.

• Admiral Chris Barrie AC, RAN (retired) is the former chief of the Australian defence force (1998–2002), founder of the Australian Security Leaders Climate Group and honorary professor at the Strategic and Defence Studies Centre at the Australian National University