The foreign secretary Ed Miliband will tell the Cop31 summit in Antalya, Turkey, that the climate crisis puts the national security of all countries at risk, as the two-day leaders' segment of the fortnight-long talks opens on Wednesday. Miliband arrived in Turkey on Tuesday evening for the leaders' segment on Wednesday and Thursday, which closes a summit that began on Monday.

Security as the new frontier of climate action

Miliband will frame security and defence objectives as the new 'frontier' of climate action, tying planetary heating to food shortages, economic disruption, migration and conflict. He will say climate breakdown is one of the greatest national security threats the world faces, citing food security, threats to infrastructure and population movements, and that the consequences of three decades of failed emissions cuts will drive hardship and insecurity for billions of people.

In his prepared remarks he describes 'science fiction' scenarios of widespread destruction as already coming true.

Fossil fuel shocks as the norm

The speech points to soaring oil prices this year after the Iran war, which led to rampant inflation and interest rate rises from central banks; Miliband says such fossil fuel shocks will wreak further harm. He identifies Russia and then Iran as powers that have exploited global chokepoints and systemic overreliance on fossil fuels, warning that 'next others' would follow.

The result, he argues, is that economic shocks from fossil fuels are now the norm rather than the exception.

The 1.5C overshoot and the climate fightback

Temperatures have exceeded the 1.5C threshold of global heating above preindustrial levels for two years and are unlikely to subside significantly, making an overshoot of the threshold now inevitable. Miliband will argue that this requires stronger policies to stop heating accelerating and to seek ways of returning temperatures to safer levels in coming decades.

His proposed measures include:

• •more investment in clean energy and its use in transport and heating
• •urgent action to cut methane, a powerful greenhouse gas
• •protecting and expanding forests
• •doubling down on cutting greenhouse gas emissions and building resilience to extreme weather

He is calling next year 'the year of climate fightback', with governments, movements and communities across the world stepping up to defend the shared home.

A veiled swipe at home and summit absences

In a veiled swipe at the Conservatives and Reform UK, who want to scrap emissions-cutting efforts, Miliband says those who ignore climate change put national security at risk. At home, Burnham's government faces criticism from campaigners over policies said to push the UK off-track for its net zero by 2050 target: plans to weaken the 2030 electric vehicle mandate for carmakers, approval of the Jackdaw gasfield in the North Sea, and consideration of licensing the Rosebank oilfield west of Shetland.

Australia's prime minister Anthony Albanese and Turkish president Recep Tayyip Erdoğan open the leaders' segment, with speeches from UN secretary general António Guterres, Brazilian president Luiz Inácio Lula da Silva and Ethiopian prime minister Abiy Ahmed, whose country hosts next year's Cop. China's Xi Jinping, India's Narendra Modi, France's Emmanuel Macron and Germany's Friedrich Merz are skipping Cop31, while European Commission president Ursula von der Leyen will attend.

UK prime minister Andy Burnham is expected to travel on Wednesday for bilateral meetings with fellow world leaders on Thursday.