At the annual United Nations climate summit in Bonn in November 2017, parties to the 2015 Paris Agreement made incremental progress on the operational details needed to implement the landmark accord. If the agreement is to have any chance of keeping global warming below 2°C, its details must be finalised by this year’s summit, in December 2018. In December 2017, the UN Security Council held an Arria-formula debate on ‘preparing for the security implications of rising temperatures’. At both gatherings, the United States was conspicuous by its absence. The new US National Security and National Defense Strategies no longer explicitly recognise climate change as a security threat, even though the US military itself does so in practice. US President Donald Trump’s reversal of long-standing US climate policy appears to be informed less by a consistent strategic vision than by domestic politics, ideology and short-termism, yielding an inconsistent approach that is ultimately damaging to US interests.