Climate change will lead to growing international tensions, the US intelligence community has warned in a bleak assessment.
The first ever National Intelligence Estimate on Climate Change looks at the impact of climate on national security through to 2040.
Countries will argue over how to respond and the effects will be felt most in poorer countries, which are least able to adapt.
The report also warns of the risks if futuristic geo-engineering technologies are deployed by some countries acting alone.
The 27-page assessment is the collective view of all 18 US intelligence agencies. It is their first such look-ahead on what climate means for national security.