Obama: Climate change is 'greatest threat'
3 August 2015 Last updated at 20:40 BST
US President Barack Obama has unveiled his Clean Power Plan - his strategy to cut greenhouse gas emissions from US power stations by nearly a third by 2030.
Outlining the details, Mr Obama said that "no challenge poses a greater threat to our future and future generations than a change in climate".
The president warned that this was "the first generation to feel the impact of climate change and the last generation that can do something about it."