The biggest threat, when it comes to climate change and pollution, isn't going to come from us because we only have 300 million people. It's going to come from China with over 1 billion people and India with over 1 billion people.
Those who deny human-caused climate change offer no compelling evidence to better explain the undeniable rise in atmospheric concentrations of greenhouse gases and global temperature.
We need to start by having a conversation about climate change. It would be irresponsible to avoid the issue just because it's uncomfortable to talk about.
The world must come together to confront climate change. There is little scientific dispute that if we do nothing, we will face more drought, famine and mass displacement that will fuel more conflict for decades.
We are willing to uphold principles that have resulted in unprecedented prosperity and security throughout Europe and around the world. With the threat of climate change only becoming more urgent, Angela [Merkel] and I focused on the need for American and E.U. leadership to advance global cooperation.
There's one issue that will define the contours of this century more dramatically than any other, and that is the urgent and growing threat of a changing climate.