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.
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.
There are folks who will equivocate. They'll say, 'You know, I'm not a scientist.' Well, I'm not either. But the best scientists in the world know that climate change is happening.
And yes, my plan will continue to reduce the carbon pollution that is heating our planet - because climate change is not a hoax. More droughts and floods and wildfires are not a joke. They're a threat to our children's future. And in this election, you can do something about it.
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 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.
We do not know how much our climate could or will change in the future. We do not know how fast change will occur or even how some of our actions could impact it.