As human beings, we are vulnerable to confusing the unprecedented with the improbable. In our everyday experience, if something has never happened before, we are generally safe in assuming it is not going to happen in the future, but the exceptions can kill you and climate change is one of those exceptions.

The moral imperative to make big changes is inescapable...that what we take for granted may not be here for our children

I am Al Gore, and I used to be the next president of the United States of America.

It took me a bit to realize how big the changes have been in the last decade. In so many places - electricity from solar and wind is cheaper than electricity from fossil fuels, and now the batteries are coming down in costs very quickly. So it's very exciting news that needed to be told.

What we've often seen is that when we Americans say, look, we've got to reduce pollution, business - some businesses complain about it, but almost every time, it's turned out to be easier and cheaper and accomplished faster, and they've gained confidence, and then we go farther.

The sooner we switch away from carbon-based fuel and start relying on renewable energy sources available in the United States, the sooner we will grow our economy by creating the millions of new jobs that will come from retrofitting homes and businesses, building smart grids, renewable energy systems and planting trees and all the rest. We need to create a lot of jobs that can't be outsourced.

Where solar energy is concerned - and wind energy and battery storage and electric vehicles and efficiency technologies - that is what we are now seeing. So, yes, I'm very optimistic, but anyone who works on the climate crisis has an internal struggle between hope and despair. I won't deny that, but hope has always prevailed in my outlook.