From Capitol Hill to Copenhagen: Al Gore's journey to centre stage as climate change crusader.
As one of the world's best known environmental crusaders, former US Vice-President Al Gore is surprisingly optimistic about the climate crisis.
He's convinced we can save the planet and avoid "unimaginable catastrophe" simply by "making dramatic changes quickly" at every level of our lives.
And Al Gore is no stranger to making positive changes when things don't go to plan.
In his life he's dealt with personal tragedy - when his son was badly injured in a car accident, and political tragedy - when he lost the 2000 presidential election to George W Bush, despite winning the popular vote.
On each occasion he re-evaluated and took a radical change of direction in life.
After the 2000 election, he reinvented himself as a climate campaigner, taking his message to the world stage with a new persona and a passionate plea for change.
He won the attention of millions around the world with his global concert Live Earth and film An Inconvenient Truth - ultimately winning two Oscars and the Nobel Peace Prize for his work with the Inter-Governmental Panel on Climate Change.
And now he's published a new book laying down the specific changes we need to make to solve the climate problem - changes to industry and to our lives to reduce our carbon imprint.
Matthew Bannister spoke to Al Gore about why he remains so optimistic about the planet, the changes he prescribes, and the personal hurdles in his own life that taught him how to make change.
Our Choice by Al Gore: A Plan To Solve The Climate Crisis is published by Bloomsbury.