Our environment links us all: and we know that we are doing immense harm to that natural environment with our human activities. But where are the weak links? What are the potential pitfalls for the natural world, and for civilisation? In other words - if we don't change our ways - what could happen? We all know that the climate is changing and that humans are responsible for the vast bulk of the change. (If you disagree, I really hope you'll listen to this episode, and I'm happy to take on any questions you might have.) But *why* is climate change happening, what will it mean for us and what we can do to stop it? In this first episode, I will explain the physical science basis behind climate change: what is a greenhouse gas, what are feedback loops, and why does it matter that our atmosphere has gone from 280ppm of carbon dioxide to 400ppm in the industrial era?  Remember; if you enjoy the show, please tell others about it. You can visit the website at www.physicspodcast.com and you can find links there to support us via Patreon or Paypal, both of which will allow you to download bonus episodes at low, low prices.