Climate change: how grave the threat?

There is now no dispute about climate change: it is happening, and human activity is driving it. Each day, the threat this poses becomes clearer--threatening our civilisation and also the survival of our species. The immediacy of this threat is also now recognised: it is not something 'for the next millenium' but for our lifetimes and those of our children. Without urgent action, the future is grim. But we can all respond to make the difference. And the time to do so is now.