Climate change and the biosphere: As Earth's climate warms, the effects are showing up in the planet's biological systems, from the lowliest soil microbes to the grandest coral reefs. The sixth extinction event is under way. Can humanity muster the leadership and international collaboration necessary to stop eating itself from the inside? A review of The Hot Topic: How to Tackle Global Warming and Still Keep the Lights On by Gabrielle Walker and David King. More on Break Through by Michael Shellenberger and Ted Nordhaus. Denis Dutton of Arts & Letters Daily now also sponsors Climate Debate Daily, "intended to deepen our understanding of disputes over climate change and the human contribution to it". Here are five sites to help you sway climate change deniers still out there.