My latest DeSmogblog post is a rundown of my little debate with Michael Shermer about global warming, which can be heard at roughly minutes 5:30-13:00 on the latest podcast. I doubt I'll change Shermer's mind, but I really am not satisfied with his "wait and see" position on this issue. Here are some of the reasons I give at DeSmog:
First, the excess CO2 that we put in the atmosphere lasts there for centuries—so if the warming isn’t on the low end, we’re stuck with it. This suggests that waiting around could be a pretty bad idea. Is that a risk worth taking? Second, we know what the planet was like with vastly elevated levels of CO2 in the Earth’s past. Here’s the extreme, as described by Harvard’s Dan Schrag: “50 million years ago, we believe that carbon dioxide was between 4 and 10 times higher than present. At that time, sea level was 100 meters higher, the deep ocean was 12 degrees C (compared with 2 to 4 degrees today), crocodiles lived on Greenland, and palm trees lived in Canada.” Shermer might reply that we’ll never let it get that far, and that may be true. But crucially, the melting of the Greenland and West Antarctic ice sheets happens somewhere along the way to the crocodiles-on-Greenland world, and while we don’t know exactly where that is, there are reasons to think it is much closer to where we are now than to the world Schrag describes. Greenland alone contains enough water to raise sea levels globally by as much as 7 meters, and published evidence suggests that Greenland can be destabilized at somewhere between 400 and 560 parts per million of carbon dioxide in the atmosphere. And we’re already pushing 400. And that’s just Greenland.