There is plenty more to geophysics than climate, so there were three very accessible climate change talks in huge rooms at the AGU meeting in San Francisco last week. Of the plenary climate change talks, Hansen’s got most of the press attention and perhaps Lonnie Thompson’s got the most attention from the attendees, but I thought Richard Alley’s was the most interesting and compelling.
Here’s a slide of Alley’s that I think presented nothing new to climate scientists, but that the public seems not to understand. The climate disruptions we are seeing now are very small compared to the ones we are worrying about. The importance of the past record is in confirming our understanding, but our expectation in business-as-usual scenarios is very much worse than a linear extrapolation.
Please also note that so far, we have been exceeding the steepest of the standard scenarios. Also note that as Dr Alley points out, the fact that the graphs traditionally end in 2100 doesn’t mean the temperatures don’t keep going up after that.
So what does a warming of 6 C portend? There’s a book out about that called Six Degrees that you might want to have a look at. To give you an idea of the scale, warming over land is typically double the global average, and 12 C is about 20 degrees F.