Olaf has asked me to post about the Stern Report, which in case you missed it expects climate change to incur $7 trillion (that's with a T!) in losses for the global economy, but could be averted for 5% of that.
Unfortunately, the Stern Report is 700 frickin pages long, so this isn't something we I can give a 300-word summary of. Rather, I'll be trying to go through the report over the next little while, and extracting the neat bits.
The short version is that Stern took the science of climate change seriously, and is presenting what I think is a reasonable estimate of the worst-case scenario. The skeptics see this and say "Oh, it won't be that bad." Well, sorry, no. Stern's estimates are worse than the IPCC's for the simple reason that in the intervening time, the science has gotten much more alarming - specifically, the discovery of a number of positive-feedback loops.
In five more years, I would be upset, but not surprised, to see Stern's own estimates eclipsed by even more alarming science. This isn't a sign of runaway sicentist hysteria, but a sign of runaway climate change.
There's one bit so far that I don't think has gotten enough attention - Stern's admonition that prices alone will not save us. That is, increasing the price of gasoline, coal, or whatever will not actually reduce the risk of climate change, and in fact may increase our risks. The simple fact is that as oil prices have increased, the resource pool has grown to include not just the tar sands, but also potentially coal-to-liquids and oil shale.
Stern estimates that even at current prices, there's enough economically-available carbon in the ground to almost triple the preindustrial levels of CO2 - an eventuality I don't even want to think of. The idea of sunny beaches in the NWT scares the crap out of me.
Bizarrely, I find myself in agreement with our PM and Environment Minister on this point: if we're serious about pollution, regulation and law are more efficient means of prohibiting certain behaviours than taxes. The main difference, of course, is that I actually am serious, whereas Harper and Ambrose are not.