Originally Posted by cdcox
It's not just CO2, its methane, CFCs, volcanoes, and everything else that goes into the forcings. More information which clearly shows that the forcing follows scenario B most closely:
Doing a little research on my own, scenario A assumed exponential increases in global warming gases, while scenario B was a linear increase. If you look at emissions data both CO2 and methane increases have been linear, while CFC emissions have decreased. So where you get the idea that our emissions have been above scenario A I have no idea.
I love that you use as "proof" someone who "adjusts" Hanson's model AFTER THE FACT. It amazes me that you (and others) have no problem with this. Hey if Hanson had only used the CURRENT accepted climate sensitivity parameter.. he would have been much closer (close enough that we'll "fudge" and say it was accurate!).
I get my data from... hold on this is the weird part... OBSERVED DATA. Not from projections or other models.
Here is what Hanson said ...
“Specifically, in scenario A CO2 increases as observed by Keeling for the interval 1958-1981 [keeling et al, 1982] and subsequently with a 1.5%/yr growth of the annual increment.”
“In scenario B the growth of the annual increment of CO2 is is reduced from 1.5%/yr today to 1%/yr in 1990, 0.5%/yr in 2000 and 0 in 2010; thus after 2010 is constant, 1.9 ppmv/yr.”
“In scenario C the CO2 growth is the same as scenarios A and B through 1985; between 1985 and 2000 the annual increment is fixed at 1.5 ppmv/yr; after 2000, CO2 ceases to increase, its abundance remaining fixed at 368 ppmv.”
I haven't actually run the hard numbers for a few years but last I checked it was almost exactly scenario A, feel free to check it for yourself. But a quick eyeballing of this graph...
Shows a slight exponential increase.. you know.. something around 1.5-2%... it most certainly isn't the straight line that Scenario B calls for.
Yes you can bring up the CFC or methane or whatever arguments and there we start to deviate from his established scenarios but I can further show that he was still off by a significant margin.
THE ONLY WAY you can make Hanson's predictions accurate are to adjust the model AFTER THE FACT and even then it still significantly off, just not as insanely wrong as it otherwise would be.