[ExI] some inneresting comments of the Krugman graph

[Damien Broderick]

eg: in ref to

http://krugman.blogs.nytimes.com/2009/06/27/temperature-trends/

<Actually, what seems a better “model” to me is 
superimposing three trends: 1) A modest 
underlying warming trend as we crawl out of the 
centuries-long Little Ice Age (approx warming 
trendline seen 1850-1910), 2) An oscillating 
warming/cooling trend caused by shifts in 
AMO/PDO, and 3) a man-made warming trend which is 
very weak before 1900, weak until ~1940, stronger 
after 1940 due to both GHG emissions and land use 
changes. From 1910-1940 you get #1 positive, #2 
positive, #3 weakly positive for some pretty 
steep warming resulting in huge numbers of record 
highs from 1936-1944 or so. #2 goes negative from 
1940-1975, flattening or slightly overcoming the 
other trends. Then #2 goes positive again from 
1975-2002 with #3 more strongly positive than 
earlier in the century. Having all three positive 
from 1975-2002 made for steep, scary warming - 
but that’s not the real long-term trend, and at 
some point #1 is going to roll off - given the 
sun’s recent behavior, that may be starting to 
happen. Solar activity has been rising since the 
Maunder Minimum 350 years ago, but seems to be 
changing heading into SC24. If it’s peaked, that 
would be good news on the warming front.

If you “model” it that way, you definitely see 
that mankind has an impact - but it’s not driving 
everything. That makes sense, since we produce 
about 4% of the total global CO2 emissions each 
year, and CO2 is responsible for perhaps 3.5% of 
the total greenhouse effect. Multiply those 
together, and our contribution is modest unless 
you assume extremely high positive feedbacks in 
the system. Natural systems which have been 
stable to within +/- 3% or so over huge stretches 
of geologic time really cannot be dominated by 
positive feedbacks - we’d already either be an iceball or a fireball.
­ Mike Upham >





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