Originally posted by mjp2
Why relative to 1950's levels? that's already stacking the deck relative to what we need to be talking about - rise above pre-industrial levels.
We're already a degree warmer. We've only got half a degree to work with. Maybe one more degree, but likely at significantly greater cost and risk. If you want to gamble on 1 then you are gambling on 6 also. And that's not pretty.
This is not a symmetrical risk analysis.
It's late enough over here and i am not intending to discuss this interminably. But your 150 years doesn't gel with the science.
I am open minded but i am not wasting time chasing rabbits down rabbit holes.
IPCC baseline for CO2 concentration change commences at 1950. You can take that up with them if you like.
http://www.ipcc-data.org/observ/ddc_co2.html
You say the 150 years period (ending 2100 as per IPCC climate models) doesnt gel, but you dont say why. I think perhaps you are just accidentally dribbling there and emitting the occasional NPC phrase "the science" to try to sound authorative. You have to explain why you think a number doesnt gel or you expose yourself to some potential ridicule as a blinkered nay-saying political activist rather than a scientist with an open mind IMO.
Using the IPCC's 1950 start date for CO2 concentration we expect to double 1950 CO2 levels by around 2100 according to scenario B1 and B2 - the optimistic scenarios based on lower end likely emissions. There is good reason why IPCC do not reference pre-industrial period talking about anomaly - the data is more sparse and uncertainty is greater if you go there. GISS use 1950-1981 as their reference period. Almost nobody except perhaps some cherry picking political extremist would use the end of LIA as the baseline for temperature change rather than period for which good data is available for most variables.
Sensitivity is expressed in temperature change per doubling. If ECS is really 6 degrees C per doubling then we may be narrowly avoiding entry into a mini ice age right now - we have gone from 310 to 410 ppm (+32% CO2) and seen only 1 degree of warming which must have been counteracted by very strong natural cooling forces to have been limited to this level of change. What happens if that unknown natural forcing accelerates or CO2 decreases due to misguided political activism in that scenario?
