Tin,
This is the nub of Skepticism.
Warmists and Skeptics acknowledge that CO2 is a green house gas, it is a scientific fact. To me a Denialist is a person who denies that CO2 is a GHG. I have yet to meet a Denialist, but I know large numbers of Skeptics and a few Warmists.
Global atmospheric warming can only occur if there is some increase in the atmospheres total thermal energy content. One mechanism of increase is that as atmospheric CO2 increases more thermal energy from the Sun is trapped in the atmosphere (CO2 attenuates re-radiation). Based on this concept, so long as CO2 is monotonically increasing then atmos. temp must increase monotonically, but
1. CO2 is a one-way street as an increase in CO2 cannot CAUSE cooling, or even pausing, only warming.
2. CO2 is a relatively weak GHG and to explain the rapid rise in temp over the last century it is necessary to invoke 'multiplying factors'.
A perfectly valid multiplying factor is H2O (also a known GHG), so an increase in CO2 causes a slight rise in temp which evaporates water and raises atmospheric humidity which traps more heat, but
1. it is not possible to measure the global average atmos moisture content
2.. so computer modelling uses dTatm = dTco2 / (1-G), so if G=0.5 it predicts dTatm increases 2 x as much if increase was due to CO2 alone (which can be calculated exactly so long as you know its conc.).
Now just tweak G so dTatm calculated by model = dTobs measured by weather stations, but
1. H2O is also a one-way street ...
To have global temp pause (current) or decline (mid 20C) then some thermal energy (mistakenly referred to as HEAT) must be taken out of the atmosphere and the only mechanisms are
1. increase ocean temp
2. melt some ice
Again both perfectly valid mechanisms, but both MUST result in changes in the rate of increase in sea level (thermal expansion and more water resp.) BUT the record of sea level change shows that the rate of increase is constant not variable
http://notalotofpeopleknowthat.wordpress.com/2012/05/15/is-sea-level-rise-accelerating/
Consequently the only horse (anthropogenic CO2) in this one-horse-race falls at the last hurdle.
CONCLUSION - CO2 is part of the answer
RECOMMENDATION - At least get another horse - one that has a reverse gear as well as forward ... Its time to take a serious look at solar cycle intensity as a co-conspirator to anthropogenic CO2.
