CO2 is evenly distributed around the globe so that it is about 395ppm in the lower atmosphere.
The problem this creates for climatologists and the AGW theory is that it is hard to explain a difference being due to a constant.
Climate models are differential equations, a change in X leads to a change in Y.
Most of the warming over the last 100 years has occurred in the N Hemi, but the N Hemi is mostly land,
and there are many factors other than CO2 that could alter the climate and temperatures.
Roads and Cities create a known "urban heat island effect" which has absolutely nothing to do with atmospheric CO2.
The S Hemi however is mostly water and undisturbed by man, so it give a far better representation of the true natural climate
and any impact CO2 would have. The temperature increase in the S Hemi is only 3/4th that of the N Hemi.
Both N and S Hemi have equal CO2, so the higher temperature increase in the N Hemi can not be attributed to CO2,
it has to be due to something else. Constants can't cause changes, at least not in a differential equation.
Any real scientist would know this, and the N Hemi temperature data would be adjusted "controlling"
for the non-CO2 factors that increase the variability and magnification of the N Hemi temperatures.
Using the S Hemi as a true representation of temperatures undisturbed by man and yet subject to CO2 increases,
global temperatures have only increased 9/10th a degree C over the last 100 years, and most importantly the trend has remained essentially unchanged,
if anything the slope is flattening.