Carbon dioxide (CO2)
is a greenhouse gas.
That means CO2
absorbs
electromagnetic
radiation, primarily
with a wave length
near 15 microns.
That was
demonstrated
in a laboratory
in the late 1800s.
But there is strong evidence
that CO2 has little, if any,
controlling effect on climate:
In the late Ordovician Period,
the planet plunged into
and then warmed up from
the Andean/Saharan ice age,
all at about 10 times
the current CO2 level
Over the Phanerozoic eon
(past 542 million years)
there is no correlation
between CO2 level and
average global temperature.
During the last, and previous,
peak glaciations, the temperature
trend changed directions before
the CO2 trend.
Since average temperature
has been directly and
accurately measured
world wide
( after 1940 for the
Southern Hemisphere ),
the global average temperature
had up, down, and sideways trends,
while CO2 trend has been only up.
Data from all reporting agencies
agree there has been little or no
sustained change in average
global temperature since about 2003,
in spite of a large CO2 increase
in that 15 year period, equal to
40% of the total CO2 increase
since 1800 !