Re: CO2 tightly linked with climate for 420 million years

On Mar 28, 2:50 pm, Rodney Blackall <rblack...@xxxxxxxxxxxxxxxxxxxx>
wrote:
In article <1175106286.025077.151...@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Roger Coppock <rcopp...@xxxxxxxx> wrote:

" . . . climate sensitivity [to 2X CO2] greater than 1.5 °C
has probably the Earth's climate system over the past
420 million years, regardless of temporal scaling."

The trouble with going back so far into the past is that the geography of
Earth's surface has changed an awful lot in that time. If you disregard the
colossal oceanographic changes caused by the linking of the Pacific and
Atlantic; Arctic and Pacific and Arctic and Atlantic, let alone the building
of the great mountain ranges you could get some very unreal answers.

Good point, Rodney, a very good point.
Not only has the geography changed,
but the rotation period of the Earth,
and Solar irradiance change on very
long half a billion timescales like
this as well. How far back do you need
to go to show the CO2 to surface
temperature link? Do you need
historical data at all? Aren't the
direct measurements of CO2 forcing
enough?

.