Jim Cripwell
You raise a key question:
What is a “CO2 signal”?
A supporter of the CAGW premise might say: CO2 concentration has risen since measurements were installed at Mauna Loa in 1959, globally and annually averaged land and sea surface temperature has also risen since this period; since our models cannot explain this warming without attributing most of it to CO2 (plus some minor GHGs), we conclude that CO2 caused most of the observed warming, i.e. that is our observed “CO2 signal”.
Greenhouse theory tells us that CO2 is a GHG and that increased GHGs trap outgoing LW radiation, thereby leading to global warming. That is the theoretical justification for our “CO2 signal”.
The weak part of this argument is obviously the phrase “since our models cannot explain this warming without attributing most of it to CO2 (plus some minor GHGs)”, because this is an “argument from ignorance” – not “an argument from evidence”.
This is compounded by the fact that there was another (statistically indistinguishable) period of warming in the early 20th century, which the models cannot explain.
I’ve written this before, but it is the logic fallacy stated below:
1- Our models cannot explain the early 20th century warming
2- We know that most of the statistically indistinguishable late 20th century warming was caused by human GHGs (mostly CO2)
3- How do we know this?
4- Because our models cannot explain it any other way.
The “CO2 signal” remains a theoretically posited and computer generated “will o’ the wisp”.
Max
