re: #854 Coracle

Source for that 5% number, please.

Earth’s climates have many buffers. It didn’t run away in the Cretaceous, either, but we had inland seas in what would become continental US. I’d rather not, thank you.

No. CO2 may not have initiated ancient warming cycles. But that is not applicable to the case today, when it is providing a clear forcing factor.

Simply false. The geologic and climate evidence does not support you.

The 5% number is commonly accepted. You can find it anywhere from Wikipedia to here: United Nations Environment Programme - World Meteorological Organization

“Carbon dioxide is released to the atmosphere by a variety of sources, and over 95% percent of these emissions would occur even if human beings were not present on Earth… carbon dioxide levels in the atmosphere would have changed little if human activities had not added an amount every year. This addition, presently about 3% of annual natural emissions…”

You still want to handwave away the “unknown cause” that started the previous warmings, yet have no problem accepting that once this warming started — without CO2 forcing — that 800 years later, the CO2 became the prime driver. And yet wave away again the “unknown cause” that stopped the warming and cooled the earth, allowing CO2 levels to fall again.

CO2 is considered a prime forcing agent today because the GCMs have been programmed to consider it as such. When one considers that there have been ice ages when CO2 content was as much as 10 times greater than today (the end of the Ordovician), and periods of decreasing CO2 when global temps were increasing (Silurian and Devonian), how can one presume that now CO2 is a major driver?

Perhaps you should research the historic geological data yourself and not just accept my — or anybody else’s — word for it.