[count-your-change]

“It's possible that other greenhouse gases such as methane could have contributed to the [PETM] warming,” Zeebe says. It's also possible that the models are underestimating the climate response to CO2 increases. If that's the case, it “would mean our understanding of the climate system is incomplete,” he says.”

OR maybe they are over estimating the effects of co2, but perish the thought since ignorance only works in one direction.

[Always Right]

OR maybe they are over estimating the effects of co2, but perish the thought since ignorance only works in one direction.

No kidding. That idea never once crosses their minds.

[brent13a]

If that's the case, it "would mean our understanding of the climate system is incomplete," he says.

That's the understatement of the decade!

[John Valentine]

Most likely the increase in atmospheric was the result of the temperature increase, not the cause of it.

The amount of CO2 stored in the worlds oceans dwarfs the amount of CO2 in the atmosphere, by maybe as much a 1000 to 1, and the oceans would have gassed off huge quantities of CO2 as a result of the increase in temperature. Warmer temperature reduces the ability of water to hold dissolved gases, like CO2.

[jnsun]

“It's possible that other greenhouse gases such as methane could have contributed to the [PETM] warming,” Zeebe says. It's also possible that the models are underestimating the climate response to CO2 increases. If that's the case, it “would mean our understanding of the climate system is incomplete,” he says.”

OR maybe they are over estimating the effects of co2, but perish the thought since ignorance only works in one direction.

Bingo!

Rephrased: "- It's also possible that the models are underestimating the climate CO2 response to CO2 climate temperature increases. If that's the case, it “would mean our understanding of the climate system is incomplete,” he says.” -"