[Buchal]

Does anyone on this thread know whether the ring thickness methods control for the fact that tree growth rates are not just a function of temperature, but also of the amount of CO2 in the air? (I.e., higher CO2 levels may produce thicker rings quite apart from any temperature change.)

[Thickman]

It is my understanding that it is commonly known that trees consume less and less CO2 as they grow older. That is why it is proposed that trees be cut and replaced with faster growing young trees in order to sequester more CO2 from the atmosphere.

For this reason I am certain that algorithms are used when analyzing tree rings for the purpose of reconstructing temperature records.

Of course none of this adds validity to the use of tree rings for generating historical data, let alone just 12 of them from someplace in Russia.

[slowhandluke]

Not only does extra co2 cause extra growth, but cooler but wetter years can cause more growth than warm but dry. It’s a real tricky thing to use tree rings as a proxy for temperature. I thought that was one of the things brought up in controversy with the Mann hockey stick curve.