Tuesday, November 14, 2006

Increasing carbon dioxide does not make forest grow faster

Even Prime Minister John Howard finally, finally conceding a carbon tax in the future doesn't stop Andrew Bolt from encouraging people to emit more carbon dioxide - to fertilise the world's forests.

Releasing carbon dioxide into the atmosphere spurs global warming. Trees absorb carbon dioxide.

In fact, they thrive on the stuff, and all this thriving and spreading was predicted.

Pedal to the metal, tree lovers!

Perhaps Andrew felt his logic exposed, because he felt the need to bolter it with annecdotal research. The pox vox:


Reader White Mouse reports:

My daughter works at a hydroponic farm where they actually pump CO2 into the glass houses because the plants grow faster and produce more fruit.

Hmm. Would that work on a global scale?

I wondered that myself, did some research, and dropped a debunk on his blog. I'm reposting it here because Andrew can be selective when publishing me.

Good question, Andrew - it's been looked into by:

Department of Ecology and Evolutionary Biology Princeton University.

Pacala, S.W., J.P. Casperson and M. Hansen. 2003. Forest Inventory Data Falsify Ecosystem Models of CO2 Fertilization. (Manuscript Abstract)

We analyze tree growth data from Wisconsin forest inventories completed in 1968, 1983, 1996 and 2002. These show that the rate of forest tree growth decreased steadily over the period, in contrast to the increases predicted by CO2 fertilization models. Measured growth rate changed an average of -0.27% y-1 (95% confidence range: -0.05% to -0.49% y-1), whereas the prediction for CO2 fertilization is 0.16% y-1 (corresponding to a ß of 0.36). The high statistical precision is due both to large sample sizes and positive inter-temporal correlations among the growth rates within the same plot. Decreased growth occurred in stands of all ages, and so our results are not caused by age-related declines in growth.


Neither the direct analysis of growth rates in Wisconsin, nor the re-analysis of the Michigan inventories is consistent with the CO2 fertilization model in Joos et al. (2002).

State-of-the-art ecosystem models of CO2 fertilization are evidently false for this region over the later third of the 20th century. We discuss the implications of this and other reasons for skepticism about the future magnitude of CO2 fertilization. In particular, the fossil fuel emissions reductions required to stabilize atmospheric CO2 at 500+50 ppm must begin decades sooner if the predictions of the CO2 fertilization models in the IPCC Third Assessment (Prentice et al. 2001) are incorrect. The difference between a terrestrial carbon sink that grows because of CO2 fertilization, and one that shrinks because it is caused by recovery from past land use, is the difference between the luxury of decades of delay and the need to act now.

[End abstract]

... and the answer is no, so we have even less time to reduce emissions than the IPCC previously thought .

The reason why forests are coming back is a direct result of conservation as a reading of your News article tells you.

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1 comment:

chalacuna said...

Global climate has never been this worst for the past 500 years. Based on scientific studies, harmful emmissions from plants, cars and other fuel burning machines are the major culprit to the rapid climate change. This phenomenon called global warming has been felt in several parts of the world and is noticable in the abnormal behavior of thyphoons and tidal waves.

it is everybodys responsiblity to help maintain the environment and save mother earth.

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