# Controversies in Science/Are humans causing global warming/A critique of A mathematical analysis of the divergence problem in dendroclimatology

(Review Paper) Cited in Controversies in Science/Are humans causing global warming/A critique of A mathematical analysis of the divergence problem in dendroclimatology

Divergences appear across much of the upper northern hemisphere but are not limited to there. The growth of trees reduced in response to warmer temperatures in Alaska after 1950, Canada and Siberia after 1970. It was also found that in tundra areas the photosynthesis rate increased and in the forest areas the photosynthesis rate decreased in a study that was done between 1982 and 2003. The decrease was most likely due to moisture limitations at higher temperatures. Another point that was made is that trees may experience a decrease sensitivity to temperature or a negative response to warming because of reasons such as draught, frost damage, seasonal temperature patterns change, or a change in snow pack. The decreased sensitivity changes the growth rate, this cannot be automatically associated with the climate changes.[1]

### Methods

Using a mathematical equation of r=mT+b (r=ring property, T=temperature, m&b = parameters) would provide a completely linear line on a graph, which is what has been assumed from the short calibration period they have to work with. However Loehle says there is no way this is possible! The graph would not be linear if all data was used. There are other contributing factors that play a role in the radius growth between tree rings from decade to decade. The mathematical equation they used to prove the linear line is neither reliable nor accurate.[1]

### Results

This proves that there are other environmental factors outside of climate changes that effect tree growth. The other factors are things such as draught, frost damage, change in seasonal temperature patterns, and change in snow packs. We cannot assume that an equation built off a short period of time equates to a linear line for decades to come. The equation is misleading. Environmental factors play a huge role in the diversions that occur within tree growth.[1]

This is a very good point. Archaeologists use dendrochronology to look at past environments, however it is a vague measurement. To conclude something like humans causing global warming, there would need to be much more evidence than just analyzing trees. Cthom4751 (talk) 17:28, 13 April 2012 (UTC)

## References

1. Loehle, C. (2008). A mathematical analysis of the divergence problem in dendrochronology http://icecap.us/images/uploads/Loehle_Divergence_CC.pdf