Dendroclimatology

From Wikipedia, the free encyclopedia

Dendroclimatology is the science of extracting past climate information from information in trees. Initial work focused on measuring the tree ring width - this is simple to measure and can be related to climate parameters. But the annual growth of the tree leaves other traces, and in particular maximum latewood density is generally found to be a better indicator of temperature than ring width. It is, however, harder to measure. The technique is most useful in the temperate latitudes; the stable climate of tropical regions promotes continuous tree growth, eliminating growth rings. In regions such as the western U.S., dendroclimatology has proven exceedingly useful for reconstructing past climate.

Tree ring information can be used to reconstruct climatology at the growing site for certain seasons back thousands of years. It's possible to reconstruct records much older than the oldest living trees, either by using dead trees that are still in place (such as for old bristlecone pines), or even from trees that were cut and used for building long ago, provided one can correlate between rings from living and dead specimens.

In more recent times, the established connection between tree rings and climate appears to be breaking down. Briffa et al report in Nature, 1998:

During the second half of the twentieth century, the decadal-scale trends in wood density and summer temperatures have increasingly diverged as wood density has progressively fallen. The cause of this increasing insensitivity of wood density to temperature changes is not known...