Trying to see the climate for the trees

Harvey Leifert in Environmental Research Web: Climate science has become the dismal science, according to Kevin Gurney of Purdue University, US. He promised to be “more depressing than Al Gore”, when he reported on recent and ongoing research to a gathering of science writers at the "New Horizons in Science" meeting late last year in Austin, Texas.

Biophysical feedbacks in the climate system are an emerging line of research that Gurney said has yet to be reported to the public. We always worry about carbon dioxide, “the big hammer in the system”, but biophysical processes are also involved. “We have never had the computational tools that would allow us to explore them, until recently,” he said.

Gurney presented results of model simulations in which researchers had stripped away all trees from three bands around the Earth: boreal latitudes, mid-latitudes, and the tropics.

There are lots of trees in boreal forests; the models show that on deforestation the increased reflectivity overwhelms the effect of the carbon dioxide released. Without boreal forests the Arctic, as well as temperate regions, would cool, because trees are very dark and absorb the Sun’s radiant heat. In their absence, the brighter snow-covered surface would reflect that heat back, causing cooling. This principle was known previously, said Gurney, “but we never really had proper coupled land–surface–atmosphere models with the sort of fidelity and computational power to explore this.” He characterized the results as “quite surprising”.

The tropics see the opposite effect. There, when you remove trees, you take away the source of water for the atmosphere, most of which is recycled from trees and formed into clouds. There is a three-stage “vicious cycle”,” said Gurney. Deforestation leads to reduced moisture, which leads to drought, which facilitates fire, which leads to more deforestation. Tropical deforestation results in warming all around the planet, and especially in the high latitudes, according to the model simulation….

The Tree of Life, from an etching by Athanasius Kircher, published in his Œdipus Ægypticus in 1652. This has since become the most common variant of the Tree used in Hermetic Qabalah.