While tropical forests exert a cooling influence on global climate, forests in northern regions exert a warming effect, researchers from the Lawrence Livermore National Laboratory reported in the April 17 Proceedings of the National Academy of Sciences.
The warming effect, the researchers added, is not merely trivial.
Predicted Increase 10º F
Based on the researchers’ computer modeling, forests above 20 degrees latitude in the Northern Hemisphere–that is, north of a line running through southern Mexico, Saharan Africa, central India, and the southernmost Chinese island of Hainan–will warm surface temperatures in those regions by an estimated 10º Fahrenheit by the year 2100.
Most of the warming is predicted to occur north of 50 degrees latitude –the line running just north of the U.S. border with Canada, through northern France, northern Mongolia, and southern Siberia.
As the researchers explained in their media release, forests affect climate in three ways.
First, forests decrease global temperatures by absorbing carbon dioxide from the atmosphere. Second, forests evaporate water into the atmosphere, which increases cloudiness and also helps cool the planet. Third, forests are dark and absorb more sunlight than most other types of land uses (the “albedo” effect), which warms the planet.
According to the new research, the effect of these phenomena in tropical forests is net cooling, while the effect of these phenomena in northern forests is net warming.
Causing Recent Warming?
The results of the study raise some interesting and potentially problematic questions.
How does the 10º warming caused by northern forests (many of which have been expanding in recent decades) fit into the picture of recent global warming? Could northern forests be a (or perhaps even the) major contributor to the supposed problem of global warming?
The new study casts doubt on eco-activist groups’ assertions that mid- and high-latitude timber harvests exacerbate global warming. ForestEthics, for example, claims, “Because the Boreal holds more carbon than any other terrestrial landscape, its conservation is imperative. Degrading the Boreal landscape threatens to transform the Boreal from one of the few healthy ‘lungs of the planet’ into a net climate destabilizer.”
In March of this year ForestEthics issued a report, “Robbing the Carbon Bank: Global Warming and Ontario’s Boreal Forest,” that alleged, “The logging of intact forests is one of Canada’s least recognized drivers of global warming.”
Having completely overlooked the albedo effect in its report, ForestEthics may have the net climate effect of Boreal forests exactly wrong. But the group continues to attack a variety of businesses for selling products made from Northern timber.
As a result of the ForestEthics campaign, companies such as Apple Computer, Dell Computer, Federal Express, Hewlett-Packard, Home Depot, IKEA, Johnson & Johnson, Kinko’s, Lowe’s, Nike, Office Depot, Staples, and Starbucks have pledged not to use timber from Northern forests.
ForestEthics’ most recent success came last December at the expense of Limited Brands, which was targeted with the group’s “Victoria’s Dirty Secret” campaign (Victoria’s Secret’s catalogs used paper made from Northern timber).
In light of the new Livermore National Laboratory study, environmental activists will have a more difficult time convincing people and businesses to plant trees or preserve forests as a means to offset global warming pressures.
Steven Milloy ([email protected]) publishes JunkScience.com and CSRWatch.com. He is also an adjunct scholar at the Competitive Enterprise Institute. This article was first published on Milloy’s JunkScience.com Web site, and is reprinted with permission.
For more information …
G. Bala et al., “Combined climate and carbon-cycle effects of large-scale deforestation,” Proceedings of the National Academy of Sciences, April 9, 2007, http://www.pnas.org/cgi/content/abstract/0608998104v1
ForestEthics, “Robbing the Carbon Bank: Global Warming and Ontario’s Boreal Forest,” March 2007, http://www.forestethics.org/downloads/globalwarming_2.pdf