Since global warming entered the global lexicon, the scientific community has concluded that deforestation is one the primary causes of climate change. Subsequently, significant efforts to reduce or reverse warming trends have focused on reforestation throughout the world. However, a recent study published in the Proceedings of the National Academy of Sciences and reported in the Economist, suggests that these efforts may not result in the desired outcome. According to Dr. Govindasamy Bala of the Lawrence Livermore National Laboratory in California, planting trees everywhere might actually increase the earth’s temperature. Conversely, removing all the world’s trees could lead to global cooling.The reason for this counterintuitive conclusion is that trees affect the earth’s temperature in ways beyond the carbon that they sequester. Since forests tend to be darker than grasslands, even when covered in snow, they absorb more heat than other vegetative alternatives. This subsequently, leads to an increase in temperature. On the other hand, forests are more effective than other ecosystems at producing water vapor that creates cloud cover, which serves to reflect the sun’s heat back into space. This process cools the earth.
In an effort to account for these effects, Dr Bala developed the Integrated Climate and Carbon Model (ICCM). Unlike most climate change models, the ICCM goes beyond calculating how the Earth will likely absorb and radiate heat under different greenhouse gas concentrations. Dr. Bala’s model represents how the carbon cycle works and its influence on the climate. Therefore, the model can simulate how the earth’s temperature will respond to the replacement of all forests with grasslands, while still accounting for changes in greenhouse gas concentrations.
According to the model, global clearcutting would actually reduce the earth’s temperature by an estimated 0.3 degrees Celsius. The study indicates that the removal of the earth’s trees would double carbon dioxide levels by 2100, which would warm the globe by 1.3 degrees Celsius compared to business as usual. However, the increased reflectivity of the planet would result in a 1.6 degrees Celsius decrease in temperature, thus producing an overall cooling effect.
TreeHugger, of course, does not condone clearcutting the world’s forests, as there would be no trees left to hug. However, this study demonstrates the complexity of the challenges presented by climate change, and the various considerations that must be made in developing strategies to mitigate the effects of global warming.