Tuesday, April 10, 2007

Carbon offsets trees the double edged leaf

As we have previously stated the use of forests as carbon offsets is not a simplistic solution as there are other factors that need to be identified,mostly latitude.

A new study attempts to resolve the factors that need to be quantified.


How effective are new trees in offsetting the carbon footprint? A new study suggests that the location of the new trees is an important factor when considering such carbon offset projects. Planting and preserving forests in the tropics is more likely to slow down global warming.

But the study concludes that planting new trees in certain parts of the planet may actually warm the Earth.

The new study, which combines climate and carbon-cycle effects of large-scale deforestation in a fully interactive three-dimensional climate-carbon model, confirms that planting more tropical rainforests could help slow global warming worldwide.

The research, led by Lawrence Livermore National Laboratory atmospheric scientist Govindasamy Bala, appears in the April 9-13 online edition of the Proceedings of the National Academy of Sciences.


Forests affect climate in three different ways: they absorb the greenhouse gas – carbon dioxide – from the atmosphere and help keep the planet cool; they evaporate water to the atmosphere and increase cloudiness, which also helps keep the planet cool; and they are dark and absorb sunlight (the albedo effect), warming the Earth. Previous climate change mitigation strategies that promote planting trees have taken only the first effect into account.

“Our study shows that only tropical rainforests are strongly beneficial in helping slow down global warming,” Bala said. “It is a win-win situation in the tropics because trees in the tropics, in addition to absorbing carbon dioxide, promote convective clouds that help to cool the planet. In other locations, the warming from the albedo effect either cancels or exceeds the net cooling from the other two effects.”


The study concludes that by the year 2100, forests in mid- and high-latitudes will make some places up to 10 degrees Fahrenheit warmer than would have occurred if the forests did not exist.

As the IPCC has stated in its 2007 publications its level of understanding of albedo is 10% and as we have seen with the photochemical modulation of SST by plankton,the biosphere is and important amplifier or attenuation mechanism of climate.

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