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Al Gore's Offsets Making Global Warming Worse

4:51 PM, Apr 19, 2007 • By BRIAN FAUGHNAN
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I know he meant well, but Al Gore might be making global warming worse:

Dr Bala and his colleagues took such effects into account using a computer model called the Integrated Climate and Carbon Model. Unlike most climate-change models, which calculate how the Earth should absorb and radiate heat in response to a list of greenhouse-gas concentrations, this one has many subsections that represent how the carbon cycle (photosynthesis and its consequences) works, and how it influences the climate. Thus, Dr Bala's model can be told to replace all the world's forests with shrubby grasslands, and left alone to work out how such a change would alter greenhouse-gas concentrations and how that, in turn, would influence the temperature in different places.

When Dr Bala ordered global clearcutting, the model calculated that the atmosphere's carbon-dioxide levels would roughly double by 2100. This is a much greater increase than happens in a business-as-usual simulation, but it would, paradoxically, make for a colder planet. That is because brighter high latitudes would reflect more sunlight in winter, cooling the local environment by as much as 6°C. The tropics would warm up, since they would be less cloudy, but not by enough to produce a net global heat gain. Overall, Dr Bala's model suggests that complete deforestation would cause an additional 1.3°C temperature rise compared with business as usual, because of the higher carbon-dioxide levels that would result. However, the additional reflectivity of the planet would cause 1.6°C of cooling. A treeless world would thus, as he reports in the Proceedings of the National Academy of Sciences, be 0.3°C cooler than otherwise.

I know that the argument is 'settled' because we have a 'consensus' and all, so it's surprising that counter-intuitive findings like this one pop up. (Or this one, which almost shrilly advocates pumping more CO2 into the atmosphere.) I thought scientists had already chased down all these minor effects (like solar cycles) that could be affecting our understanding of global climate change.

And before you say 'you're being silly; we can't cut down all the world's forests,' the study does say that carbon offsets might be making the problem worse:

...Carbon-offset outfits should take note of Dr Bala's paper. Planting trees in convenient places such as Europe and North America may actually be counterproductive. Instead, in an environmental two-for-one, it is the rainforests that need bolstering.

I wonder if--just maybe--we don't really understand climate change well enough to warrant radically changing our lifestyles.