Back of the envelope calculations (4) An hour, six months, food and cars

coches+arboles

Sometimes I’ve heard girls complaining that sweets are like “ a minute in your mouth and a lifetime in your waist”. CO2 is a bit like that, but on the other side.
Some years ago we produced a technical paper for the Basque Government on climate change and urban planning. A fast calculation showed that in the current climate context of the Basque Country a hybrid car’s worth in CO2 emissions running at 110 km/h was equivalent to six months of carbon capture by a mature European beech. This back of the envelope figure was in fact more sophisticated, and based on several science documents including specific studies on the growth behaviour of different species and other factors. On the whole of the Basque Country (both a well forested and highly developed area by Spanish standards) forests were worth 2,9 million tonnes of CO2 capture by year, while the global regional emissions were some 20 million.
Back of the envelope calculations must be handled with care in climate change terms, as there are many confuse data, not always based on good will. Concisely, trees absorb CO2 to grow, and this CO2 goes to wood mass and in part to the soil; the metabolism of the plant defines how fast that plant grows, so a given species could have quite different behaviours as CO2 sink in Maine compared to Madrid or to Manila, as climate and soil qualities matter. In the end, buying car enticed by the fact that a tree will be planted to absorb that CO2 seems quite untrue; you could choose to drive just a few minutes a year, but I’m not sure this is the case. In the end, we are not that far from the kind of ad strategy also used for… cakes.

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