|naturalSCIENCE Home||Your Comment|
From Berlin, Alan Freeman reports in the (Toronto) Globe and Mail (April 11, 1998) on the reaction to a German Green Party proposal on gasoline taxes:
Meantime, on the business page, the Globe and Mail (April 10, 1998) published this from Reuters:
According to our research, the Dodge Durango:
Driven 20,000 km per year, a Durango consumes about three metric tons of fuel, and generates just under 10 metric tons of carbon dioxide. A fleet of one million Dodge Durangos (about 6 years' production at current rates) each driven 20,000 km per year would thus produce about 10 million tons of carbon dioxide per year. The Earth's atmosphere weighs just over 10 metric tons per square metre, or 5.5 X 1015 tons in total. A fleet of one million Durangos would thus raise atmospheric carbon dioxide concentration by about 2 parts per billion per year, assuming that there is no sink for the added carbon. That's a rather small increment relative to the current atmospheric carbon dioxide concentration of 350 parts per million (not billion). However, if we consider only the atmosphere above the United States, the carbon dioxide produced by a fleet of one million Durangos could, in a year, raise the carbon dioxide concentration by about 108 parts per billion--still not a lot.
However, if we take account of the other 150 million or so motor vehicles in the Unites States and assume that their fuel efficiency is twice that of a Dodge Durango, their annual output of carbon dioxide could raise the atmospheric concentration above the United States by 7.5 parts per million, or 2%. That is quite a lot if the effect is cumulative, as it would double atmospheric concentration in 50 years. But motor vehicles are not the sole or major source of carbon dioxide produced as a result of human activity. Other sources in the US exceed the output of motor vehicles by a factor of about three. Thus total US carbon dioxide production is sufficient to raise the atmospheric concentration above the United States by 8% a year.
Fortunately, not everyone produces as much carbon dioxide as the average American (although China, with a slightly smaller land mass, but a much larger population, is expected to pull far ahead of the US in aggregate carbon dioxide emissions within a few years). Moreover, two-thirds of the globe is covered by oceans, which, may, absorb, rather than emit, carbon dioxide. However, if every person on Earth produced as much carbon dioxide as the average American, global atmospheric carbon dioxide concentration could rise by more than 3 parts per million per year, sufficient, almost, to double the current atmospheric concentration within a century. However, the actual rate of change in atmospheric carbon dioxide concentration over the next 100 years is quite uncertain for three reasons.
First, of the carbon dioxide added to the atmosphere as a result of human activity, about half disappears. Some may be dissolved in the oceans, although ocean surface waters are already nearly saturated. Much more is probably absorbed by forests and other terrestrial ecosystems where photosynthesis and plant biomass accumulation appear to have been accelerated by the increases in global mean temperature and atmospheric carbon dioxide concentration that have occurred during the 20th century. Increased carbon dioxide concentration promotes plant growth primarily by improving the rate at which plants exchange atmospheric carbon for water during photosynthesis, thereby alleviating the restraint imposed on growth by drought.
However, it is uncertain that the current sinks for carbon dioxide will continue to operate. Trees have long life cycles. This means that forests cannot adapt to short-run changes in climate by changing their genetic make-up. Thus long-run adaptation of forests to rapid climate change may be preceded by widespread forest decline, which, by leading to the release of a large amount of biologically bound carbon, could accelerate a warming trend by enhancing the greenhouse effect. (The forest and the forest soil both contain an amount of carbon approximately equal to that in the atmosphere.)
Second, it is unclear what the long-term trend in human population will be. Estimates for the year 2100 vary from more than twice the present population to a number considerably less than the present population.
Third, it is impossible to predict how economic, technological, social, and political trends over the next 100 years will influence the use of forests, fossil fuels, and other resources. Thus, even if the changes in human population for the next 100 years were known, it would be impossible to predict for the same time-span how human activity will impact the environment. It remains to be seen, therefore, whether the world can survive the Dodge Durango and similarly inefficient people-moving products from General Motors, Ford, Toyota and Daimler-Benz, but the apparent trend to ever bigger and more powerful automobiles wants watching.
Your comment on this or any item in naturalSCIENCE is invited and should be addressed to: email@example.com. For further information on submitting a contribution to naturalSCIENCE, please see the Author Guide.
|naturalSCIENCE Contents||Top of Page|