De hoeveelheid CO2 in de atmosfeer stijgt sneller als tevoren.*
De laatste zes jaar is jaarlijks de hoeveelheid CO2 in de atmosfeer met ruim 4 miljard m³ toegenomen. Het huidige groeipercentage is het hoogste sinds het begin van de metingen in 1959 en veel hoger dan welke voorspelling ook. Deze stijging is het gevolg van drie factoren. Ten eerste is deze het gevolg van niet verwachte hogere CO2 uitstoot wereldwijd per dollar economische activiteiten. Deze was in de tachtiger en negentiger jaren gedaald doch is sinds 2000 duidelijk gestegen voornamelijk doordat veel nieuwe energiecentrales kolen als brandstof gebruiken. Ten tweede kunnen de oceanen, in het bijzonder rond de Zuidpool, steeds minder CO2 opnemen.
Verder zorgen grotere droogtes dat bomen en planten minder CO2 opnemen.
Rate Of CO2 Rise Accelerates
Economic growth and reduced uptake by ocean and land are responsible
Release of CO2 due to human activity is increasing faster than ever while "carbon
sinks"—CO2 uptake by oceans and land—are weakening, according to a new report (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.0702737104). These conclusions are based on an analysis of data from CO2-monitoring stations around the world.
Human activities such as burning fossil fuels, cement production, and tropical deforestation added a net average of 4.1 billion metric tons of CO2 (measured as carbon) to the atmosphere each year between 2000 and 2006, the study says. As a consequence, the CO2 concentration in the atmosphere rose 1.93 parts per million per year during this period to reach 381 ppm. In contrast, average CO2 growth rates were 1.58 ppm per year during the 1980s and 1.49 ppm per year during the 1990s.
The current growth rate "is the highest since the beginning of continuous monitoring in 1959," according to the report, whose lead author is Christopher B. Field, director of the Carnegie Institution's department of global ecology at Stanford University. Recent emission increases have been "above the spectrum of any of the scenarios described by the United Nations Intergovernmental Panel on Climate Change," he says.
The rapid rise in CO2 levels is primarily a result of three things, Field continues. First, the carbon intensity of the global economy has increased. Contrary to expectations, the amount of carbon, in kilograms, produced per dollar of global economic activity has risen recently, in contrast to the 1980s and 1990s, when the intensity fell. The intensity has gone up because most new power plants that have come on-line since 2000 are fueled by coal, the most carbon-intensive fuel, Field says.
Second, the ability of the oceans, especially the Southern Ocean near Antarctica, to absorb CO2 has declined, Field says. This conclusion is based on an analysis of data from Antarctic waters, which now have a higher concentration of carbon than in prior decades. And third, large droughts have reduced the uptake of CO2 by forests and other plants, he says.
"The new twist here is the demonstration that weakening land and ocean sinks are contributing to the accelerating growth of atmospheric CO2," Field
says. (November 2007)
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