The airborne fraction of carbon dioxide (CO2) has not increased either during the past 150 years or during the most recent five decades, research says.
That the fraction is increasing has been one of the key assumptions in atmospheric models that show increased man-made carbon emissions causing drastic changes in the earth’s climate.
Most of the CO2 emitted by human activity is absorbed by the oceans and our ecosystems. In fact, only about 45 per cent of emitted CO2 stays in the air, says the new study.
However, some studies have suggested that the ability of oceans and plants to absorb CO2 recently may have begun to decline.
Because understanding of CO2 fraction in air is important for predicting future climate change, it is essential to have accurate knowledge of whether that fraction is changing or will change as emissions increase.
Accordingly, Wolfgang Knorr of the department of earth sciences, University of Bristol in the UK, re-analysed available atmospheric CO2 and emissions data since 1850 and considered the uncertainties in the data.