Modelling the seasonal contribution of a CO2 fertilization effect of the terrestrial vegetation to the amplitude increase in atmospheric CO2 at Mauna Loa Observatory

Abstract

The present detailed theoretical investigation shows that a pure CO2 stimulation of the net primary production may indeed lead to an amplitude increase of 0.15 plus 0.17% yr-1 and minus 0.10% yr-1 as compared to the measured value of 0.67 ± 0.25% yr-1 for the period between AD 1958 and AD 1987. Two other contributions to the seasonal cycle have been identified: 1) the seasonality of the fossil fuel consumption in the Northern Hemisphere is approximately in phase with the relative uptake or release of CO2 by the land vegetation and leads to a small contribution to the increase in amplitude, in the range between 0.01 and 0.08% yr-1; 2) the seasonally different transequatorial transport of fossil fuel carbon creates a seasonal behavior which again is approximately in phase with the biota and leads to an additional contribution in the range of 0 to 0.31% per year. -from Authors