Development of the CO 2 latitude gradient in recent decades

Development of the CO 2 latitude gradient in recent decades Because 90% of the CO2 from fossil fuel combustion is emitted in the Northern Hemisphere, annual mean atmospheric CO2 mixing ratios are higher at middle and high northern latitudes than in the Southern Hemisphere. The observed CO2 latitude gradient varies interannually and has generally increased as fossil fuel CO2 emissions have increased. Back extrapolation of the measured CO2 latitude gradient to zero fossil fuel emissions gives a latitude gradient with the Northern Hemisphere lower than the Southern. A linear regression of Mauna Loa minus South Pole annual mean differences versus fossil fuel emissions for 1958 through 1996 gives a slope of 0.5 μmol mol−1 (abbreviated as ppm CO2) (Gt C)−1 (σ = 0.03) and an intercept (at zero fossil fuel emissions) of −0.8 ppm (σ = 0.2). Shorter data records yield similar results with larger uncertainties. We argue that this extrapolated gradient does not represent preindustrial conditions but is more correctly viewed as a decadal average gradient due to natural sources and sinks that underlie the anthropogenic perturbation. We interpret the extrapolated gradient as evidence for a contemporary Northern Hemisphere sink that has been proposed on the basis of other measurement and model approaches. The slopes (ppm CO2 per gigaton of C from fossil fuel burning) calculated from sufficiently long records tend to agree with model calculations based on fossil fuel emissions, suggesting that any trend in the Northern Hemisphere sink, during the period of the measurements, has been small relative to the trend in fossil fuel emissions. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Global Biogeochemical Cycles Wiley

Development of the CO 2 latitude gradient in recent decades

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Publisher
Wiley
Copyright
This paper is not subject to U.S.Copyright © 1999 by the American Geophysical Union.
ISSN
0886-6236
eISSN
1944-9224
DOI
10.1029/1999GB900045
Publisher site
See Article on Publisher Site

Abstract

Because 90% of the CO2 from fossil fuel combustion is emitted in the Northern Hemisphere, annual mean atmospheric CO2 mixing ratios are higher at middle and high northern latitudes than in the Southern Hemisphere. The observed CO2 latitude gradient varies interannually and has generally increased as fossil fuel CO2 emissions have increased. Back extrapolation of the measured CO2 latitude gradient to zero fossil fuel emissions gives a latitude gradient with the Northern Hemisphere lower than the Southern. A linear regression of Mauna Loa minus South Pole annual mean differences versus fossil fuel emissions for 1958 through 1996 gives a slope of 0.5 μmol mol−1 (abbreviated as ppm CO2) (Gt C)−1 (σ = 0.03) and an intercept (at zero fossil fuel emissions) of −0.8 ppm (σ = 0.2). Shorter data records yield similar results with larger uncertainties. We argue that this extrapolated gradient does not represent preindustrial conditions but is more correctly viewed as a decadal average gradient due to natural sources and sinks that underlie the anthropogenic perturbation. We interpret the extrapolated gradient as evidence for a contemporary Northern Hemisphere sink that has been proposed on the basis of other measurement and model approaches. The slopes (ppm CO2 per gigaton of C from fossil fuel burning) calculated from sufficiently long records tend to agree with model calculations based on fossil fuel emissions, suggesting that any trend in the Northern Hemisphere sink, during the period of the measurements, has been small relative to the trend in fossil fuel emissions.

Journal

Global Biogeochemical CyclesWiley

Published: Dec 1, 1999

References

  • Variations in modeled atmospheric transport of carbon dioxide and the consequences for CO 2 inversions
    Law, Law

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