BECAUSE the increase in the concentration of atmospheric carbon dioxide has correlated with an increase in the use of fossil fuels, causation has been assumed.
Tom Quirk has tested this assumption including through an analysis of the time delay between northern and southern hemisphere variations in carbon dioxide. In a new paper in the journal Energy and Environment he writes:
“Over the last 20 years substantial amounts of CO2 derived from fossil fuel have been released into the atmosphere. This has moved from 5.0 gigatonnes of carbon in 1980 to 6.2 gigatonnes in 1990 to 7.0 gigatonnes in 2000… Over 95% of this CO2 has been released in the Northern Hemisphere…
“A tracer for CO2 transport from the Northern Hemisphere to the Southern Hemisphere was provided by 14C created by nuclear weapons testing in the 1950’s and 1960’s.The analysis of 14C in atmospheric CO2 showed that it took some years for exchanges of CO2 between the hemispheres before the 14C was uniformly distributed…
“If 75% of CO2 from fossil fuel is emitted north of latitude 30 then some time lag might be expected due to the sharp year-to-year variations in the estimated amounts left in the atmosphere. A simple model, following the example of the 14Cdata with a one year mixing time, would suggest a delay of 6 months for CO2 changes in concentration in the Northern Hemisphere to appear in the Southern Hemisphere.
“A correlation plot of …year on year differences of monthly measurements at Mauna Loa against those at the South Pole [shows]… the time difference is positive when the South Pole data leads the Mauna Loa data. Any negative bias (asymmetry in the plot) would indicate a delayed arrival of CO2 in the Southern Hemisphere.
“There does not appear to be any time difference between the hemispheres. This suggests that the annual increases [in atmospheric carbon dioxide] may be coming from a global or equatorial source.”
Jennifer Marohasy BSc PhD has worked in industry and government. She is currently researching a novel technique for long-range weather forecasting funded by the B. Macfie Family Foundation.