Written by Jennifer Marohasy
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."
‘Sources and Sinks of Carbon Dioxide', by Tom Quirk, Energy and Environment, Volume 20, pages 103-119. http://www.multi-science.co.uk/ee.htm
The abstract reads:
THE conventional representation of the impact on the atmosphere of the use of fossil fuels is to state that the annual increases in concentration of CO2 come from fossil fuels and the balance of some 50% of fossil fuel CO2 is absorbed in the oceans or on land by physical and chemical processes. An examination of the data from: i) measurements of the fractionation of CO2 by way of Carbon-12 and Carbon-13 isotopes; ii) the seasonal variations of the concentration of CO2 in the Northern Hemisphere; and iii) the time delay between Northern and Southern Hemisphere variations in CO2, raises questions about the conventional explanation of the source of increased atmospheric CO2. The results suggest that El Nino and the Southern Oscillation events produce major changes in the carbon isotope ratio in the atmosphere. This does not favour the continuous increase of CO2 from the use of fossil fuels as the source of isotope ratio changes. The constancy of seasonal variations in CO2 and the lack of time delays between the hemispheres suggest that fossil fuel derived CO2 is almost totally absorbed locally in the year it is emitted. This implies that natural variability of the climate is the prime cause of increasing CO2, not the emissions of CO2 from the use of fossil fuels.
Data drawn from the website http://cdiac.ornl.gov/trends/co2/contents.htm .
Tom Quirk has a Master of Science from the University of Melbourne and Master of Arts and Doctor of Philosophy from the University of Oxford. His early career was spent in the UK and USA as an experimental research physicist, a University Lecturer and Fellow of three Oxford Colleges.