Posts Tagged ‘Mauna Loa Observatory’

Unchanged seasonal variation shows that Carbon dioxide concentration increase is probably not due to fossil fuel combustion

May 5, 2013

Carbon dioxide concentration in the atmosphere varies seasonally with the May peak being about 6 ppm higher than the October low. These are very regular and are a reflection of biogenic and chemical interactions from plants, the soil and the oceans

This concentration is the net result following all the mechanisms by which carbon dioxide is produced and absorbed. Since 1960 the mean concentration has risen about 25% from about 320 ppm to just under 400 ppm now (399 as of yesterday) but the seasonal variation has remained virtually unchanged during this time.

from wikipedia

from wikipedia

This is not new and analyses the 25 year period from 1997 but I have only just come across it.


CO2 seasonal variation

CO2 seasonal variation

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.

The annual increase of CO2 in the atmosphere is in sharp contrast with the annual change in the seasonal variations (last 25 years)

The mean values are:
Annual CO2 increase = 1.572 ± 0.013 ppm per year
Seasonal CO2 increase = -0.001 ± 0.013 ppm per year

The general assumption is that about 40% of man-made carbon dioxide shows up as this increase with the remainder being absorbed by the enhanced action of sinks.

The justification for this conclusion is supported by measurements of the falling proportion of  13C  in the atmosphere which is taken to signal the appearance of CO2 from fossil fuel emissions. …… 

The correlation of changes in δ13C with ENSO events and the comparison with a simple model of a series of cascades suggest that the changes in δ13C in the atmosphere have little to do with the input of CO2 emissions from the continuous use of fossil fuels.

Even though the combustion of fossil fuels only contributes less than 4% of total carbon dioxide production (about 26Gt/year of 800+GT/year), it is usually assumed that the sinks available balance the natural sources and that the carbon dioxide concentration – without the effects of man – would be largely in equilibrium.  (Why carbon dioxide concentration should not vary naturally escapes me!). It seems rather illogical to me to claim that sinks can somehow distinguish the source of carbon dioxide in the atmosphere and preferentially choose to absorb natural emissions and reject anthropogenic emissions! Also, there is no sink where the absorption rate would not increase with concentration.

Carbon dioxide emission sources (GT CO2/year)

  • Transpiration 440
  • Release from oceans 330
  • Fossil fuel combustion 26
  • Changing land use 6
  • Volcanoes and weathering 1

Carbon dioxide is accumulating in the atmosphere by about 15 GT CO2/ year. The accuracy of the amounts of carbon dioxide emitted by transpiration and by the oceans is no better than about 2 – 3% and that error band (+/- 20GT/year)  is itself almost as large as the total amount of emissions from fossil fuels.



During the 1977 to 2001 time period analysed:
Changes in the isotope ratio are discontinuous. The temporal peaks in 13C appear to correlate with the CO2 concentration changes. Further the temporal peaks in 13C and the CO2 peaks correlate with ENSO events.
The yearly increases of atmospheric CO2 concentrations have been nearly two orders of magnitude greater than the change to seasonal variation which implies that the fossil fuel derived CO2 is almost totally absorbed locally in the year that it is emitted.
A time comparison of the SIO measurements of CO2 at Mauna Loa with the South Pole shows a lack of time delay for CO2 variations between the hemispheres that suggests a global or equatorial source of increasing CO2. The time comparison of 13C measurements suggest the Southern Hemisphere is the source. This does not favour the fossil fuel emissions of the Northern Hemisphere being responsible for ther observed increases.
All three approaches suggest that the increase of CO2 in the atmosphere may not be from the CO2 derived from fossil fuels. The 13C data is the most striking result and the other two approaches simply support the conclusion of the first approach.

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