Claims of Long Life for Man's CO2 Emissions in Atmosphere are False

A post by Pehr Bjornbom discussing Gosta Pettersson's comments on the life of carbon isotopes in the atmosphere as CO2 shows that the model commonly used to predict the lifetime of man's CO2 emissions is seriously in error.  The Bern model for man's emissions is used in the many global climate models which my last post showed provided a very poor temperature prediction.  But C14 is a radioactive isotope of carbon that is produced in atmospheric atomic bomb tests.  Since those tests ended decades ago the C14 thrust into the atmosphere has diminished exponentially with time.  The concentration of the C14 over time is shown below in the graph and compared to the Bern model used in the climate models.

The x-axis is the time in years and the y-axis is the percentage of C14 compared to its start at 100%.  Note that the long dwell time of the Bern Model is entirely wrong.  In fact, the half-life of the C14 from this data appears to be about 10 years.  This is carbon that was thrust very high into the atmosphere.  There are also studies that claim that carbon dioxide generated at ground level has a shorter half-life than that deposited into the higher atmosphere.  These are all short lifetimes compared to the hundreds to thousands of years of the Bern Model.

One of the favorite arguments of the AGW alarmists is that man's emissions coming from the combustion of fossil fuels has less C13 isotope in it than the most common C12.  They use studies of the decreasing ratio of C13 to that of C12 in the air and in corals as shown below to argue that man-made CO2 emissions must linger a long time in the air and deplete the C13.

The argument is based on the idea that plants prefer C12 to C13.  If that is true, as more CO2 becomes available to plants in the air, will they not actually increase the ratio of C12 that they use to what they consider undesirable C13?  As they have more and more CO2 molecules to choose from, they can reject more and more of them having C13 in them.  Ocean absorption of CO2 from the atmosphere is also high, but the absorption of the less volatile CO2 molecules with the heavier isotope will be higher than that of molecules with only C12 in them.  So, the oceans with more CO2 molecules available for absorption will absorb more of the C13 and leave the atmosphere more and more short of C13.  These are dynamic situations.

There is even more to consider.  There are many natural sources of CO2 with varying concentrations of C13.  CO2 comes from deep sea vents and volcanoes as well.  It comes also primarily from the decay of vegetation in tropical areas and that source is low in C13.  In addition, any change in the flux of cosmic rays will change the amount of C13 created by cosmic radiation in the atmosphere.  Dr. Murry Salby recently showed that the higher concentration of CO2 in the atmosphere was primarily a consequence of a higher surface temperature and secondarily a function of the moisture of soil and is not substantially due to man's emissions.



An increase in atmospheric carbon dioxide causes plants to use more of it.  A recent study using satellite observations found that the rise in atmospheric CO2 caused an increase of foliage coverage in arid areas in Australia, North America, the Middle East and Africa by 11%.  This happens because higher CO2 concentrations allow plants to reduce their water use in the photosynthesis process.  This adds to the complex dynamic response of the sources and sinks for CO2 concentrations in the atmosphere. 

The idea that C13 ratios to C12 tell us a simple story about man's emissions dwell time in the atmosphere is clearly simple-minded and wrong.  We know this from the atomic bomb test data on C14, which plants also discriminate against in favor of C12.  We know this from the results of Dr. Murry Salby.  The much bally-hoed carbon cycle is not well-known and settled science despite the claims of the catastrophic anthropogenic global warming alarmists.