This continues the discussion of the asymmetric distribution of carbon dioxide as it is mainly produced in the northern hemisphere and over the course of time mixes with the atmosphere in the southern hemisphere

 

 

This 'rug' diagram shows the main features of the way in which CO2 has built up in the atmosphere over the last ten years. It shows the gradual annual increase in CO2 concentration and the seasonal changes, these being the subject of the next page.

There is a definite boundary at the equator which is consistent with the known mixing rates in the hemispheres. Mixing of injected gases in either hemisphere occurs in about three months, but N/S interhemispheric mixing takes about another 12 months.

The next diagram is a 'snapshot' of the concentration of CO2 and shows in more detail where the gas is being generated.

   374                                               ppmv                                                         380

It is clear that the main sites for the generation of CO2 are the Eastern side of the US and the majority of Europe, Russia and China. A plume of the gas arises from the Congo region of Central Africa and is the result of wood burning. The diagram shows again the asymmetry of CO2 concentration between the two hemispheres.

Papers by Jos de Laat and A. N. Maurellis have concluded that there is a significant connection between surface temperatures and the extent of industrialization over the globe. They regard the effect on surface temperatures as being due to the local heating associated with industry rather than the radiative effect of the greater concentrations of CO2 in these regions. It is a possibility that there is a radiative connection. However transient the emission of CO2 in the vicinity of industrialized areas, there is the possibility that the terrestrial radiation from the surface would be absorbed in a thinner layer than otherwise and that there would be transient warming near the surface that would be greater than that expected for a well-mixed atmosphere. In other words, before the CO2 becomes well-mixed it exerts a greater warming effect and this could affect the temperature of the lower part of the troposphere in such regions sufficiently to affect the recorded temperatures that are fed into the global system that computes the annual temperature anomalies. This suggested connection has similarities to the above distribution of CO2 in the troposphere.

            A contested paper by Ernst Beck reported results of chemical analyses of air samples from around the world using chemical methods. These were inevitably those taken at ground levels in many laboratories and could have suffered from local transient higher-than-normal concentrations of CO2. Some recorded concentrations were of the order of 400 ppmv and the comment has been made that such values must have been local rather than representative of the global figure. The reason for this conclusion is that there would have had to have been a tremendous amount of CO2 present in the atmosphere to attain a global value of 400 ppmv. The reported values were measured in the 1940s when the ice-core values were much less and with values of around 300 ppmv. The difference, 100 ppmv, is equivalent to about 47 Gt C and for such an amount to enter the atmosphere over a short period and then disappear does not seem to be possible.

            Nevertheless, such transient local concentrations are to be expected around industrial areas and it is possible that while the concentration is high there is sufficient local warming to affect measurements at nearby weather stations.          

So, does global warming happen at all? That some warming is happening is not in much doubt, but it is asymmetric and not consistent with the model predictions. Of course, it could be that if there is global warming either from extra CO2 or from the various solar possibilities that the southern oceans are acting as a semi-global thermostat. More warming means more water vapour which is a negative feedback mechanism to keep temperature in check. The North Atlantic warm ocean current is also a candidate for causing the preferential warming of the Northern Hemisphere.

More discussion of the asymmetric distribution of warming is on page 53