denman, one of the aspects overlooked by those stuck in the past claiming that the level of CO2 in the atmosphere was the "right" level is that perhaps, as you point out, it is not the right level for optimum plant growth. When pumping extra CO2 into closed systems does increase plant growth it should be obvious that the "natural" level in the atmosphere is actually too low. These same enclosed systems also require an increase of heat not only to optimise growth but to actually initiate it. Previous experience with SO2 emissions showed the the natural level of SO2 in the atmosphere was insufficient for optimum pasture growth, something that only became evident when restrictions on emissions resulted in decreasing production on the farmland affected. Like many things, all this was discovered by accident rather than by forward thinking researchers. Now we have self proclaimed experts telling us that the old fashioned levels of CO2 and tempertures are the optimum. Experience seems to indicate otherwise. Perhaps they should extract themselves from their old and tired ideas from the past and bring themselves up to speed.
