What concerns me is what will happen if/when mankind somehow manages to cut it's CO2 (plant food) emissions ... The earth is already adjusting to it by increasing the reproductive rate of plants, cyanobacteria and the like. If we cut CO2 emissions (or even significantly slow down it's steady increase) ... As relatively little is mankind's part in the whole CO2 emissions business, we might end up triggering an ice age since "global warming scientists" seem to think in terms of warming when CO2 levels are "high" (still well below the 1% or 10 000ppm range AFAIK) .... But what happens if we "succeed" in curbing down CO2 emissions and CO2 levels fall to historic lows ? As the current "theory" goes .... The more CO2 there is, the warmer it gets, the stronger the storms get etc ... I'd rather not trigger an ice-age by not thinking changes thru on both ways of the equation thank you very much... In other words, as far as I know nobody has come up with an "ideal" number of CO2 ppm's to this day.