Walter Cunningham explains it. "The fearmongers of global warming base their case on the correlation between CO2 and global temperature, even though we cannot be sure which is cause and which is effect. Historically, temperature increases have preceded high CO2 levels, and there have been periods when atmospheric CO2 levels were as much as 16 times what they are now, periods characterized not by warming but by glaciation. You might have to go back half a million years to match our current level of atmospheric CO2, but you only have to go back to the Medieval Warming Period, from the 10th to the 14th Century, to find an intense global warming episode, followed immediately by the drastic cooling of the Little Ice Age. Neither of these events were caused by variations in CO2 levels.Even though CO2 is a relatively minor constituent of “greenhouse gases,” alarmists have made it the whipping boy for global warming (probably because they know how fruitless it would be to propose controlling other principal constituents, H2O, CH4, and N2O). Since human activity does contribute a tiny portion of atmospheric CO2, they blame us for global warming. Other inconvenient facts ignored by the activists: Carbon dioxide is a nonpolluting gas, essential for plant photosynthesis. Higher concentrations of CO2 in the atmosphere produce bigger harvests." http://launchmagonline.com/index.php/Viewp...-not-Bliss.html