Land clearance has been going on for tens of thousands of years by man. The earliest probably being when 90% of Australia's forests was permanently cleared by the Aborigines about 60,000 years ago. The ME was cleared by the Sumerians to fuel their copper smelting resulting in the desert there, and there was probably a similar occurrence that caused the Sahara. The CO2 levels have remained within the 320 to 420 band since then - 420 in 1815, btw.
