Alexandra Witze writes about some new findings about humans' early climate meddling in Science News, saying "humans working the land put nearly 350 billion metric tons of carbon...into the atmosphere by the year 1850." She puts these numbers in context:
For comparison, between 1850 and 2000 people added 440 billion tons of carbon, mostly from burning fossil fuels — surpassing in a century and a half what had previously taken humankind eight millennia.
The video above tracks the change in land use over the past eight millenia. You can watch the land use changes spread from Mesopotamia and the Fertile Crescent out to India and Northern China, to Europe in Classical times, and on.