Genghis the Green: Population Control By Any Means Necessary

Daily Mail

And this is how Genghis Khan, who repeatedly wiped out entire settlements, was able to scrub more carbon from the atmosphere than any other despot. 

‘We found that during the short events such as the Black Death and the Ming Dynasty collapse, the forest re-growth wasn't enough to overcome the emissions from decaying material in the soil,’ explained Pongratz

‘But during the longer-lasting ones like the Mongol invasion... there was enough time for the forests to re-grow and absorb significant amounts of carbon.’