I go back-and-forth with that data point. Because while that is measurable and does exist, there's also tons of data to the contrary.

Here: researchers argue that the “Genghis-Khan-caused global cooling” idea is overstated: the modeled CO₂ drop from Mongol-era depopulation is extremely small (far below what’s visible in ice cores), natural forces like volcanic eruptions and solar variability overwhelmingly dominate climate shifts of that period, population-loss estimates are highly uncertain, any localized reforestation would have been offset by land-use changes elsewhere, and no clear cooling signal appears in proxy climate records at the exact time of the Mongol conquests.