Antarctica, traces of past pandemics in the ice - Earth and Poles. The first contacts between Americans and Europeans cause drops in CO2.
The human population has declined so much as a result of disease that many areas have likely been abandoned, allowing vegetation to regrow and absorb large amounts of carbon dioxide. “This corroborates scenarios of large-scale reorganization of land use in the Americas – comment the researchers – following contact between the New and Old Worlds”.