Towards reconstructing the Arctic atmospheric methane history over the 20th century: measurement and modeling results for the NGRIP firn. - Umezawa, Taku; Sugawara, Satoshi; Kawamura, Kenji; Oyabu, Ikumi; Andrews, Stephen J.; Saito, Takuya; Aoki, Shuji; Nakazawa, Takakiyo (Atmospheric Chemistry & Physics Discussions, 2021)