Methane (CH₄) emissions can be transported into the upper troposphere (UT) via the Asian monsoon anticyclone (AMA), driving CH₄ enhancements. Whether emissions or upward transport is the dominant factor remains debated. We analyzed UT CH₄ variability with AMA dynamics, finding strong ties between CH₄ distribution and the AMA's east–west oscillation. When centered near 80° E, vertical transport largely enhances CH₄ anomalies, with circulation effects 1–2 times greater than those of emissions.