In this work, methane representation in AM4.1 is improved by optimizing CH₄ emissions to match surface observations. We find increases in CH₄ sources balanced by increases in sinks lead to CH₄ stabilization during 1999–2006, and anthropogenic sources (e.g., agriculture, energy, and waste) are more likely major contributors to the renewed growth after 2006. Increases in CH₄ emissions and decreases in OH levels during 2008–2015 prolong CH₄ lifetime and amplify methane response to emission changes.