  Methane is thought to have been an important greenhouse gas during the
Archean, although its potential warming has been found to be limited at high
concentrations due to its high shortwave absorption. We use the Met Office
Unified Model, a general circulation model, to further explore the climatic
effect of different Archean methane concentrations. Surface warming peaks at a
pressure ratio CH$_4$:CO$_2$ of approximately 0.1, reaching a maximum of up to
7 K before significant cooling above this ratio. Equator-to-pole temperature
differences also tend to increase up to pCH$_4$ $\leq$300 Pa, which is driven
by a difference in radiative forcing at the equator and poles by methane and a
reduction in the latitudinal extend of the Hadley circulation. 3D models are
important to fully capture the cooling effect of methane, due to these impacts
of the circulation.
