The pre-industrial (Year 1850) to present-day (Year 2014) increase in methane from 808 to 1831 ppb leads to an effective radiative forcing (ERF) of 0.97±0.04 Wm^‑2 in the United Kingdom’s Earth System Model, UKESM1. The direct methane contribution is 0.54±0.04 Wm^‑2. It is better represented in UKESM1 than in its predecessor due to the inclusion of shortwave absorption, updates to the longwave spectral properties, and no interference from dust. An indirect ozone ERF of 0.13-0.20 Wm^-2 is largely due to the radiative effect of the tropospheric ozone increase outweighing that of the stratospheric ozone decrease. An indirect water vapor ERF of 0.07±0.05/0.02±0.04 Wm^‑2 is consistent with previous estimates based on the stratospherically-adjusted radiative forcing metric. The methane increase also leads to a cloud radiative effect of 0.12±0.02 Wm^‑2 from aerosol-cloud interactions and thermodynamic adjustments. The aerosol-mediated contribution (0.28‑0.30 Wm^‑2) arises because methane-driven oxidant changes alter the rate of new particle formation (-8 %), causing a change in the aerosol size distribution towards fewer larger particles. There is a resulting decrease in cloud droplet number concentration and an increase in cloud droplet effective radius. There are additional shortwave and longwave contributions of 0.23 and ‑0.35 Wm^-2 to the cloud forcing which are dynamically-driven. They arise from radiative heating and stabilization of the upper troposphere, resulting in a reduction in global cloud cover and convection. These results highlight the importance of chemistry-aerosol-cloud interactions and dynamical adjustments in climate forcing and can explain some of the diversity in multi-model estimates of methane forcing.