I haven’t tracked down the specific evidence—but muons are comparatively easy:
They live long enough to leave tracks in particle detectors with known magnetic fields.
That gives you the charge-to-mass ratio. Given that charge looks quantized (Milliken oil drop experiment
and umpteen repetitions), and there are other pieces of evidence from the particle tracks of muon
decay (and the electrons from that decay again leave tracks, and the angles are visible even
if the neutrinos aren’t) - I’d be surprised if the muon mass wasn’t pretty solid.
Assuming that both particle physicists and climatologists are doing things properly, that would only mean that the muon mass has much smaller error bars than the global warming (which it does), not that the former is more likely to be correct within its error bars.
Then again, it’s possible that climatologists are less likely to be doing things properly.