Ringer,

"OK: I accept that; but my argument is unaffected: I asked for evidence that human activity had affected climate, not that it had affected carbon dioxide & methane, which I accept."

Read again, and spend a bit of time understanding Figure 10. I believe it provides exactly the linkage you seek: human activity affected CO2 and CH4, CO2 and CH4 affected climate, ergo; humans affected climate.

Figure 10.

Then begin reading the references.