I keep hearing that "most" of the observed global warming is man-made, but I think that is just short hand to avoid confusing the most casual audience, and it perhaps causes more misunderstanding than it avoids.
More than 100% of the warming is due to anthropogenic warming forcings. That is balanced by a hard-to-constrain anthropogenic cooling.
Whether the residual is even attributable to natural variability is not obvious to me; the residual may be dominated by adjustment transients and nonlinear couplings.
But is the residual a warming or a cooling? I think there is no evidence that we would be in a warming period had humans gone suddenly extinct in 1700 or so.
Natural forcing is basically volcanic and solar, right? Is there any evidence that these have been weighing on the warming side over the past century?
Skeptical science basically says no, by the way.
The only thing we can be sure of about the future is that it will be absolutely fantastic. So if what I say now seems to you to be very reasonable, then I have failed completely. Only if what I tell you appears absolutely unbelievable, have we any chance of visualizing the future as it really will happen.
- Arthur C. Clarke (h/t Brin)