We know that certain things trap heat. We can test that very easily. In the case of at least one greenhouse gas, you yourself probably confirm this every day without even realizing it.
We know that we are pumping billions and billions of tons of these heat-trapping gases into the atmosphere.
We know that, as we have done this, global temperatures have increased.
Now, imagine that you heated an oven, put a pie in it, took it out an hour later and said, "Look, I baked a pie!"
Then someone else came along and said, "Hold on, now! We don't know what happened to that pie. Maybe the sun got hotter! Maybe the poles shifted and this has something to do with the magnetosphere! Maybe this sort of thing just happens!"
But the sun didn't get hotter while it was baking. Compasses still point north for the time being, and when they no longer do, that won't bake a pie. This sort of thing doesn't just happen. And the very few experts that they can point to for support tend to be employed by businesses with a financial interest in making people believe that ovens don't bake pies. (Sometimes even secretly.)
So, would you call that person a "skeptic"? Would you believe that their views are worthy of respect and should be given equal weight? Would you think that person is smarter and more informed than all of those arrogant so-called experts who believe that ovens really do bake pies?
How you would see that person is pretty much exactly how reasonable people see you. Except that the pie guy isn't trying to bake the entire world.