My take on it if anyone cares:
We haven't been around long enough, nor do we have accurate enough information on the history of the planet, both in terms of its atmospheric composition, or its orbit.
Facts are though:
- Earth's distance from the sun regularly oscillates.
- Earth's axial tilt also undergoes periodic oscillations.
Both are very slight, but can still have an impact.
- We are producing more CO2 and other greenhouse gases than any other life form ever has, except perhaps for the massive colonies of bacteria that were the first lifeforms on the planet.
And a good bit of them died off when they would up creating an environment in which they couldn't survive - example, bacteria living in a oxygen-rich environment metabolize the oxygen. Eventually, all the oxygen is used, and they die, victims of their own success. Either that, or some die, until a balance is arrived at.
What I'm saying is, yes, this might be a natural warming trend. It might be good, it very well might not be. If it is a natural bad thing, it could be disastrous to help it along.