I wrote about this thought experiment a long time ago. Now I have added a lot more. Since climate guys have no imagination, they can skip this. :)
So, we have a real earth, and since it is our earth, we have a number of dials we can twiddle. All of these dials have spun for real over geological time.
Climate guys don't appreciate that most of our earth's carbon has been swallowed by plate tectonics. Every once in a while, it all comes back, at a million times stronger than anything we can do. It's fun spinning this dial.
As well, a huge amount of water is down there with the carbon. It likes to come up with the carbon dioxide, but you can spin these things separately.
The continents come together or fling apart at a spin this dial.
This doesn't do much except freeze us. There must be a limit to dialing it up, or we'd be dead a long time ago. I think it's cheating to spin this one. :)
That's all I can think of right now. Next will be the fun of turning those dials up and down.
Oh yeah, for Christmas I want to leave the thought experiment, and get real ones. :) Look out for high-speed continents!