Well I guess we could just store up the fuel and not burn it. That would be carbon negative. Or ship it to Mars and burn it there as a start to terra forming. Too bad it's hard to get stuff to Mars.

This is the answer. Not the mars thing, but creating fuel and not burning it. We got into this mess by taking stored up CO2 and releasing it for energy. You reverse this by taking energy and released CO2 and turning it into storable "fuel".

Would planting trees do the trick?

While it would certainly help, it would solve like 0.1% of the problem. Fun fact, plants actually consume oxygen at night. On a 24 hour cycle, they create more than they consume, so everyone just thinks all they do is create oxygen.

And we already have all the empty oil wells to pump the fuel back in.

One might wonder why we took something out, only to put it back in, but ours is not to question why.

I agree, the Clathrate Gun is firing right now. So we're probably going on the Big Temperature Roller Coaster Ride anyway. So in that sense carbon neutral is probably okay in the long run if we all survive right?