"There are lots of ways to deal with the Earth getting a bit warmer. God help us if those ice sheets ever start forming again."

If it doesn't seem like increasing the amount of CO2 would warm things up very much, maybe if you increased the amount of methane it could make some difference.

I believe current levels of methane is around 1750 ppb or 1.75 ppm. If you increased this level by 100 times- 175 ppm this might have some effect upon warming the planet.
There is no shortage of Methane in the oceans, but this would use up a lot of fuel- probably at least tens of billions of dollar worth.

Hmm.
If you consider methane cost per ton is somewhere around $300+ and you need 1 trillion tons [there is currently about 3 trillion tons of CO2 in the atmosphere at around 400 ppm]. It wouldn't represent a cost of tens of billions of dollar but rather hundreds of trillions of dollars. Hmm, pretty expensive. Plus the methane would only last for fairly short time in atmosphere- somewhere around a decade.

Now, if you only needed to double or triple the current levels of methane [instead of a 100 fold] you would only be using a couple trillion dollars worth of a resource- and actual cost of disturbing methane hydrate in the oceans- say in deposits which less easily minable [such as in deeper water or in smaller deposits] then that could be in the tens of billions range in terms of the operational costs.