Relax everyone - new NASA study says double CO2 no big deal

Your point is well taken.

Related to CH4, there's a post on Reaclimate that instantly and permanently changed my thinking about the strategy of "buying time" by addressing warming factors other than C02:

RealClimate: Losing time, not buying time

It's not directly relevant to your statement. Yet I thought I would bring it to your attention.

The point is that if we "buy time" by addressing short-lived forcings (CH4, soot, and so on) -- instead of addressing C02 (a large fraction of which is for all intents and purposes a permanent forcing) -- then in the long run we make things worse.

It's just logic: Trading off reductions in short-lived for long-lived forcings that have equivalent current impact will result in higher long-run impact.

Although the logic is trivial, it's a fairly deep point. For starters, it suggests that the entire IPCC method for counting GHGs (and, presumably, for crediting changes in emissions), based on a 100-year time window, may not be appropriate.

For another, if you believe that we won't see change until things get clearly and obviously bad, then postponing the day of reckoning by reducing short-lived factors but not C02 actually leaves our descendants worse off (because it delays the time at which we begin to throttle down C02 emissions).

There are caveats of course. If positive feedbacks (like those you mentioned) are large enough, then adoption of any means to slow warming may be beneficial. Or, if we get to the point where the impacts of warming exceed our ability to adapt, then ditto. But right now, where we're still comfortable but can see the probable train wreck that our descendants will face, I think I end up agreeing with the Realclimate posting. Trading short- for long-lived factors is just another way to allow us to remain comfortable at the expense of future generations.