I agree with that. But, as you see from Geoff's post, even the climate scientists who write articles on the "Worst case" of Methane release have simply not thought about what it would mean, purely locally, for a large scale release.
In fact the RC article I linked talked about 100 times background being a "worst case" and yet we see from Oden that we are already getting up to 50 times background. OK he talked about 100 times for 100 years. But only for the lakes. So if we get 20 from the lakes and 80 from the clathrates, what then?
If it then doubles, or triples? What then? Nobody knows because nobody has seen how it destabilises in the current environment.
Part of what is going on here is a conversation that has occurred frequently in the history of science, and described as a conflict of paradigms - Uniformitarianism vs Catastrophism.
During the emergence of Geology as a clearly separate natural science in the 18th century, this first played out as a conflict between theologically driven presumptions of time frame (universe built in 7 days, the world only ~8000 years old), and the calculations of James Hutton, who by studying sedimentation rates in Scottish watersheds made the astonishing assertion the world may be 100's of millions of years old.
We now live in an age where Uniformitarianism is the dominant paradigm, but not rigidly so. Some events - like early 20th century Geologists J Harlan Bretz describing massive glacial outbreak flood events such as created the terranes in the Pacific Northwest - have challenged how we think about events and timeframes again.
We are moving into a more balanced Paradigm; one that is more dynamic and accepts that data may take us to unusual conclusions, which are driven by greater understanding of chaos and probability in systems.
So, actually, I think I can disagree with one assertion you make here - that science hasn't been thinking about sudden changes in various GHG concentrations. I'd say over the last decade or so its been rather obsessed with it. That a "catastrophic" hypothesis for methane release hasn't emerged isn't the result of a systemic oversight on the part of science. Rather, that catastrophic hypothesis hasn't emerged, because our understanding of systems and the data we are gathering doesn't support it.
Now, let's also put "catastrophic" in quotes here, because that perception is driven by time frame; in Uniformitarian, Geological terms,
Everything going on with the Arctic and GHG is catastrophic.
Nobody is talking about "clathrate gun hypotheses" or runaway impacts. What we are talking about is strictly short term, local, impacts to a system which is already under stress. It does not need 1C extra warming or 2C extra warming to have a massive impact. The system is already seeing >10C warming in winter and, roughly, >3C warming in summer.
Actually, without putting too fine a point on it, you just did previously in this comment; you are suggesting sudden catastrophic change to the system via localized releases of methane.
Breaking down your argument a bit here, looking at your citation of the climate changes across latitude, you over look a key factor. Those thermal changes are the result of energy budget changes across the entire globe as a system, not localized changes in GHG concentration.
All we are postulating is the knock on impact, locally, of a local hot spot of warming, which may generate methane which will rapidly destabilise the ice under threat.
I'm sure that is not something we want to ignore by looking at decadal "global" patterns of methane emissions.
Let's start by putting that "hot spot" warming into perspective, as I think that might put the over all argument to rest with a thought experiment.
Relying on the specific articles and discussion you cited earlier, the most generous estimates of the forcing from Methane runs to about 5 watts/M2/Second; this is the current number, at our current levels of concentration. Using this as our base, let's be similarly generous and presume a prompt local tripling of concentration of Methane to give us an additional 10 watts/M2/Second.
The first challenge applying this heat to the ice is the challenge of transport. During the melt season far and away the driving force is insolation, applied indirectly via heating of sea and melt water, and directly via energy which bypasses albedo and gets picked up by the ice.
Conductive heating via transported energy, either from currents or overturn in the water column is the second most prominent force.
Transfer via direct atmospheric transfer is a distant third.
Most of the immediate impact of the Methane would be atmospheric, by way of heating the gas itself, and a significant portion of that would be in the mid to upper troposphere. The fraction which would most directly affect ice (or surrounding water) would be re-radiation of that fraction of heat directed down towards it from the atmosphere.
Being generous again, and presuming
all of that 10W/M2/S went the right way, the net prompt increase in heat applied to ice only increases the total energy budget by less than 2 percent (10W/M2/S of Methane forcing vs 400W/M2/S from sunlight).
Now, don't get me wrong, over annual scales, this would be a huge additional load on a system which already is approaching forcing limits. However short term - days to weeks - which is the longest the time frame the effects on concentration a "prompt" release of methane would last, the impact would be trivial, amounting to only enough energy to melt a few CM of ice at most.
In fact, my thinking more and more is, that if we want to examine what the most significant impacts of GHG are on the arctic, we need to look at the refreeze rather than the melt. By definition, GHG's are inhibiting the export of energy from the system, not applying more energy to it. We put more blankets on the bed, less heat gets out of it. QED, the increased energy budget in the system makes the release of heat (via crystallization) more difficult, reducing the rate at which the ice forms, and reducing the maximum thickness it can achieve without ridging.
So in summary, my conclusion is that while sudden release might be dramatic, even in the idealized conditions you are imagining, the prompt effect of massive methane release on ice would not be significant.
