Extremely interesting. I think Methane damage can be misleading in that it, as you mention, breaks down into CO2. Also, perhaps CO2 does not break down completely in a century. One source, cited below, suggests that 10% to 20% lingers far longer. Reference: http://www.globalwarmingart.com/wiki/Image:Carbon_Dioxide_Residence_Time_png

Concerning the Emian period (130kyrs to 116Kyrs) or the last interglacial period I noted the following research findings: “The abundance of spruce and alder pollen suggests, however, more northerly limits for forest vegetation zones during the Eemian than during the Holocene. Oak also grew closer to Lapland, indicating a wanner climate than during the Holocene climatic optimum.”

Firstly, Has it been established that we have reached the optimum temperature for this interglacial period? How could we possible know?

Secondly, it seems obvious to me that during the Emian period there would have been billions of trees and shrubs. These would have provided the negative feedback offsetting the lessor carbon uptake of warmer oceans. In addition these trees would have transpired enough to cause massive clouds and water vapour which would have tended to increase the albedo lost because of ice melting. I suggest that it has been this proliferation of organic growth that has caused Gaia to cool and head back into an ice age. Humans have destroyed the natural solution to increasing CO2.
Thus planting trees by the millions in previous permanent pastures world-wide is the best and least expensive solution. Meanwhile there must be a world-wide effort to compensate people for having far fewer children. Gaia cannot afford another 3 Billion people by 2050. I believe these two things are achievable NOW.

Best Wishes,

Sky McCain