Let me add one more quick thing... let's take a very simplistic look at what you just presented. If we take it at face value, we'd conclude that curbing methane production is where we should concentrate a healthy amount of our climate change energy. That certainly flies in the face of where the POLITICAL push has been. Given that the largest domestic producers of methane are landfills and livestock, it's simply not as "sexy" to talk about it. Which shows how the POLITICAL side of the "climate change" movement isn't really about good science.
Again this is completely oversimplified but meant to illustrate a valid point.