Somewhat depressing

Permafrost feedback update 2015: is it good or bad news?

Here's a good article summarising the present state of understanding of the risk from carbon leaking out of melting permafrost.  Long story short - catastrophic bursts of methane are still considered unlikely (despite craters found in Siberia), but the long term issue of carbon leaking as permafrost melts is still serious - like adding another United States' worth of emissions.

Scenarios like this make me wonder whether research should be more about carbon sequestration - not from carbon capture from burning fossil fuels, which should stop anyway, but capture and sequestration from the atmosphere.  The only serious method proposed for that is ocean fertilization, as far as I know.  I'm not sure that it has been looked into in enough detail...