Semiletov and Shakhova report

The methane researchers who disturbed our rest and inspired immediate, pre-communication debunking by Andrew Revkin, Semiletov and Shakhova, now explain their concerns to him based on the recent findings:

We would first note that we have never stated that the reason for the currently observed methane emissions were due to recent climate change. In fact, we explained in detail the mechanism of subsea permafrost destabilization as a result of inundation with seawater thousands of years ago. We have been working in this scientific field and this region for a decade. We understand its complexity more than anyone.  And like most scientists in our field, we have to deal with slowly improving understanding of ongoing processes that often incorporates different points of views expressed by different groups of researchers.

Yes, modeling is important. However, we know that modeling results cannot prove or disprove real observations because modeling always assumes significant simplification and should be validated with observational data, not vice versa. Much of our work includes this field validation. Last spring, we extracted a 53-meter long core sample from the East Siberian Arctic Shelf, to validate our conclusions about the current state of subsea permafrost. We found that the temperatures of the sediments were from 1.2 to 0.6 degrees below zero, Celsius, yet they were completely thawed. The model in the Dmitrenko paper [link] assumed a thaw point of zero degrees. Our observations show that the cornerstone assumption taken in their modeling was wrong. The rate at which the subsea permafrost is currently degrading largely depends on what state it was in when recent climate change appeared. It makes sense that modeling on an incorrect assumption about thaw point could create inaccurate results.

Observations are at the core of our work now. It is no surprise to us that others monitoring global methane have not found a signal from the Siberian Arctic or increase in global emissions. [This refers to the work of Ed Dlugokencky and others; see his comments in my Dot Earth post.] The number of stations monitoring atmospheric methane concentrations worldwide is very few. In the Arctic there are only three such stations — Barrow, Alert, Zeppelin — and all are far away from the Siberian Arctic. We are doing our multi-year observations, including year-round monitoring, in proximity to the source. In addition to measuring the amount of methane emitted from the area, we are trying to find out whether there is anything specific about those emissions that could distinguish them from other sources. It is incorrect to say that anyone is able to trace that signal yet.

All models must be validated by observations. New data obtained in our 2011 cruise and other unpublished data give us a clue to reevaluate if the scale of methane releases from the East Siberian Arctic Shelf seabed is assessed correctly (papers are now in preparation). This is how science works: step by step, from hypothesis based on limited data and logic to expanded observations in order to gain more facts that could equally prove or disprove the hypothesis. We would urge people to consider this process, not jump to conclusions and be open to the idea that new observations may significantly change what we understand about our world.

So what is the news here? The different thaw point result will need to be replicated. How far down the melt goes should be directly measured in as many locations as possible. Meanwhile, it should be trivial to do model runs at different thaw points and see what effect that might have.