2011-12-31 09:49:34Review of Schuur and Abbott 2011
Agnostic

mikepope_9@hotmail...
118.208.178.1

Review of the Schuur and Abbott commentary is here.

2011-12-31 09:59:32
Agnostic

mikepope_9@hotmail...
118.208.178.1

As a non-scientist, I am reluctant to be publicly critical of a Paper written by two scientists, so please be ctitcial of the above response.

Schuur and Abbott are both Bilogists but may well be knowledgeable of global warming and climate change issues.  It is also possible that they are writing outside their field of expertise.

2011-12-31 22:11:15
MarkR
Mark Richardson
m.t.richardson2@gmail...
134.225.187.225

The results they present seem reasonable, and they are the expert opinion of over 30 permafrost experts according to the article. Not the opinions of Schuur and Abbott...

 

I think the tone needs changing. Models are our predictors of the future, and our figures need checking. Perhaps contacting Schuur or Abbott to try and clear up the conclusion first is worth doing?

2012-01-01 05:04:32
Andy S

skucea@telus...
173.183.12.188

Agnostic:

I'm a bit pressed for time, so I can't do as much on this as I would like. Anyway, here goes...

1) Temperature increases. The temperature increases used by Schuur are increase from the 1985-2004 average, not pre-industrial. So, I don't think that they are low balls at all. The assumption of flat temperatures  after 2100 was a modelling what-if assumption to see the effect of 21st century temperature increases on permafrost emissions in later centuries, it was not a forecast.

2-5) I haven't done the calculations myself but I think it's safe to assume, in the mean time, that Schuur has got the arithmetic right. He's got 40 co-authors, it's published in Nature and the math is not that hard. The difficult part in doing it yourself is knowing what assumptions he used.  

The biggest sensitivity seems to be the proportion of methane among the emissions. If it doubled above the 2.7% that wouldn't seem unreasonable to me and that would increase the climate effect  substantially. However, the chemistry and biology of the processes of converting prrmafrost carbon to methane and carbon dioxide is a complex one that I don't think anyone understands fully, least of all me. So, I think, I'll defer to expert judgement on this.

6) I don't know why Schuur et al excluded the offshore permafrost from the discussion. It could be that that's not their speciality or perhaps they don't consider it significant. If you look at the  list of ~90 scientists in Schuur's group, there are are eight scientists from Fairbanks but not Shakhova or Semiletov. I have no idea why these two are not included. Wildly speculating, it could be S&S's choice, maybe the group is just specialized on onshore permafrost or it could be that S&S are considered renegades and are blackballed.

Schuur's overall numbers are not that different from the "bombshell" NSIDC/NOAA report earlier this year. The NN report forecast 100 billion tons of permafrost carbon by 2100, compared to 232-380 billion tonnes of CO2 equivalent by the same date. The Schuur worst case of 380 GT of CO2e would cause an atmospheric concentration increase of about 90 ppm of CO2e, which is a very big deal but not as bad as the ~700 ppm increase that we are expecting for the worst case A1FI emissions pathway from fossil fuels. The Schuur low case of 232 GT gives about 50 ppm atmospheric. So I think it's fair for Schuur to say that permafrost emissions will not "overshadow" fossil fuels. I don't think Schuur's case considers any increased boreal/Arctic uptake of carbon, through tree growth, which would reduce the net amount of C released from high latitudes.

I would not recommend publishing your comment as it stands. Why not instead send some questions to Schurr? His email address is at the end of the Nature article.

[Note I just changed by back-of-the-envelope atmospheric ppm esimates. I forgot the atmospheric fraction calculation.]

2012-01-01 16:26:59
Agnostic

mikepope_9@hotmail...
118.208.178.1

Thanks Andy

I have already sent my concerns to Ted Schuur - but so far no reply.  After all it is holiday-time  And I certainly would not dream of publishing before he gets back ti me.