McGuire, A.D., Koven, C., Lawrence, D.M., Clein, J.S., Xia, J., Beer, C., Burke, E., Chen, G., Chen, X., Delire, C., Jafarov, E., MacDougall, A.H., Marchenko, S., Nicolsky, D., Peng, S., Rinke, A., Saito, K., Zhang, W., Alkama, R., Bohn, T.J., Ciais, P., Decharme, B., Ekici, A., Gouttevin, I., Hajima, T., Hayes, D.J., Ji, D., Krinner, G., Lettenmaier, D.P., Luo, Y., Miller, P.A., Moore, J.C., Romanovsky, V., Schadel, C., Schaefer, K., Schuur, E.A.G., Smith, B., Sueyoshi, T. and Zhuang, Q. 2016. Variability in the sensitivity among model simulations of permafrost and carbon dynamics in the permafrost region between 1960 and 2009. Global Biogeochemical Cycles 30: 1015-1037.
Introducing their study, McGuire et al. (2016) write that "a significant portion of the large amount of carbon (C) currently stored in soils of the permafrost region of the Northern Hemisphere has the potential to be emitted as the greenhouse gases CO2 and CH4 under a warmer climate." And, therefore, they go on to evaluate "the variability in the sensitivity of permafrost and soil carbon in recent decades among land surface model simulations over the permafrost region between 1960 and 2009," during which time the planet warmed considerably.
Of the 15 models that the 39 researchers studied in this regard, they found that (1) between 1960 and 2009 all of the models predicted a loss of near-surface permafrost area over the region. But they note that (2) the scatter among the model predictions was humongous, ranging from 0.2 to 58.8 x 103 km2 per year. In addition, they report that (3) "all of the models indicate that both vegetation and soil C storage have increased by 156 to 954 Tg C yr-1 between 1960 and 2009 over the permafrost region," even though (4) "model analyses indicate that warming alone would decrease soil C storage."
In further discussion of this perplexing situation, McGuire et al. note that (5) "increases in gross primary production (GPP) largely explain the simulated increases in vegetation and soil C," while adding that (6) "the sensitivity of GPP to increases in atmospheric CO2 was the dominant cause of increases in GPP across the models," and that (7) a comparison of simulated GPP trends across the 1982-2009 period with that of a global GPP data set indicates, sadly, that (8) "all of the models overestimate the trend in GPP."Posted 10 January 2017