As Laurent can handle more feedback factors not fully accounted for in AR5, I offer the following partial listing
:
1. The following linked reference indicates that the addition of forcings are generally non-linear resulting in larger radiative forcing than most models assume that are used to advise policymakers:
http://www.earth-syst-dynam.net/4/253/2013/esd-4-253-2013.htmlThe sensitivity of the modeled energy budget and hydrological cycle to CO2 and solar forcing by: N. Schaller, J. Cermak, M. Wild, and R. Knutti; Earth Syst. Dynam., 4, 253–266, 2013;
www.earth-syst-dynam.net/4/253/2013/; doi:10.5194/esd-4-253-2013
2. The following linked two references discuss the positive feedback caused by the acidification of the oceans reducing sulfur flux from the ocean which then results in more radiative forcing than considered in AR5:
http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1981.htmlGlobal warming amplified by reduced sulphur fluxes as a result of ocean acidification; Katharina D. Six, Silvia Kloster, Tatiana Ilyina, Stephen D. Archer, Kai Zhang & Ernst Maier-Reimer; Nature Climate Change; (2013); doi:10.1038/nclimate1981
http://www.mpimet.mpg.de/nc/en/communication/news/single-news/article/climate-change-ocean-acidification-amplifies-global-warming.html3. The following linked reference discusses the risk of decades-old carbon being emitted into the atmosphere due to global warming. This could be a significant positive feedback factor (that has not been included in most models yet) if the world stays on the BAU path that it is currently following:
http://www.pnas.org/content/early/2012/06/07/1120603109.abstractWarming accelerates decomposition of decades-old carbon in forest soils;
by: Francesca M. Hopkins, Margaret S. Torn, and Susan E. Trumbore; PNAS June 11, 2012; doi: 10.1073/pnas.1120603109
4. The linked reference indicates that there is considerable uncertainty in the amount of potential CO₂ contribution to the atmosphere from Soil Organic Carbon (SOC) particularly under RCP 8.5, and greater uncertainty means greater risk:
http://www.earth-syst-dynam-discuss.net/4/1035/2013/esdd-4-1035-2013.htmlNishina, K., Ito, A., Beerling, D. J., Cadule, P., Ciais, P., Clark, D. B., Falloon, P., Friend, A. D., Kahana, R., Kato, E., Keribin, R., Lucht, W., Lomas, M., Rademacher, T. T., Pavlick, R., Schaphoff, S., Vuichard, N., Warszawaski, L., and Yokohata, T.: Global soil organic carbon stock projection uncertainties relevant to sensitivity of global mean temperature and precipitation changes, Earth Syst. Dynam. Discuss., 4, 1035-1064, doi:10.5194/esdd-4-1035-2013, 2013
5. The linked reference indicates that terrestrial vegetation will stop acting as a carbon sink after a 4 degree C mean global surface temperature rise, while this high degree of climate sensitivity is not captured by most GCMs:
http://www.pnas.org/content/early/2013/12/12/1222477110Andrew D. Friend, Wolfgang Lucht, Tim T. Rademacher, Rozenn Keribin, Richard Betts, Patricia Cadule, Philippe Ciais, Douglas B. Clark, Rutger Dankers, Pete D. Falloon, Akihiko Ito, Ron Kahana, Axel Kleidon, Mark R. Lomas, Kazuya Nishina, Sebastian Ostberg, Ryan Pavlick, Philippe Peylin, Sibyll Schaphoff, Nicolas Vuichard, Lila Warszawski, Andy Wiltshire, and F. Ian Woodward, 2013, "Carbon residence time dominates uncertainty in terrestrial vegetation responses to future climate and atmospheric CO₂", PNAS December 16, 2013, doi: 10.1073/pnas.1222477110
6. The linked reference provides the first evidence that as water vapor invades the stratosphere it is serving as source of a significant positive feedback mechanism (which in not fully modelled by most GCMs):
http://www.pnas.org/content/early/2013/09/26/1310344110.abstract?sid=8069b689-eb9f-44f1-8e4e-13e764b3d5fcA. E. Dessler, M. R. Schoeberl, T. Wang, S. M. Davis, and K. H. Rosenlof, (2013), "Stratospheric water vapor feedback", PNAS, doi: 10.1073/pnas.1310344110
7. The linked reference (with a free access pdf) indicates that the albedo of both melting snow and ice are affected at least two times more adversely than non-melting snow and ice by black carbon. Therefore, as the polar areas continue warm-up the positive feedback from black carbon will likely increase:
Marks, A. A. and King, M. D.: The effect of snow/sea ice type on the response of albedo and light penetration depth (e-folding depth) to increasing black carbon, The Cryosphere Discuss., 8, 1023-1056, doi:10.5194/tcd-8-1023-2014, 2014.
http://www.the-cryosphere-discuss.net/8/1023/2014/tcd-8-1023-2014.html8. The following linked research indicates that emissions of methane of biological origins increase rapidly with increasing warming, even on a seasonal, or ENSO, basis:
Gabriel Yvon-Durocher, Andrew P. Allen, David Bastviken, Ralf Conrad, Cristian Gudasz, Annick St-Pierre, Nguyen Thanh-Duc & Paul A. del Giorgio, (2014), "Methane fluxes show consistent temperature dependence across microbial to ecosystem scales", Nature, Volume: 507, pp: 488–491, doi:10.1038/nature13164
http://www.nature.com/nature/journal/v507/n7493/full/nature13164.html9. The linked reference makes it clear that the boreal forests (in the taiga, see the attached image for the extent) are at greater risk of destruction than previously realized, most significantly due to the thawing of the permafrost, which promotes fires, droughts and insect attack. Not only would this destruction turn a large CO₂ sink into a CO₂ source, but would also eliminate a major source of aerosols emitted by the boreal forests which facilitate cloud formation (which reflects sunlight and reduces global warming):
Moen, J., Rist, L., Bishop, K., Chapin, F. S., Ellison, D., Kuuluvainen, T., Bradshaw, C. J. (2014), "Eye on the taiga: removing global policy impediments to safeguard the boreal forest", Conservation Letters, DOI: 10.1111/conl.12098
http://onlinelibrary.wiley.com/doi/10.1111/conl.12098/abstract10. The linked reference indicates that methane emissions from livestock is greater than previously thought, and with meat consumption in Asia increasing rapidly, the coming increases livestock will contribute to increasing atmospheric methane concentrations:
Wecht, K. J., D. J. Jacob, C. Frankenberg, Z. Jiang, and D. R. Blake (2014), Mapping of North American methane emissions with high spatial resolution by inversion of SCIAMACHY satellite data, J. Geophys. Res. Atmos., 119, doi:10.1002/2014JD021551.
http://onlinelibrary.wiley.com/doi/10.1002/2014JD021551/abstract11. The linked article about current Canadian wildfires indicate that the current weather pattern contributing to the wildfires were not predicted by the GCMs to occur for another 40-yrs:
http://www.adn.com/article/20140717/worst-wildfire-season-decades-canada-s-northwest-territories12. The linked article (with a free access pdf) indicates that as global temperatures increase, methane emissions from peat bogs will also increase:
van Winden JF, Reichart G-J, McNamara NP, Benthien A, Damsté JSS (2012) Temperature-Induced Increase in Methane Release from Peat Bogs: A Mesocosm Experiment. PLoS ONE 7(6): e39614. doi:10.1371/journal.pone.0039614
http://www.plosone.org/article/info:doi/10.1371/journal.pone.003961413. The linked reference indicates that the Earth System Sensitivity, ESS, may be bigger than previously thought; however, it does not indicate how quickly the positive feedback from the synchronization of the North Pacific and North Atlantic climates:
Summer K. Praetorius, Alan C. Mix, (2014), "Synchronization of North Pacific and Greenland climates preceded abrupt deglacial warming", Science 25 July 2014: Vol. 345 no. 6195 pp. 444-448 DOI: 10.1126/science.1252000
http://www.sciencemag.org/content/345/6195/44414. The linked reference found that aerosol-cloud associated changes in the amount of the clouds and changes of their internal properties are both equally important in their contribution to cooling our planet. Moreover, they found that the total impact from the influence of aerosols on this type of cloud is almost double that estimated in the latest report of the United Nations Intergovernmental Panel on Climate Change. These finding could lead to an increase in the observed global warming as China begins to clean-up its air pollution:
Yi-Chun Chen, Matthew W. Christensen, Graeme L. Stephens & John H. Seinfeld, (2014), "Satellite-based estimate of global aerosol–cloud radiative forcing by marine warm clouds", Nature Geoscience, doi:10.1038/ngeo2214
http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2214.html15. The linked reference (with a free access pdf) provides evidence that the main source of uncertainty for Arctic climate variability, and its predictability, is the North Pacific. As we know that the North Pacific is projected to warm-up over the next 25 years in order to synchronize with the North Atlantic, it seems likely that we can expect the Arctic to warm rapidly as the North Pacific warms:
Dmitry V. Sein, Nikolay V. Koldunov, Joaquim G. Pinto, William Cabos, (2014), "Sensitivity of simulated regional Arctic climate to the choice of coupled model domain", Tellus A, 66, 23966,
http://dx.doi.org/10.3402/tellusa.v66.23966http://www.tellusa.net/index.php/tellusa/article/view/2396616. The linked 2013 article focuses on changes in the Arctic Ocean, and indicates that changes in the plankton there could result in a positive feedback (that will likely become more important with time) associated both with lower dimethyl sulphide production and lower CO2 absorption:
http://www.egu.eu/news/76/tiny-plankton-could-have-big-impact-on-climate/17. The reference cited below indicates that atmospheric hydroxyl-radical concentrations are about the same in the Northern and Southern Hemispheres. This is bad news as it implies that methane emissions in the Northern Hemisphere are likely higher than researchers have previously assumed (as it was expected that the Northern Hemisphere would have more hydroxyl-radicals than the Southern Hemisphere, and it appears likely that greenhouse gases such as methane are consuming part of store of atmospheric hydroxyl-radicals in the Northern Hemisphere).
P. K. Patra, M.C. Krol, S. A. Montzka, T. Arnold, E. L. Atlas, B.R. Lintner, B.B. Stephens, B. Xiang, J. W. Elkins, P. J. Fraser, A. Ghosh, E. J. Hintsa, D. F. Hurst, K. Ishijima, P. B. Krummel, B.R. Miller, K. Miyazaki, F.L. Moore, J. Mühle, S. O’Doherty, R.G. Prinn, L.P. Steele, M. Takigawa, . J. Wang, R.F. Weiss, S.C. Wofsy, and D. Young, (2014), "Observational evidence for interhemispheric hydroxyl-radical parity", Nature, doi:10.1038/nature13721
http://www2.ucar.edu/atmosnews/just-published/12346/wheres-atmospheres-self-cleaning-power