In my last post I pointed out that focusing on the consideration that it could conceivably take as long as 200-yrs for the ASE glaciers to collapse, rather than on the fact that this period to ASE collapse will almost certainly be shorter (and possibly much shorter), is like putting "Lipstick on a PIG (Pine Island Glacier)". Indeed, the past 40-yr period considered by the NASA was dominated by many temporary climate change "masking factors", that cannot be counted on to continue for an extended period of time as partially pointed out by Michael Mann in his April 2014 SciAm article: "False Hope: The rate of global temperature rise may have hit a plateau, but a climate crisis still looms in the near future":
Mann, M.E., False Hope: The rate of global temperature rise may have hit a plateau, but a climate crisis still looms in the near future, Scientific American, p. 78-81, April 2014.
Further to the SciAm article Michael Mann points out that a significant portion of the "Faux Pause" from 1999 to 2014 was associated with a cooling phase of the NAO, which will reverse soon enough (see reference below):
Mann, M.E., Steinman, B.A., Miller, S.K., On Forced Temperature Changes, Internal Variability and the AMO, Geophys. Res. Lett. (“Frontier” article), doi:10.1002/2014GL059233; May1, 2014
http://www.meteo.psu.edu/holocene/public_html/Mann/articles/articles/MannEtAlGRLOnline14.pdfAbstract: "We estimate the low-frequency internal variability of Northern Hemisphere (NH) mean temperature using observed temperature variations, which include both forced and internal variability components, and several alternative model simulations of the (natural + anthropogenic) forced component alone. We then generate an ensemble of alternative historical temperature histories based on the statistics of the estimated internal variability. Using this ensemble, we show, first, that recent NH mean temperatures fall within the range of expected multidecadal variability. Using the synthetic temperature histories, we also show that certain procedures used in past studies to estimate internal variability, and in particular, an internal multidecadal oscillation termed the “Atlantic Multidecadal Oscillation” or “AMO”, fail to isolate the true internal variability when it is a priori known. Such procedures yield an AMO signal with an inflated amplitude and biased phase, attributing some of the recent NH mean temperature rise to the AMO. The true AMO signal, instead, appears likely to have been in a cooling phase in recent decades, offsetting some of the anthropogenic warming. Claims of multidecadal “stadium wave” patterns of variation across multiple climate indices are also shown to likely be an artifact of this flawed procedure for isolating putative climate oscillations."
Furthermore, while the "Forcing" thread contains many references that cite mechanisms that indicate that climate change forcing is probably higher than that used in most GCMs/RCMs that project ice mass loss from WAIS; the following is a partial list of factors that are currently masking the full consequences of many of these climate change forcings:
(1) Aerosols (eg sulfates from burning coal) have masked the build-up of GHGs which will be felt when the air pollution is reduced (as China has pledged to do).
(2) Volcanic eruptions have masked many of the impacts of the last negative phase of the IPO/PDO (El Nino hiatus). For example: in 1991 Mt Pinatubo erupted in the Philippines; and in 1963 Mt. Agung erupted in Bali; however, such events are relatively rare and cannot be counted on to reoccur in the near future.
(3) The thinning of Arctic sea ice is delaying consequences of the coming albedo change, which could come as soon as 2017 +/- 2 yrs.
(4) Thermal inertia of the permafrost is delaying the coming CO₂ & methane emissions; which is starting to accelerate already.
(5) Thermal inertia of the ocean delays most changes in mean global temperature by up to 50-years; meaning that we cannot stop the acceleration of the loss of the ASE glaciers and the WAIS.
(6) We were slowly entering an ice age when AGW began; which temporarily slowed the rate of warming.
(7) Vegetation can accommodate a certain amount of climate change before suffering from stress, and while there has been a recent temporary increase in vegetation worldwide, this trend is likely to stop within the next could of decades, and as indicated by the following two references, vegetation has been emitting aerosol precursors that has been temporarily slowing the rate of AGW, but when the vegetation cannot keep up with the rate of AGW (or more likely declines due to AGW induced stress), we can expect AGW to further accelerate:
In a study by Salo, et.al, 2011, the authors argue that climate sensitivity could be ‘greater than previously believed’ because in the initial phases of the current CO2-induced warming plant life has emitted larger amounts of precursor gases that lead to the formation of reflective or blocking secondary organic aerosols (SOA) in the atmosphere, thereby acting as a negative climate feedback, and masking part of the ‘warming’ that’s occurring underneath.
Salo, K., Hallquist, M., Jonsson, A.M., Saathoff, H., Naumann, K.-H., Spindler, C., Tillmann, R., Bohn, B., Rubach, R., Mentel, Th.F., Muller, L., Hoffmann, T., and Donahue, N.M. (2011); "Volatility of secondary organic aerosol during OH radical induced ageing"; Atmos. Chem. Phys., 11, 11055-11067, 2011; doi: 10.5194/acp-11-11055-2011.
Pauli Paasonen et al, (2013), "Warming-induced increase in aerosol number concentration likely to moderate climate change", Nature Geoscience, 6,pp: 438–442 (2013)doi:10.1038/ngeo1800
http://www.nature.com/ngeo/journal/v6/n6/full/ngeo1800.htmlAbstract: "Atmospheric aerosol particles influence the climate system directly by scattering and absorbing solar radiation, and indirectly by acting as cloud condensation nuclei. Apart from black carbon aerosol, aerosols cause a negative radiative forcing at the top of the atmosphere and substantially mitigate the warming caused by greenhouse gases. In the future, tightening of controls on anthropogenic aerosol and precursor vapour emissions to achieve higher air quality may weaken this beneficial effect. Natural aerosols, too, might affect future warming. Here we analyse long-term observations of concentrations and compositions of aerosol particles and their biogenic precursor vapours in continental mid- and high-latitude environments. We use measurements of particle number size distribution together with boundary layer heights derived from reanalysis data to show that the boundary layer burden of cloud condensation nuclei increases exponentially with temperature. Our results confirm a negative feedback mechanism between the continental biosphere, aerosols and climate: aerosol cooling effects are strengthened by rising biogenic organic vapour emissions in response to warming, which in turn enhance condensation on particles and their growth to the size of cloud condensation nuclei. This natural growth mechanism produces roughly 50% of particles at the size of cloud condensation nuclei across Europe. We conclude that biosphere–atmosphere interactions are crucial for aerosol climate effects and can significantly influence the effects of anthropogenic aerosol emission controls, both on climate and air quality."
Robert J. Allen, Joel R. Norris & Mahesh Kovilakam, (2014), "Influence of anthropogenic aerosols and the Pacific Decadal Oscillation on tropical belt width", Nature Geoscience, 7, 270–274, doi:10.1038/ngeo2091
http://www.nature.com/ngeo/journal/v7/n4/full/ngeo2091.htmlAbstract: "The tropical belt has widened by several degrees latitude since 1979, as evidenced by shifts in atmospheric circulation and climate zones. Global climate models also simulate tropical belt widening, but less so than observed. Reasons for this discrepancy and the mechanisms driving the expansion are uncertain. Here we analyse multidecadal variability in tropical belt width since 1950 using the Coupled Model Intercomparison Project Phase 5 climate model runs and find that simulated rates of tropical expansion over the past 30 years—particularly in the Northern Hemisphere—are in better agreement with observations than previous models. We find that models driven by observed sea surface temperatures over this interval yield the largest rate of tropical expansion. We link the tropical expansion in the Northern Hemisphere to the leading pattern of sea surface temperature variability in the North Pacific, the Pacific Decadal Oscillation. We also find, both from models and observations, that the tropical belt contracted in the Northern Hemisphere from 1950 to 1979, coincident with the reversal of the Pacific Decadal Oscillation trend. In both time periods, anthropogenic aerosols act to modify the Pacific Decadal Oscillation and therefore contribute to the width of the tropical belt. We conclude that tropical expansion and contraction are influenced by multidecadal sea surface temperature variability associated with both the Pacific Decadal Oscillation and anthropogenic aerosols."
To repeat, as currently estimates of "climate sensitivity" do not include this vegetation aerosol precursor negative feedback; in order for Global Circulation Models, GCM's including this negative feedback to match historical records they will need to utilize higher effective "climate sensitivity" values; which should resulting in higher projections of global temperature increase, if plant growth/activity does not keep path with the rate of future greenhouse gas, GHC, emissions.
