Good to mention that the same journal published another set of Antarctic sea level rise projections one year before (2015) that are far less dire (Potential sea-level rise from Antarctic ice-sheet instability constrained by observations). This, and much more background on this Grist article, is highlighted in a great Guardian article written by Tamsin Edwards: How soon will the 'ice apocalypse' come?

This is a statement that difficult to justify without a reference to scientific evidence. The current knowledge of time scales involved with rapid ice sheet loss is poor (i.e. solely based on ice sheet models that are crude) - that's the primary reason why the "How Much How Fast" US-UK program was established.

This is strongly supported by the DeConto and Pollard 2016 Nature paper, which showed that Antarctic contribution to committed sea level rise can be limited to ~20 cm in a strong climate mitigation scenario (RCP2.6).

Regarding ice shelf stability, it is important to acknowledge (which Eric didn't do here) there are different processes at work on the Antarctic Peninsula (where the Larsen ice shelves reside(d)) than on the Amundsen coast (Pine Island and Thwaites ice shelves). The Larsen A and B ice shelves were very thin, and have disintegrated from percolating surface meltwater (hydrofracturing) creating vertical cracks in the ice shelf. Larsen C is thicker and larger, but is also characterised by a relatively warm climate (many melt episodes in summer) and low snowfall (which makes it vulnerable to atmospheric warming). The ice shelves that buttress the Pine Island and Thwaites glaciers are much thicker, annual snowfall rates are very large, and surface melt rates are substantially lower than on the (former) Larsen ice shelves (3-5 times lower). Therefore, it is highly unlikely that surface-based ice shelf instability will occur within the next few decades - instead, these ice shelves would likely thin though contact with warmer ocean waters.

This is the prime motive of understanding Antarctic ice sheet dynamics, especially since the far-field location gives Antarctica relatively more weight to sea level rise along many northern hemisphere cities than Greenland.

This is true, but referring to West Antarctic ice sheet would be more precise.

This is not per se completely incorrect, but the author does not tell us the whole story. The author refers to the growing of the ice sheet volume through snowfall throughout winter. The snow accumulated on Greenland in past winter (September-April) has indeed been remarkably high:

However, this does not imply that the volume of the ice sheet is increasing, because (1) the ice sheet also loses ice through discharging icebergs; it is the difference between snowfall-driven growth and solid ice discharge that determines if the ice sheet gains or loses volume.

(2) the snow that accumulated during the winter will (at least partly) melt over the summer. That's why we analyse changes to the ice sheet volume/mass on (at least) annual time scales. Only after the summer we will know how much of the accumulated snow has (not) been melted. During the past years, the amount of melting has been record-high, and much of snow that accumulated over the winter melted and ran off into the ocean. Concurrently, ice discharge continued, so the Greenland ice sheet LOST considerable volume. We will know in September how much the ice sheet has changed volume this year.

Two additional remarks:

(a) The word 'faster' should not have been used here. We are not talking about the rate of speed, but rather about the total change in volume. Also, it is easier to talk about 'mass changes' than 'volume changes' since the former is not sensitive to the density of the medium we are talking about (snow has a lower density than ice!).

(b) the enhanced snowfall, ironically, is most probably also a signal of the strongly warming Arctic: as the atmosphere warms, it contains more moisture, and generates more precipitation. Also, record-low fall and winter sea ice extent led to large streaks of open water that might have contributed to additional moisture loading of the air.

This is a largely false statement. The correct part is the East Antarctic ice sheet is close to mass balance (e.g. Shepherd et al., 2012; Gardner et al., 2017 (just published today)) and that the recent changes in Antarctic sea ice cover are explained by natural variability (Turner et al., 2016; Meehl et al, 2016).

The statement is definitely false for Arctic sea ice, which is decreasing dramatically since the 1990's as a response to human greenhouse gas emissions. In fact, there is a direct and linear relation between CO2 emitted and sea ice decline: each metric ton CO2 emitted leads to a 3 m2 loss of Arctic sea ice (Notz and Stroeve, 2016). The current loss of sea ice falls outside of natural variability and has been unprecedented in at least the last 1,450 years (Kinnard et al., 2011).

West Antarctic mass loss is rapidly increasing since the 1990's (e.g. Gardner et al., 2017). Glacial retreat in the Amundsen Sea region, the main driver of this mass loss, appears to have started already in the earlier 20th century (Smith et al., 2016). The rate of retreat is rapid and widespread (Rignot et al., 2014), with no mechanism for future stabilisation (Joughin et al., 2014).

Current ice sheet mass loss contributes significantly (almost 40%, Rietbroek et al., 2016) to observed 21st century sea level rise. Until 2016, Arctic sea ice loss has dominated over slight Antarctic sea ice gain. In 2016 and 2017, Antarctic sea ice has been in decline as well, and reasons for this are currently under study.

References

Gardner, A.S., Moholdt, G., Scambos, T., Fahnstock, M., Ligtenberg, S., van den Broeke, M., Nilsson, J., 2017. Increased West Antarctic ice discharge and East Antarctic stability over the last seven years. Cryosph. Discuss. 1–39.

Joughin, I., Smith, B.E., Medley, B., 2014. Marine ice sheet collapse potentially under way for the Thwaites Glacier Basin, West Antarctica. Science. 344, 735–738.

Kinnard, C., Zdanowicz, C.M., Fisher, D.A., Isaksson, E., de Vernal, A., Thompson, L.G., 2011. Reconstructed changes in Arctic sea ice over the past 1,450 years. Nature 479, 509–512.

Meehl, G.A., Arblaster, J.M., Bitz, C.M., Chung, C.T.Y., Teng, H., 2016. Antarctic sea-ice expansion between 2000 and 2014 driven by tropical Pacific decadal climate variability. Nat. Geosci. 9, 590–595.

Mouginot, J., Rignot, E., Scheuchl, B., 2014. Sustained increase in ice discharge from the Amundsen Sea Embayment, West Antarctica, from 1973 to 2013. Geophys. Res. Lett. 41, 1576–1584.

Notz, D., Stroeve, J., 2016. Observed Arctic sea-ice loss directly follows anthropogenic CO 2 emission. Science. 1–9.

Rietbroek, R., Brunnabend, S.-E., Kusche, J., Schröter, J., Dahle, C., 2016. Revisiting the contemporary sea-level budget on global and regional scales. Proc. Natl. Acad. Sci. U. S. A. 113, 1504–1509.

Rignot, E., Mouginot, J., Morlighem, M., Seroussi, H., Scheuchl, B., 2014. Widespread, rapid grounding line retreat of Pine Island, Thwaites, Smith, and Kohler glaciers, West Antarctica, from 1992 to 2011. Geophys. Res. Lett. 41, 3502–3509.

Shepherd, A., Ivins, E.R., A, G., Barletta, V.R., Bentley, M.J., Bettadpur, S., Briggs, K.H., Bromwich, D.H., Forsberg, R., Galin, N., Horwath, M., Jacobs, S., Joughin, I., King, M.A., Lenaerts, J.T.M., Li, J., Ligtenberg, S.R.M., Luckman, A., Luthcke, S.B., McMillan, M., Meister, R., Milne, G., Mouginot, J., Muir, A., Nicolas, J.P., Paden, J., Payne, A.J., Pritchard, H., Rignot, E., Rott, H., Sörensen, L.S., Scambos, T.A., Scheuchl, B., Schrama, E.J.O., Smith, B., Sundal, A. V, van Angelen, J.H., van de Berg, W.J., van den Broeke, M.R., Vaughan, D.G., Velicogna, I., Wahr, J., Whitehouse, P.L., Wingham, D.J., Yi, D., Young, D., Zwally, H.J., 2012. A Reconciled Estimate of Ice-Sheet Mass Balance. Science. 338, 1183–1189.

Smith, J.A., Andersen, T.J., Shortt, M., Gaffney, A.M., Truffer, M., Stanton, T.P., Bindschadler, R., Dutrieux, P., Jenkins, A., Hillenbrand, C.-D., Ehrmann, W., Corr, H.F.J., Farley, N., Crowhurst, S., Vaughan, D.G., 2017. Sub-ice-shelf sediments record history of twentieth-century retreat of Pine Island Glacier. Nature 541, 77–80.

Turner, J., Hosking, J.S., Marshall, G.J., Phillips, T., Bracegirdle, T.J., 2016. Antarctic sea ice increase consistent with intrinsic variability of the Amundsen Sea Low. Clim. Dyn. 46, 2391–2402.

I would appreciate a caption and legend in the figure below.

This is slightly confusing, since it can refer to either sea ice gain or land ice gain (which were both mentioned by skeptics). The sea ice gain since 2000 has been attributed to natural, decadal variability in the tropical Pacific. Land ice gain is a false claim, and mostly refers to slight thickening of the East Antarctic interior, which is more than compensated by dynamic ice loss in West Antarctica.

That is correct, see figure below: . There was an event in the beginning of July where ~50% of the ice sheet experienced melt. This is clearly outside of the expected natural variability, but does not necessarily project the overall Greenland summer (since such melt events are extremely episodic). Overall, Greenland experienced a warm summer, with slightly more surface runoff than average and overall average amounts of snowfall (source)

The figures below are illustrative but not at all discussed in the text.

This is vague. Better would be 'The report' or 'The authors of the report'

Like posted above, this does not necessarily reflect its contribution to sea level.

an atmospheric

and ice sheets.

Not sure if this entirely appropriate. I would say that it increases 'global mean temperature'. An El Nino does not necessarily imply warming everywhere on Earth. Also, especially pronounced are the warm conditions in the Arctic, which are not explicitly mentioned here, but do not relate to the strong El Niño.

This statement - again- cannot be validated. Who are the 'many scientists'? It is well known that the scientific consensus (with the climate science community) is that the globe is warming and will warm up further in the near future. Longer term warming is dependent on human interventions in mitigating carbon dioxide emissions (IPCC AR5, see www.ipcc.ch). According to IPCC AR5, potential negative feedbacks, such as cooling in the North Atlantic region (Eastern US, Western Europe) due to slowing down the Atlantic meridional circulation, are highly unlikely to occur in the 21st century.

The words from Barack Obama reflect the conclusions from IPCC AR5, which in turn reflects the consensus of the scientific community. Read the Summary for Policymakers for the most synthesized summary.

This part clearly picks an “expert" without academic credential on the issue. Roger Cohen is just one scientist, whereas the scientific consensus (peer-reviewed literature, IPCC) is clear that the warming trend is not over yet, despite a more modest increase in global temperature after the major El Niño of 1997-1998. The 'warming hiatus', attributed to interdecadal variability or enhanced ocean heat storage, has recently been recalled by NOAA See news article in The Guardian. 2014 was the hottest year on record (since 1880), and 2015 will most probably beat that record.

This statement is very hard to validate, since any citation is missing. I did find a paper (VanLooy et al., 2006) describing thickness change of several glaciers on the Kenai peninsula from 1950 to the mid-1990's. Almost all glaciers showed thinning before the 1990's, but that thinning accelerated in the 1990's with a mean factor of 1.5, and even 2.5 for Exit Glacier. Because of the lack of Digital Elevation Maps between the 1950's and 1990's, it is unknown if the glacier thinning occurred monotonically within this period, or whether it was focussed on the latter part of the time series.

VanLooy, J., R. Forster, and A. Ford (2006): Accelerating thinning of Kenai Peninsula glaciers, Alaska. Geophys. Res. Lett., 33, 21, doi:10.1029/2006GL028060