A4R,
That is a great summary article, and the following article (and attached image) by Steig et al 2013 provides further elaborations about our risks:
Recent climate and ice-sheet changes in West Antarctica compared with the past 2,000 years
by: Eric J. Steig, et al., Nature Geoscience; 6, 372–375; (2013); doi:10.1038/ngeo1778
Abstract
"Changes in atmospheric circulation over the past five decades have enhanced the wind-driven inflow of warm ocean water onto the Antarctic continental shelf, where it melts ice shelves from below. Atmospheric circulation changes have also caused rapid warming4 over the West Antarctic Ice Sheet, and contributed to declining sea-ice cover in the adjacent Amundsen–Bellingshausen seas. It is unknown whether these changes are part of a longer-term trend. Here, we use water-isotope (δ18O) data from an array of ice-core records to place recent West Antarctic climate changes in the context of the past two millennia. We find that the δ18O of West Antarctic precipitation has increased significantly in the past 50 years, in parallel with the trend in temperature, and was probably more elevated during the 1990s than at any other time during the past 200 years. However, δ18O anomalies comparable to those of recent decades occur about 1% of the time over the past 2,000 years. General circulation model simulations suggest that recent trends in δ18O and climate in West Antarctica cannot be distinguished from decadal variability that originates in the tropics. We conclude that the uncertain trajectory of tropical climate variability represents a significant source of uncertainty in projections of West Antarctic climate and ice-sheet change."
The attached image focuses on recent WAIS trends are measured by precipitation δ18O; and based on such data I caution that due to the non-linearity of ice mass loss from the WAIS, in the future when the peaks of the natural variability are superimposed on the anthropogenic trend; we can expect a strong increase in ice mass loss from the WAIS in the coming decade (or two) that may be strong enough to push the WAIS ice mass loss past a tipping point.
Caption for the attached figure:
"Fig. S8. Results of a 1-tailed Student’s t-test comparing the decadal-mean for each of the ten members of the ensemble of simulated δ18O in West Antarctic precipitation from the AMIP/coupled experiment for each decade beginning starting in 1865, compared with the 1990’s. As for the observations, the 1990s are distinct from the preceding three decades at moderately high confidence p~0.1, but distinct from the 1940’s and earlier decades only at low confidence. Note that because the quality of the tropical SST data diminishes significantly prior to the latter half of the 20th century, the lack of correspondence between Figs. S4 and Fig. S8 for the late 19th/early 20th century cannot be interpreted as model/data disagreement."