This is an updated version of the regularized global glacier volume estimates from Cogley (2012). I have included 2 new estimates: one by myself (G13) and another from Huss and Farinotti (HF12). These two papers are the first to use the new Randolph Glacier Inventory (they used v2). Less ice in the world means a smaller potential contribution to sea level rise. That is the good news. The bad news is that it also implies thinner glaciers. Thinner glaciers will melt more easily (the rate of glaciated area loss will be quicker).
The IPCC AR5 sea level chapter considered instability of marine-based sectors of the ice sheets to be unlikely (Church et al., 2013). However, post-AR5 modelling indicates that Pine Island Glacier in Antarctica is already engaged in an unstable retreat (Favier et al., 2014), a situation that is projected to extend to neighboring Thwaites glacier (Favier et al., 2014), and even to East Antarctica (Sun et al., 2014). A recent observational study found an observed sustained increase in ice discharge from the Amundsen Sea Embayment, West Antarctica, from 1973 to 2013 (Mouginot et al. 2014). This prompted this reaction from Eric Steig:
I am disappointed in how the sea level rise projection uncertainties are presented in the IPCC AR5. The way the numbers are presented makes people believe 98 cm by 2100 is a worst-case scenario which it clearly isn’t. The AR5 does have caveats which explains why it could be more, but unfortunately this is buried in language that clearly goes over the heads of most people.
It can be quite difficult to interpret what likely exactly means sometimes. For example in the AR5 sea level chapter they report a likely range of 21-33 cm for thermal expansion (RCP8.5 table 13.5). I have taken that to mean that this was the 66% uncertainty interval based on the IPCC uncertainty guideline note (see table 1). However, I just realized that this range was actually calculated as the 5-95% range from CMIP5. From table 1 I would have called that the very likely range. Can anybody explain to me the motivation for calling it the likely range?
We examined the impact of the 5 & 9 most major volcanic eruptions on global sea level. We construct a record of sea level and its uncertainty since 1854. From this we isolate the volcanic signature which surprisingly behaves very differently than models predict. The mechanism that explains the result is: