by Judith Curry
A few things that caught my eye this past week.
Paper of the week:
Decreasing cloud cover drives recent mass loss on the Greenland ice sheet
Abstract. The Greenland Ice Sheet (GrIS) has been losing mass at an accelerating rate since the mid-1990s. This has been due to both increased ice discharge into the ocean and melting at the surface, with the latter being the dominant contribution. This change in state has been attributed to rising temperatures and a decrease in surface albedo. We show, using satellite data and climate model output, that the abrupt reduction in surface mass balance since about 1995 can be attributed largely to a coincident trend of decreasing summer cloud cover enhancing the melt-albedo feedback. Satellite observations show that, from 1995 to 2009, summer cloud cover decreased by 0.9 ± 0.3% per year. Model output indicates that the GrIS summer melt increases by 27 ± 13 gigatons (Gt) per percent reduction in summer cloud cover, principally because of the impact of increased shortwave radiation over the low albedo ablation zone. The observed reduction in cloud cover is strongly correlated with a state shift in the North Atlantic Oscillation promoting anticyclonic conditions in summer and suggests that the enhanced surface mass loss from the GrIS is driven by synoptic-scale changes in Arctic-wide atmospheric circulation.
We put forward the idea in our new piece that solar geoengineering would more effectively reduce surface melt of glaciers than the same reduction in RF achieved by emissions cuts
Fredericke Otto: When we started out doing event attribution we thought heatwaves would be the easy stuff. Turns out at least in some parts of the world disentangling local drivers and climate change is very challenging [link]
Climate variability in the subarctic area for the last 2 millennia [link] …
Using emerging constraints, Brown & @KenCaldeira (2017) estimates ECS of 2.8-4.5K (66%) while @coxypm et al (2018) estimate 2.2-3.4K (66%). Are these ranges too low as structural uncertainties not sufficiently considered? [link] …
James Annan on the Cox et al. climate sensitivity paper [link]
Reductions in European sulfur emissions in the last decades have probably caused the Arctic region to warm by 0.5°C! [link] …
Multidecadal Variability in Global Surface Temperatures Related to the Atlantic Meridional Overturning Circulation [link]
Biomass-based negative emissions difficult to reconcile with planetary boundaries [link]
There’s growing evidence for geothermal activity all across Greenland [link]
.@AlanRobock & colleagues published what appears to be a solid paper on the possble impacts of the sudden termination of solar #geoengineering, concluding it “would significantly increase the threats to biodiversity from climate change” [link] …
Gulf Stream Excursions and Sectional Detachments Generate the Decadal Pulses in the Atlantic Multidecadal Oscillation [link]
A very good article on the recent California fires [link]
Towards predicting changes in the land monsoon rainfall a decade in advance [link]
Some Viking settlements in Greenland are still burried under ice since the ending of the MWP. If using Greenland as a gauge sea levels had to be same or higher then now. Also lots of MWP artifacts appearing a ice edges in N Hem in last 8 or so years. [link]
Interacting Antarctic glaciers may cause faster melt and sea level contributions http://phy.so/435916806
Linear and nonlinear hydrological cycle responses to increasing sea surface temperature [link]
A study out last week found little evidence to support the ‘arctic methane bomb’ (clathrate-style) hypothesis, which is good news! Still a lot to learn about this, though. [link]
Sources of uncertainty in hydrological climate impact assessment: a cross-scale study [link]
Impacts and Policy
Reckoning with climate change will demand ugly tradeoffs from environmentalists [link]
Fighting climate change? We’re not even landing a punch [link]
“The ultimate fear with geoengineering is that we’re trying to alter a system that’s much too complex for us to truly predict”- [link] …
Shifting from beef to poultry has a bigger absolute environmental impact than shifting from poultry to plants. [link]
Does replacing coal with wood lower #CO2 emissions? Probably not. New ERL paper by John Sterman et al, providing dynamic lifecycle analysis of wood #bioenergy [link] …
About Science and Scientists
Sarah Myhre in Newseeek: Science should be a feminist institution. [link]