Scientists are increasingly concluding that changes in low level cloud cover, not CO2, are what govern the surface radiation budget in the polar regions, driving and determining the retreat of the ice sheets.
Image Source: https://www.nature.com/articles/nclimate3363
It is considered “established science” that “the greenhouse effect of clouds may be larger than that resulting from a hundredfold increase of the C02 concentration of the atmosphere” (Ramanathan et al., 1989, 1,647 citations to date).
Indeed, satellite observations indicate that the Earth’s “radiation budget changes are caused by changes in tropical mean cloudiness” (Wielicki et al., 2002), not CO2 concentration changes.
Consequently, scientists have increasingly concluded that the driving mechanism that has governed and determined the melt of the polar ice sheets during recent decades has been the natural decadal-scale changes in cloud cover.
Decreasing cloud cover drives the recent
mass loss on the Greenland Ice Sheet
“The Greenland Ice Sheet (GrIS) has been losing mass at an accelerating rate since the mid-1990s. … 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. … Th[e] strong correlation between summertime NAO index and the MAR-based cloud cover could be used to forecast whether the observed reduction in cloud cover during summer, and the associated increase in GrIS melt, is likely to continue.”