This animation in Google Earth shows satellite data of Arctic sea ice concentration from May 25 to August 21, 2008. Note how the decline rate speeds up during August, with strong losses north of Siberia. For more details, visit http://nsidc.org/arcticseaicenews/20080825#figure3.
@tardgo If the artic becomes ice free in summer, there would be little change in climate during winter, as evaporation would not change due to very low tempretures anyway. There would be a change during summer, but a smaller one than expected, the Artic has a very low troposphere, and is filled mainly with descending air, even if convection increased, there would be little chance of transporting that air anywhere, so the artic would still be dry.
QuantumOverlord 9 months ago