The ice that melts in Antarctica and in Greenland as a result of global warming will redistribute into the oceans of the world.  This will involve redistribution of many gigatonnes of mass from the polar regions (close to the earth's axis) to the average latitude of the earth's oceans (further from the earth's axis). This means that to conserve angular momentum the earth should reduce its spin rate.  Has this occurred and if so what is the magnitude of the effect; A - Now - and B - when all the polar ice has melted?

We all know (in the Northern Hemisphere) the days get shorter as we approach the end of December.  The days get longer as we approach June.  But why don't the days get shorter and longer at a uniform rate? 

Example: In September the day length varies by nearly 4 minutes a day. But in December the rate of change is only 1 to 2 minutes.  Around 20th December the change is only about 10 seconds.  Why is this?

If you want to 'play' with this, take a look at: http://www.timeanddate.com/worldclock/astronomy.html?n=136&month=12&year=2010&obj=sun&afl=-11&day=1