What is the effect of climate change on the polar ice caps and how is it impacting global sea levels?
Climate change is causing polar ice caps to melt and global sea levels to rise.  Both phenomena have (at least) two different mechanisms of action.  

First, polar ice caps are melting because the world as a whole is just a tiny bit warmer. Second, even more polar ice is melting because the greenhouse effect causes temperatures to equalize more worldwide - which means that the poles get more warming than the rest of the world.  The second effect has caused more temperature change and melting than the first.

Sea levels are rising because of the water volume of melted ice.  But ice that's already floating doesn't change the water level when it melts, so sea level rise from meltwater only happens with ice that had been on land prior to melting.  The main driver of rising sea levels has been that the oceans of the world are one to one and a half degrees (Celsius) warmer than they were previously and water expands as it warms taking up more volume.