than the extent of the ice is its volume. I'm not for a moment suggesting that the information in your link is wrong, but it refers to the area covered by ice, rather than the total volume.
Sea levels have been rising for quite a long time, but very slowly - around 1 to 1.5mm a year on average over the last 100 years. In New York, for example, tide gauge measurements show sea levels are currently rising by 2.73 mm a year, and nobody knows whether that will continue at the present rate,or increase. The rise in levels isn't necessarily wholly attributable to melting polar ice; as temperatures rise the oceans are subject to thermal expansion - the volume of the sea water becomes greater as it warms.
Thermal expansion isn't the only answer however. Between 1880 and 1980 world sea levels rose by between 100 and 150mm, and thermal expansion is estimated to account for no more than 20 to 50mm of that. The rest must have come from somewhere, and the only source that could supply that amount of water is ice - melting glaciers and melt water from the polar ice caps. We are talking about huge volumes of water here; it's been estimated (by the US geological survey) that the Greenland ice cap alone contains enough water to keep the Mississippi river flowing at full bore for over 4700 years.
Estimates of the volume of ice in Antarcta vary between 6 and 7 million cubic miles (it has an average thickness of 7000 feet), and if that little lot melted sea levels would rise by about 200 feet all over the planet.
Who knows what's really going on? The answer of course is nobody. All we can do is observe and record what happens, and what's happening at the moment is that temperatures are rising - of thet there's no doubt. Over the 100 years ending in 2005 global air temperatures rose by an average of around 1.3 degrees F, and most scientific bodies are in broad agreement that since 1950 most of the increase is attributable to the so-called greenhouse gas effect.
Land temperatures rise faster than oceans because the seas can lose heat faster by radiation. That accounts for the fact that the Northern hemisphere is warming faster than the Southern - it has a greater land area.
Our planet has been through many warming and cooling cycles in the past, and it may be that our present situation is the result of one of these blips, probably made worse by our activities. When it will change is anyone's guess, but change it will, and let's hope our ancestors are around to witness it.