you can also have a situation with a lot of thick (old) ice over a small area, versus a lot of ice coverage of very thin (new) ice. Thin ice is quick to form and quick to melt, and easily broken up and moved around by wind and wave action. Unfortunately, old and new ice look exactly the same in satellite imagery.

The surface ice area is easy to measure by satellite, but the thick, old or MYI (multi-year ice) has to be modeled from multiple data sources so the measurements aren't quite as reliable. How the ice is divided into different types throughout the year also tells us something about the processes involved. And sometimes ponds of melt water ON the ice mislead the sensors, as do thick layers of porous, fluffy snow on top of pack ice.

The point is that the people who study this have lots of tools and lots of different ways to study it. They've learned a great deal and they really care, they really want to understand this because not only is it interesting science, but it is so important to all of us. You can see why we get so impatient with the denialists who dismiss it all as just another liberal conspiracy to raise taxes and regulate business. Taxes and regulation seem to be the only thing these people care about.

Check out the National Snow and Ice Data Center, JAXA (the Japanese Space Agency) and the Neven ice blog, which I often cite here and they will point you to other agencies and institutes and data sites that study this problem. This is real, this is important, it really matters. They don't always agree, which is what you'd expect in a developing field at the frontiers of knowledge. The scientists DO agree that something BIG is happening to the Earth's climate but they are full of disagreement and debate as to just how it will play out. This is exactly as it should be in science. But at least they are trying to get it right, not confuse the issue or change the subject altogether

You have to excuse me if I get a bit short-tempered with those who are doing every thing they can to discredit this work for purely political and economic reasons. They are simply unforgivable. They are no better than slavers, pimps, war criminals, drug lords, human traffikers, or arms merchants.