They don't know why? I'm no computer expert but I know one thing, faulty information leads to faulty conclusions.
If you include the massive heat energy consumed by ice melting phase change, then the temperatures we are recording are exactly as predicted.
are you saying ice never melted before?
NEVER to this degree.
There was no North Pole navigation route for the last 10,000 years at least, until 2007.
That is absolute, unmitigated bullshit. The fact is that there is more ice in the arctic now than there has been for most of the past 10,000 years.
Here is a gold standard (according to climate science) GISP2 temperature reconstruction derived from ice cores taken above the arctic circle. As you can see, the temperature today is colder than it has been for most of the past 10,000 years.
Here is a graph from the peer reviewed, published Stein, et al showing the arctic ice coverage for the past 10,000 years. As you can see, there are several periods during the past 10,000 years when the arctic may well have been all but ice free. During the period between 7500, and 9500 years ago the arctic was almost certainly ice free during the summer.
Instead of relying on opinion pieces from people with an agenda, you might try looking to the actual literature that is being published. Clearly whoever told you that the north pole has less ice now than it has at any time in the past 10,000 yers didn't have a clue...or perhaps knew, but chose to lie in order to support a narrative. In either case, you are sadly misinformed.