Here he is:
"The column contained many factual assertions but only one has been challenged."
Apparently the Post doesn't care about lies of omission, where approximately one million blogs have pointed out Will's reference to a prediction of an oncoming ice age omitted that the prediction was for the next "several thousand years."
Will claims he's right about his sea ice levels. He relies on a correction to the data that came out after his column was published (so it wasn't the basis of the claim), and that correction reduces but does not eliminate his error.
I still say asparagus pee is the only solution.