What they are omitting is that they know perfectly well when and why the Antarctic ice sheet formed--what happened was that Antarctica and South America separated and the South Circumpolar Current started to flow--when that happened the cold air was trapped and Antarctica froze--it has been frozen ever sense--and will remain that way as long as the South Circumpolar Current flows--tens of millions of years, and no end in sight. It has been quite a bit warmer than today and it hasn't melted, nor will it.