And Alaska was once perpetually green and tropical. Who's to say (Al Gore, call your orifice) that that's not normal and it shouldn't be that way again?
Good chance that Alaska was NOT located where it is now when it was green. Maybe it will be greener than it is now. Who knows.
I know that about 10,000 years ago, give or take a week, that a Woolly Mammoth got trapped in mud in Siberia, that was NOT permafrost as it is now and then became frozen in time and place.
Nature does as nature wants.