Just because Alaska was once a tropical sea is meaningless, because nobody denies that the climate can change. Human civilization has flourished in a narrow window where agriculture is possible. Proliferating the carbon in our fuels and bringing our planet back to Pennsylvanian period atmospheric levels would be devastating for most species on this planet. The planet cooled during the Pennsylvanian because of glaciation triggered by the drifting continent of Gondwana. And the carbon that built up in the Carboniferous did so over geologic periods, not periods distinguished by a handful of human generations.
The oceans are particularly sensitive to quick changes like we're imposing now. The fossil record, the geologic record, and our climate record all point towards trouble. It's like walking into a booby trap with the writing on the walls.
And for what it's worth, climate change is a more accurate term, and it's the term you find in the scientific literature. Global warming was used early on when it was hypothesized that we should experience global warming due to the greenhouse gases our industry was creating, and by the late 1990's, it was already clear that the globe was warming. In the early 2000's, attribution to human activities was made possible by our records. The academics refer to climate change in their investigations because global warming is only one part of what our activities are producing in the climate system.
