With its melting glaciers, thawing permafrost and floating sea ice that gets tougher to see from its northern shores each summer, Alaska is the poster state for global warming. Things are changing here, no doubt about it. But it’s not the first time.

If you were to hike across the North Slope 75 million years ago, you would think you were in a Louisiana bayou, with the smell of moist greenery in the air, ferns and evergreens instead of tundra, and the baby Brooks Range nudging upward on the southern horizon.

Back then, your main concern would have been avoiding Albertosaurus, the Alaska version of T-rex, who preyed on the seven other types of dinosaurs living in northernmost Alaska. Albertosaurus and those other cold-blooded reptiles survived in a place that has changed so much that the only current amphibians in northern Alaska — wood frogs — don’t dare hop there today.

The sea ice on top of the world wasn’t even there when the dinosaurs were stomping around. The water on top of the world was then thick with delicate azolla ferns, which now grow in rice paddies in Vietnam.

Alaska glaciers suffered long before the invention of the internal combustion engine. If you sailed past the entrance to Glacier Bay with George Vancouver in the late 1700s, you would have seen a wall of ice where the bay is now. A chunk of ice 1 mile high and 50 miles long has disappeared in few hundred years since then.

That’s impressive, but scientists have also found that Glacier Bay was a bay at least four times in the 10,000 years before Vancouver sailed by. Their best guess is that Glacier Bay has filled and emptied with ice over the centuries because the sun’s strength isn’t constant — sometimes it has more punch than other times, and ice recovers when the sun is weaker.

During a major global warming event from about 18 million to 14 million years ago, basswood trees grew in Fairbanks, hickories in Eagle, elms in Tok. While boating the upper Porcupine River in 1990, a group of scientists pulled over when they saw a stump protruding from the wall of the Porcupine River canyon. It was a sequoia tree, engulfed by lava many moons ago. The farthest-north sequoia alive today lives in Oregon.

[‘The math checks out’: Anchorage-raised doctoral candidate presents a new explanation for a solar mystery]

Today’s changes are also big ones. Recent melting of glaciers is happening at twice the rate at which their ice disappeared 50 years ago. Wedges of ice beneath the soil that have remained solid for thousands of years are thawing. The loss of summer sea ice on top of the world continues as scientists predicted when they first noticed it.

Alaska’s dinosaurs didn’t want change. But it came, and they left their bones in the banks of the Colville River and tracks plastered in rocks in Denali Park as evidence of their temporary dominance. Their reign, by the way, was millions of years longer than our current streak as Earth’s top dogs.

Though we are shoving climate change along with our injudicious burning of oil, gas and coal, we shouldn’t flatter ourselves into thinking we’re the only agent capable of changing the air temperature. More powerful forces are the relative strength of the sun, giant volcanic eruptions, the wobble of the Earth on its axis, and the natural seesawing of large-scale weather patterns that have affected Alaska and the rest of the planet forever.

When you take a hard look at Alaska’s past, it seems that climate stability would be stranger than climate change. Just ask the lions and the camels and the saber-toothed cats that used to roam the plains of Alaska.

[Mastodons vanished from the Arctic thousands of years earlier than researchers had thought]