A History Of Climate Change

By KBJR News 1

August 4, 2010 Updated Aug 4, 2010 at 10:47 AM CST

There is a great deal of talk these days about climate change, but it's hardly a new phenomenon.

The Earth is billions of years old and throughout its history the surface has been constantly evolving.

The Northland has seen some amazing shifts in its history, and some of those changes have had world-altering consequences as Meteorologist George Kessler reports.

One of the biggest challenges in discussing climate change is getting people to think outside human time scales.

For us, a decade is a long time for the Earth, it's an eye-blink.

To get an idea of how amazing those changes can be, we're going to look back a mere 20,000 years.

At that time, the Northland was a frozen wasteland.

Glacier ice, a mile to a mile-and-a-half thick, covered the ground.

It was a featureless plain of ice- no hills, no lakes and no life to speak of but change was coming.

By 13,000 years ago the ice was gone, and a version of Lake Superior had taken shape.

"As the ice of this Marquette phase began to retreat the ponded water between itself and the higher topography around the western end of Lake Superior and so there was a glacial lake dammed up in front of the retreating ice, it was called glacial lake Duluth. And that lake drained through two courses. One initially drained out the portage river to Moose Lake, and Moose Lake into the Kettle River. Later it drained down the Brule River in Wisconsin."

With the glaciers gone, the Northland was now a tundra environment and some exotic creatures began to filter northward.

Woolly Mammoths, Saber Toothed Cats, Giant Sloths and beavers the size of black bears roamed portions of Minnesota and Wisconsin.

Compared to the height of the ice age it was a warm spell, but it wasn't going to last.

About 11,000 years ago the Northern Hemisphere experienced a sudden and extreme cool-down, known as the Younger-Dryas event.

Ice surged back down the Lake Superior basin, wiping out Glacial Lake Duluth.

The glacier stayed for a few centuries, but then the climate abruptly warmed again.

During the post glacial between about 8,000 and 5,000 years ago the climate was significantly warmer here and the main indication for that is the record of vegetation that we get from lake sediment cores for example suggest that the prairie encroached probably around the order of 150 miles from its current border toward the east and north east. So prairie had encroached into north eastern Minnesota. So the climate here would have been similar to say the climate in SW Minnesota today.

Ever since we hit that peak in temperatures five to eight thousand years ago, the climate has been getting slowly cooler.

This graph represents temperatures from the end of the last ice age.

Basically to today and they were derived from ice cores and ocean sediment cores that are able to look back in time and at least track the climate.

So there's a lot of variation in these individual lines.

The black line represents the average. So everybody comes up out of the cold of the last ice age.

Then we hit that peak from five to eight thousand years ago and then you see we've gradually been getting cooler in the intervening time period.

The other thing you need to take away from this graph is how each of these individual lines is going up and down up and down very sharply.

The climate is a cyclic process. In fact it never holds still.

When the first people arrived in North America it was covered with an ice sheet larger than Antarctica, and a land bridge connected our continent to Asia.

In the centuries after their arrival, a whole new world emerged from under the ice- huge lakes formed, drained, and formed again.

Many species became extinct.

Several different environments have come and gone - Lake Superior went from non-existent to 400 feet deeper than it is today.

Our tundra formed, was replaced by northern forest, which in turn gave way to prairie and hardwoods and has now gone back to the northern species.

"Change is inevitable. It's the rate of change that is critical and to what degree we contribute to rates of change that may be so rapid that its difficult to adapt to."

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