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[AJE]

A Geological Brief History of Ice Ages and Warming

Global warming started long before the "Industrial Revolution" and the invention of the internal combustion engine. Global warming began 18,000 years ago as the earth started warming it's way out of the Pleistocene Ice Age. (A time when much of North America, Europe, and Asia lay buried beneath continental ice sheet.

Earth's climate and the biosphere have been in constant instability, dominated by ice ages and glaciers for the past several million years. We are currently enjoying a temporary reprieve from the deep freeze.

Approximately every 100,000 years Earth's climate warms up temporarily. These warm periods, called interglacial periods, appear to last approximately 15,000 to 20,000 years before regressing back to a cold ice age climate. At year 18,000 and counting our current interglacial vacation from the Ice Age is much nearer to beginning over again.

Global warming during Earth's current interglacial warm period has greatly altered our environment and the distribution and diversity of all life. Here is an example:

Approximately 15,000 years ago the earth had warmed sufficiently to halt the advance of glaciers, and sea levels worldwide began to rise.

By 8,000 years ago the land bridge across the Bearing Strait was drowned, cutting off the migration of men and animals to North America.

Since the end of the Ice Age, Earth's temperature has risen approximately 16 degrees F and sea levels have raised a total of 300 feet! Forests have returned to locations which I might add in geologic history was not so long ago.

During ice ages our planet is cold, dry, and inhospitable, supporting few forests but plenty of glaciers and cold deserts. Like a spread of colossal bulldozers, glaciers have scraped and pulverized vast stretches of Earth's surface and completely destroyed entire regional ecosystems not once, but several times. My best two example of the force from the recent Pleistocene Ice Age come from my hometown area; is Two Creeks Buried Forest in the northern section of Manitowoc County is an example of how fast the ice sheet extended into the region and also Valders Quarry which you’ll find several glacial striations going several directions to be able to count how many ice advances and to what directions they were advancing. Neat Huh!

Anyway, during the Ice Ages winters that went longer and became more severe. The ice sheets would advance and thus grew to tremendous size, accumulating to thickness of up to 8,000 feet! They moved slowly from higher elevations to lower-- driven by gravity and their tremendous weight. They left in their wake altered river courses, flattened landscapes, and along the margins of their farthest advance, great piles of glacial debris. I truly believe Wisconsin is one of the best places to see Glacial Topography left behind from the continental glaciations. Please feel free to see my definitions on my Journal.

During the Ice Age summers were short and winters were brutal. Animal life and especially plant life had a very tough time of it. Thanks to global warming, that has all now changed, at least temporarily.

Global warming over the last 15,000 years has changed our world from an icebox to a garden. Today extreme deserts and glaciers have largely given way to grasslands, woodlands, and forests.

Wish it could last forever, but . . .