Historically Glacial Periods Far Longer Than Warm Times

There have been five warmer interglacial periods in the last 450,000 years.

In the last 450,000 years there have been only five warmer times, like the one we are enjoying now. And most of the previous interglacial epochs were warmer than the right now.

We are now 11,700 years into the Holocene Interglacial Epoch. No one knows how long it will last. Glacial times are when the earth cools and glaciers grow. Past glaciers have covered all or nearly all of Canada and the northern part of the United States. And the northern parts of Europe and Asia. And the cold grows from the South in South America.

According to Energy Education University of Calgary Over the last 450,000 years, glacials have lasted anywhere from 70,000 to 90,000 years whereas interglacials last approximately 10,000 years.

Figure 1. Grinnell Glacier in Glacier National Park, Montana; photograph by Carl H. Key, USGS, in 1981. The glacier has been retreating rapidly since the early 1900’s. The arrows point to the former extent of the glacier in 1850, 1937, and 1968. Mountain glaciers are excellent monitors of climate change; the worldwide shrinkage of mountain glaciers is thought to be caused by a combination of a temperature increase from the Little Ice Age, which ended in the latter half of the 19th century, and increased greenhouse-gas emissions. From the United State Geological Survey (USGS) a division of the United States Department of the Interior.

USGS employees have taken photos of Grinnell Glacier from this vantage point many times since beginning the Repeat Photography Project in 1997. 

As the glacier gets smaller the Upper Grinnell Lake gets bigger.

The photographer and source is Bailey Willis, courtesy of USGS Photographic Library.