Will the next Ice Age arrive a bit early?

According to the best evidence available coming in the form of ice cores and sea sediments, climate change over the last half million years or so has been a very slow, but steady process.

Ice cores, in particular, have proven to be a gold mine of information for scientists ever since the first one was drilled in 1956 in Greenland. Because the ice has trapped isotopes, air and dust as it formed over the hundreds of thousands of year in areas like Greenland and Antarctica, it has left a concise record that scientists have been able to read almost like a book. In particular, they have constructed a record of CO2 and temperature levels like the one here:

This ice core taken from Vostok, Antarctica shows clearly that much of earth’s history has been spent in icy conditions; what are known as 'glacial periods' that occur about every 150 thousand years (symbol A). The warm periods between these ‘ice ages’ are known as 'interglacial periods' and we happen to be in one of those right now.

The question that interests climate scientists is understanding what factors come into play that trigger the beginning of each period of glaciation. A period of time when both CO2 and temperature levels drop over much of the planet. They want to understand this because its possible that the triggering mechanism might be due, in part, to the effects of elevated CO2. It is troubling to some that while it normally took the earth a period of ten thousand year to build up the CO2 levels by 100 ppm in the past before mankind, it has only taken 52 years to get there with man (see symbol B for level at 2002). In 2011 they have now hit 390 parts per million. The highest ever recorded in over 400,000 years!

One popular theory cites the fact that high levels of this gas in our atmosphere will help to heat up the earths atmosphere (the so-called greenhouse effect). Just look back to our past summer for an example of how hot it felt. This heating causes the poles to melt which, in fact, they are doing as we speak (see Arctic Ice Hits Near-Record Low)! All that fresh water melt off is being dumped into the North Sea and could disrupt the Thermohaline circulation that helps to keep geographic areas of the planet like Europe warmer than they would be otherwise. Once the flow stops, the theory goes, a cycle of ever colder winters will set in that eventually could trigger another ice age. A cycle is set up with more and more continental snow cover that alters the albedo or refractive index allowing more and more solar energy to be reflected back into space. This scenario fits in well with the graph of the ice cores as you can clearly see how both CO2 and temperature profiles rapidly increase before suddenly dropping.

The big question that now arises is will the glacial onset, should it occur, happen slowly (over thousands of years) or might it perhaps be accelerated by the anthropogenic effect of mankind. Only time will tell.

Note: This post did not touch on methane levels, which have also risen to an all time high and which may pose an even greater risk than CO2 in the ability to trap heat. Please see 'The Methane Time Bomb.