Australia Weather News

Geological evidence point to regular "ice ages" in the last million years. During an ice age, the polar regions are cold.

There are large differences in temperature from the equator to the poles, and large, continental-size glaciers can cover enormous regions of the Earth currently habited. Because the Earth has been ice free for the majority of its geological history, many scientists believe we are still in an "ice age" and during this recent event, glaciers have advanced and retreated over 20 times, often blanketing North America and Europe with ice. Our climate today is actually a warm interval between these many periods of glaciation.

The most recent period of glaciation, which many people think of as the "Ice Age," was at its height approximately 20,000 years ago and largely concluded around 12,000 years ago. Jump forward to the last 200 years and we began burning fossil fuels, adding high amounts of CO2 to the atmosphere. As a result, scientists now believe that there will be no new ice age for at least the next 100,000 years.

This is because there are two major factors that led to the onset of the past ice ages – (1) insolation and (2) carbon dioxide levels. Insolation is the term used for how much energy the Earth receives from the sun. This fluctuates over a timescale of tens of thousands of years, because the Earth orbits the sun in an elliptical shape and not a perfect circle. Carbon dioxide concentration is the second component. 200 years ago, CO2 levels were around 280ppm.

As of 2015, levels are now over 400ppm. These two factors can be put into computer models which are then run based on past and current conditions. They then can be extrapolated forward, allowing scientists to make predictions of how ice ages in the future might evolve. This modelling has shown the Earth narrowly missed the initiation of another ice-age in the 19th century, because of the effect of relatively high CO2 levels back then. Even without anthropogenic CO2 emissions, their research shows that the next ice age would have begun in around 50,000 years time. However, additional anthropogenic CO2 emissions has meant we will have to wait an extra 50,000 years on top of this, before ice-sheets begin to build-up again. So, we won't need to lose sleep over this problem.