Ice Ages have played their part in the history of the Earth for billions of years. It is estimated that there have been at least 50 ice ages in the last 3 billion years. We know this is probably correct through the evidence collected from geological sources. With all the news about climate change and global warming, it is a subject which has taken on a higher level of importance. But, why do they appear and disappear?
Like most things meteorological, there is no one simple solution. It is said that predicting the weather accurately is one of the most difficult calculations we can ask of computers. Believe it or not, weather forecasting today, is on the whole pretty accurate. Satellites and high-power computers as well as various weather stations around the planet all help to make sense of the millions of variables involved.
The probable and possible reasons why we experience ice ages include the following complicated and interconnected mechanisms; some occurring in our world and others out into space. If we begin with the latter, the Earth’s orbit around the Sun decides how much heat we get from our star. Our solar orbit is not constant. It moves from nearly circular to elliptical over what we think is a 96,000-year period. That means that sometimes we are closer to the Sun and at others further away. The reason for this change is due to the gravitational effects of the largest planet in our solar system, Jupiter. Over this period, it pulls the Earth out of orbit a little and then lets it return.
We are all aware of the seasons we get each year. This is due to a “wobble” in the orbit of the Earth throughout each year. Taking the UK as an example, when the planet tilts twenty-three and a half degrees towards the Sun, it is mid-summer and when tilted the same amount away from the Sun, it is late December when it is usually cold. The reason for this wobble we think was caused by a celestial body coming very close to us in the distant past or some form of collision. But, it does not stop there, literally. Over 41,000 years this angle of tilt changes which affects how much heat the Earth receives.
We are not finished with wobbles either. There is a third wobble in the Earth’s orbit due to angular momentum. It has the effect of making the Earth’s axis wobble. The period of this cycle is 20,000 years.
Moving from space to the Earth, we are now beginning to understand how important the makeup of the atmosphere is. As carbon dioxide rises our climate gets warmer. Although today’s rise is mainly due to us, in the past, volcanic eruptions have been responsible for polluting the atmosphere so badly that it has cut down the amount of light and heat reaching the surface. By the same token, any decrease in carbon dioxide in the atmosphere will cause the temperature to fall.
If you ever doubted how powerful the effects of our climate change are having on our climate by pushing more carbon dioxide into the atmosphere, then think about this: We have likely already delayed the next ice age by about 100,000 years!
John Pullen 