Ice time

In 1815 a volcano erupted on the island of Sumbawa. This eruption through clouds of ash and dust into the air, blocking out the sun. This had the consequence of making a mini ice age for the world. Crops failed to grow and there were outbreaks of disease. Globally the temperature had only fell by one degree. This shows how delicate the temperature of the earth actually is.

Scientist knew there is something strange about the past. For example arctic animals remains in warm climates or boulders stranded in impossible places. Geologist James Hutton was the first to theorize wide spread glaciation, unfortunately his ideas where ignored. Common peasants, not corrupted by science, knew that glaciation was the cause of these strange events.

A naturalist called Louise Agassiz embraced this theory. While at the post of professor of natural history Agassiz friend Karl Schimper first came up with the term ice age and showed that there is good evidence to show that ice covered much of Europe, Asia and North America. Louise and Karl swapped notes which lead to Louise getting much of the credit that Karl felt should be his own. Agassiz then travelled spreading his theory around the world but everywhere he went he found reluctance to accept his theories. It took a while but eventually people accepted wide spread glaciation. But what causes ice ages?

James Croll a janitor at Anderson’s university published a paper in the philosophical magazine in 1864, which was recognized as work of the highest standard. His paper was about how earth’s orbit might have an impact on how ice ages start. Croll was the first to suggest that shape obit of the earth, circular to oval and back, might have an effect on the start and end of ice ages. Thanks to Croll people in Britain started to accept the ideas of ice ages more readily. Sadly the ice age theory fell out of fashion it was ‘to be rejected without hesitation’ in the words of Agassiz’s successor.

One of the difficulties that caused this was that Croll’s calculations meant that the last ice age had to be only 80 thousand years ago whereas geological evidence shows that the last ice age was much more recent than that. The theory was saved by an academic by the name of Milutin Milankovitch. He thought that more complex cycles in the astrological orbit of the earth are responsible for ice ages coming and going. These cycles being tilt, pitch, and wobble which have a profound effect on the earth’s temperature. He spent the next 20 years calculating the angle and duration of incoming solar radiation at every latitude on earth, in every season, for a million years, adjusted for three ever changing variables. Eventually he wrote a book in 1930 called mathematical climatology and the astronomical theory of climate change. He thought that, like most people, it was a gradual increase in harsh winters that result in ice ages. Meteorologist Wladimir Koppen saw that it was more subtle than that.

Koppen found out that the cause of ice ages was because of cool summers and not harsh winters. If all the winters ice wasn’t melted by the summer, he found, more heat from the sun will be reflected back causing overall cooler temperatures globally. ‘It is not the amount of snow that matters’ said Gwen Schultz ‘but that the snow lasts’. This can cause ice ages. In the 1950’s scientist where unable to associate Milankovitch’s cycles to ice ages. Sadly because of this Milankovitch died before he was able to prove his cycles were correct and his calculations fell out of fashion.

We are actually in a small ice age at the moment. Having both poles frozen over is a unique situation for the earth. In fact at the height of the last ice age 30% of the world was covered in ice, 10% still is today. Earth usually has dramatic changes from hot periods with no ice, then plunges into an ice age with glaciers everywhere. There is no reason that this period of fine weather that we live in should continue for any longer, there is every reason that is should tip into freezing cold or much too hot. We live on a knife edge.

Ice ages are not bad things for the planet. They grind up rocks leaving rich soil and scrape out fresh water lakes. They shape the planet into how it is today. Tim Flannery once said ‘there is only one question needed to ask of a continent to determine the fate of its people “did you have a good ice age?”’