Before you start shouting at your magazine, don’t worry, you’re not going to read that I think climate change isn’t happening or that human beings aren’t contributing to it. However, I am going to try to show that the version of climate change that we are always being shown may not be all that we should be thinking about.
If you look at the timescale over which human-influenced climate change has been happening – and compare it with geological time – it is such a tiny period. However, people do not live over geological time periods, so it is natural that we concentrate on the present, with little regard for the past. In fact, with today’s human influenced climate change taking up all of the limelight, anyone would think that climate change was solely a human invention and that before the industrial revolution, the climate had been stable. But this is not the case.
A quick glance at Fig. 1 shows massive changes in average global temperature across the millions of years of geological time. The y axis of the graph shows change in average world temperature when compared to today, with the last 150 years’ average world temperature shown as 0oC of change. Immediately, one huge change in temperature can be seen to have occurred between 400 and 300mya, when global temperatures dropped from approximately 6oC above today’s average to about 1oC below. Then, following subsequent fluctuations, both up and down, there was another huge change in average global temperature between approximately 55mya, during the Eocene, and 500,000 years ago, during the Pleistocene. In these cases, global average temperatures fell from approximately 6oC above to 2oC below today’s average global temperature.
It would appear that the world’s temperature then settled down somewhat, but if we examine the graph more closely, we discover two more y axes with different scales to that on the far left. These y axes show that what look like smaller fluctuations as time goes on are actually just as large as the fluctuation between 400 and 300mya. For instance, between approximately 55mya, during the Eocene, and approximately 34mya at the very beginning of the Oligocene, global average temperatures dropped from approximately 12oC above today’s average to only about 1oC above. Then, between 6mya and 500,000 years ago, there was a steady drop in temperature, from 2oC above to 6oC below. Since then, the majority of the time has been spent well below today’s average, with only the increasingly small scale of the graph’s x axis creating the appearance of stability.