Climate Change in the Past

When looking at climate change in the past we have to change the focus from short-term studies by climatologists to those by geologists who can predict what previous climates were like using ice cores, the rock record, fossils and other means.

Geology has shown that, millions of years ago, the land masses were in different positions from where they are now. Fossils, or the lack of them, provide a lot of useful information for this period of time.

Over timescales of the last few thousand years, climatic evidence comes from deep in the ice covering Greenland and the Antarctic, or from ocean sediments. This period also covers the existence of human beings, whose ways of life have partly been influenced by climate. Tree rings, river sediments and changes in glaciers provide evidence of changes in climate over hundreds of years. It is only for the last 150 years or so that instrumental records are widely available and these are only over certain parts of the world.

There is little doubt, from the evidence so far, that there have been enormous changes in climate. These ranged from a complete absence of ice over the Poles to ice sheets extending across much of Europe, Asia and North America. The last major extension of polar ice retreated only 10,000 years ago. Since then, the climate has sometimes been warmer and sometimes cooler than it is now.