Monthly talk: Peter Lewis – Ice ages and climate change
Our guest speaker in February was Peter Lewis. He has spent his career in many different sectors of education, including in the army and the prison service. Throughout, he has maintained his interest in earth sciences such as geology and geography. His chosen topic was an enormous and challenging one, and most members of the audience had to work hard to keep up with the complex issues he explained. It would be an impossible undertaking to summarise all that he had to say here!
While most of us are aware that the earth has experienced widely contrasting climatic conditions throughout its history, I suspect that few of us have a grasp of why these changes occur. Peter focussed on six primary factors in this – the role of the sun, the earth’s place in the solar system, the land, the oceans, the atmosphere and the impact of mankind.
Peter outlined how it was as recently as the 19th century that scientists came to realise that the earth had experienced ice ages. Furthermore, systematic keeping of meteorological and climate data, knowledge about the jet stream and other phenomena are quite recent developments. They have enabled scientists to understand what has happened in the past and what may happen in the future.
We now know that rather than ‘the ice age’, the earth has experienced a considerable number of ice ages, and in fact it might be argued that these are nearer the norm for our planet than periods of warmth. Many of these earlier ice ages lasted for many millions of years. More recently, in the past 2-3000 years, there has been a cycle of ice ages alternating with periods of considerable warmth. We know, for instance, that the Romans were able to grow grapes and other ‘Mediterranean’ crops in this country, and the same was true in the Middle Ages, but in between times there were periods when agriculture was very challenging because it was so cold. There was certainly a significant ‘mini ice age’ in the 16th and 17th centuries recorded by diarists and artists who depicted the Thames frozen over, and hard winters were the norm.
These variations occur naturally, and are the product of the frequency of sun spots, the changing tilt of the earth in its orbit around the sun, changes in the proportion of land and sea on the earth’s surface, variations in the salinity of the oceans and other factors. These have profound effects on the currents in our oceans, air temperatures, and which plants and animals can thrive.
Of course, in recent centuries, the activities of mankind are making a significant impact as well, and this continues to be a major issue for us all in our own lifetimes. Peter’s view is that while we need to take action at present to anticipate major changes in our environment, our way of life and for life on earth, it is also the case that there will be another ice age in about one or two millennia, such is the power of the forces which are beyond mankind’s control. Time will tell.
The guest speaker at our next meeting on Monday 16th March is local writer Stephanie Austin who will be speaking to us about ‘Turning to Crime in Retirement’. I hope you will all come ready to take notes!
John Vick