Climate Change and Human Activity

William Ruddiman is a paleoclimatologist, that is somebody who studies the climate of long ago and how it influenced and even now influences the world today. He recently retired as the Professor of Environmental Sciences at the University of Virginia and is now the Professor Emeritus in the same department. He has long been known for a series of bold hypotheses about climate change. He was the man who in the 1980s postulated that the rising of the Tibetan plateau created the highly seasonal Monsoonal circulation which dominates the climate of South Asia today.
However today he is best known for his controversial Ruddiman hypothesis. According to this hypothesis Human activity has been a basic and important factor in causing climate change not for the past two hundred years after the Industrial revolution released large amounts of fossil fuels and their byproducts into the atmosphere, but for the last 8000 years during which mankind has changed the face of many regions of the world. He has shown that during the advent of agriculture, large areas of the world including parts of China, the Near East, India and many other regions lost their forest cover. Agricultural land, we often forget is not “normal Nature”, it is a much modified state of the environment. I am sure that if environmentalists existed in those days they would have prevented the development of agriculture in many places of the world! Anyway, these large deforested tracts, where the favoured method of deforestation was burning, followed by irrigation of these tracts led to release of vast amounts of methane and other green house gases in a scale that rivals that of today.

However when Ruddiman looked at the data he found that there were times when the rise of the green house gases in the atmosphere was less and there was even a downturn in the levels of these gases. When he tried to relate these times to known historical events he found that these coincided with times when human activities were curtailed. For instance, two major plague epidemics, the Justinian plague from 640-642 Ad and the Black Death in the 1340s which polished off about 40% of the population of Europe, came to coincide with fall in CO2 levels.
The important thing that this proves is that curtailing human activity can have a profound influence on climate change and this is why it is necessary to vigorously pursue a policy which mitigates and finally reverses the effects of climate change. This theory has been challenged but there is a body of scientific evidence that supports it and it is finding more and more support in scientific circles.
Actually there is a very good example of concerted global action that reversed an important world climate factor. This is of course the Ozone hole. In the 1970s scientists noticed that the ozone layer which protects the earth from UV radiation was developing a hole and this they later established was due to chlorofluorocarbons ( CFCs) which were invented in the 1920s and subsequently used very widely especially in the field of cooling. Most air conditioners, refrigerators and even spray cans were destroying the ozone layer because of their widespread use of this substance. However the world did take concerted and successful action against this problem. The USA banned the use of CFCs in spray cans from 1978, Subsequently at the Montreal Convention the world committed itself to a 1996 deadline to ban the use of CFCs. This has lead to a recovery in the ozone layer and it is likely that by 2050 the ozone hole will have totally healed.
This story emphasizes the fact that concerted global action can change things and it is necessary for the international community to show the same commonality of purpose to deal with CO2 emissions. I believe that sooner rather than later the world will show the will needed to confront the emission menace and will save the earth as we know it.


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