Human activity is changing our climate
IN her recent letter Mrs Jillian Chave writes ‘…I do wonder about how much science actually knows about climate change’. May I reassure her that science knows a very great deal about past, present and possible future climates based on the work of many hundreds of thousands of highly qualified and dedicated people in many different scientific disciplines over a great number of years.
For example, the Ice Age, or in geological terms the Pleistocene Epoch, was a period with many strong and sometimes rapid fluctuations in climate, including major ice advances at a continental scale. It began 2.65 million years ago and ended 11.7 thousand years ago and contained approximately 50 cold and 50 warm stages.
While there is still some debate as to exactly which factors triggered the onset of the Pleistocene Epoch, the advances and retreats of ice sheets during it are well known to have been primarily driven by fluctuations in the receipt of solar energy because of variations in the orbit of the Earth around the sun, the tilt of the Earth’s axis, and the direction it points to (the so-called Milankovitch cycles).
Contrary to what Mrs Chave suggests, science is fully aware of all the natural factors that are at work to affect the Earth’s climate.
It is a matter of fact that if only natural factors were in operation now the planet would be gradually cooling as it has done since the Holocene climatic optimum some 9,000 to 5,000 years ago. The recent rapid, significant and potentially very deleterious rise in the Earth’s temperature has been driven by human activities.
As Mrs Chave finds the topic interesting, may I refer her to the excellent introductory book on the Ice Age written by Professor Jamie Woodward of Manchester University entitled The Ice Age: A Very Short Introduction, published by Oxford University Press, and also to the Royal Society of London and Met Office websites (https://royalsociety. org/topics-policy/projects/climatechange-evidence-causes/basicsof-climate-change/; https://www. metoffice.gov.uk/weather/climatechange/what-is-climate-change) which give excellent explanations of how the Earth’s climate has been and is being changed by human activity.
Professor Bruce Webb Exeter, Devon