I inherited from my Glaswegian great grandfather a book containing a long account by Joseph Black, then professor of medicine in that city, of his original experiments on medicines used for indigestion in which he found that magnesia and lime water, when treated with acid, gave off a gas which he called ‘fixed air’. The date was 1754. He had discovered the first gas other than air itself, one that he showed did not support life and that, after John Dalton described his atomic theory in 1805, became known as carbon dioxide, CO2.
After Black, in 1775, came Joseph Priestley in England and Carl Scheele in Sweden who co-discovered oxygen, and then the Lavoisiers in Paris who were able to show how animal life depended on converting oxygen into CO2 to release energy. As we have watched the Olympic Games, we have seen a dramatic illustration of this miracle of nature as the athletes gasp in air in the hope of producing enough energy to win their races. More soberingly, we have watched with horror as wildfires consume oxygen and pour out smoke and CO2.
The role of trees and other plants in the story of life was eventually worked out by the German, Justus von Liebig, in the 1850s. He showed that they do the opposite, using sunlight to convert CO2 into oxygen to provide the chemical energy required to grow and reproduce, thus completing the carbon cycle on which life on Earth depends. Liebig also showed the importance to plant growth of nitrogen (a gas which was discovered by Black’s pupil, Daniel Rutherford, who became professor of botany in Edinburgh), leading to the production of artificial fertilisers and enhancing the continuing Agricultural Revolution.
Our Stone Age ancestors learned how to provide energy for warmth and cooking by burning wood, and the later widespread use of charcoal then fossil plants (coal, peat, oil and natural gas) allowed the Western economies to dominate the world’s economy in the Industrial Revolution from the late 18th century. Central to this were the concept of capitalist economics in Adam Smith’s The Wealth of Nations and the significant improvement of the steam engine by James Watt, both published in 1776 while they were working in Glasgow. Great benefits to mankind ensued, but also the seeds of climate change had been sown â in Scotland â and the plant was nourished by our coal and oil; we therefore have a moral responsibility to set an example in the management of its adverse consequences.
The scientific recognition of the harmful atmospheric consequences of the use of fossil fuels, long appreciated by citizens of polluted cities, can probably be dated to the experiments of the Irish scientist John Tyndall, working in London in 1859. He was investigating why the Earth’s atmosphere keeps the planet warm and showed that radiation from a heat source is absorbed by some gases but not by others. Gases comprising a single element, like oxygen and nitrogen, did not absorb the heat whereas compounds such as carbon dioxide, water vapour and nitrous oxide did. He proposed that the atmosphere allows radiation in, but it changes on absorption and some of what is reflected back into space is trapped. This turns out to be why life has developed alone on this planet in our solar system, but the downside is that the more carbon dioxide in the air, the higher the temperature unless there is some regulatory mechanism.
The natural control of carbon dioxide levels in the air is the balance between production by animals and removal both by plants and by dissolution in the oceans. This has been distorted since the Industrial Revolution, most particularly over the past 100 years by the exponential increase in the Earth’s population and its hunger for energy. Removal by water (CO2 is an acid in solution) causes the upper layer of the oceans to acidify and become less able to absorb it. Meanwhile, removal by vegetation is impaired as we continue to cut trees down and allow them to burn. And this, in a tiny nutshell, is why we are where we are, suffering from the effects of a poisoned planet, now showing serious signs of distress.
First, I should explain why I think that what each of us does matters. There are only two ways of dealing with this crisis, and we have now reached the point when the changes are accelerating and threaten to be irreversible; we must dramatically reduce production of CO2 and we must also find ways of reducing it from the expected even higher concentration in the atmosphere. Both are essential, and the first is down to us all.
Think what your and my roles are in the production of CO2 (for the purpose of this I am ignoring other greenhouse gases). Throughout the day, we each breathe out about 500 litres of CO2. This weighs about one kilogram or 0.365 metric tonnes per annum and is part of the natural carbon cycle. There are almost eight billion of us and rising, so we certainly need those trees and oceans. If we are overweight and unfit, we produce more, as we do when we exercise, though the latter will reduce the former two and is on balance a good thing.
Burning fossil fuel is what puts this CO2 out of natural balance. We do this when we use electricity, oil, or gas to warm and light our house or workplace, to cook and run our computers and other apparatus, and to drive our car, unless the electricity is from a renewable source. We also do it indirectly with other travel, our purchases, and our production of waste. When you add up all these normal personal activities, you get your individual carbon footprint.
In terms of population fossil fuel CO2 production, every individual in the world is estimated to produce on average about 4.3 metric tonnes (4.74 US tons â a US ton is about 1.1 tonne, and a tonne is about 0.98 imperial tons) each year, but there is huge variation around this average. In 2016, the world’s greatest polluters were China (produced 10.43 billion US tons), USA (5.01), India (2.53), Russia (1.66), Japan (1.24) and Germany (0.78). The UK came 17th in this table with 0.379 billion US tons and had reduced this to 0.358 billion in 2020.
However, hidden within these statistics are the individual contributions â per head of population. Here Kuwait and the UAE top the table at 25.62 and 23.37 US tons per person each year respectively. In the USA, the average person contributes 15.52 US tons and in UK 5.5 US tons. As you would expect, the poorest countries tend to produce much less; for example, Indian individuals average 1.91 each compared to Chinese at 7.38 US tons. We in the UK are just in the lower half of the European league.
Each average conceals huge differences between the wealthy and the poor people in a population, as the greater your wealth, the more you will be likely to contribute â big house, expensive tastes, two cars, several annual long-distance holidays, etc. For example, driving an average-sized car for 5,000 miles will easily produce a ton of CO2.
For the UK to reach net zero emissions, we all need to aim towards zero ourselves, as well as urging our governments to contribute to international efforts to find solutions; these all lie in the broad realm of physics. So, the first challenge is to reduce our carbon footprints, and we need to get on with it. You can easily calculate your own approximate carbon footprint at www.carbonfootprint.com, using information on your consumption, use of transport and fuel expenses.
We all have an uneasy feeling that we are not doing our bit and have lots of excuses, but it is time to think of our successors, our children, and of all others wherever they live on this planet. We can see what life will be like for many already; it is shown daily on the television as it is happening now in many places. If you are young, it will be easier as your footprint is likely to be low and it will largely involve adjusting your aspirations. If you are old and set in your ways like me, it is harder; I know because I have been struggling with it now for over a decade. I shall leave you to ponder how you might approach this until next week.
Anthony Seaton is Emeritus Professor of Environmental and Occupational Medicine at Aberdeen University and Senior Consultant to the Edinburgh Institute of Occupational Medicine. The views expressed are his own