Buoy II: AIR:
Air is made up of oxygen, nitrogen, carbon dioxide and water vapour. The chemical composition of our modern day atmosphere is vastly different to how it began. It is currently composed of 78% Nitrogen (the most abundant but inert gas), 21% oxygen (the part we need to breathe), 0.9% Argon, 0.04% carbon dioxide and 0.06% other gases. Until the beginning of the last century, the Earth’s atmosphere was relatively constant. Plants took up carbon dioxide, made food and released oxygen into the air. Animals took up oxygen to breathe and released carbon dioxide into the air. Things were in balance. When plants died their remains accumulated over millions of years as fossils giving rise to coal and oil - 'fossil fuels'. Burning these in the last hundred years has destroyed that balance.
With the rise of industrial activity and the burning of fossil fuels, the level of carbon dioxide in the atmosphere increased considerably, as also have methane, CFC’s and nitrous oxides. These are known as the greenhouse gases and cause Climate Change. Both methane and CFCs, despite their low concentrations make a large contribution to global warming and are the most important after carbon dioxide.. One positive note that following the banning of CFCs they have started to decline in the atmosphere but methane is increasing as the polar icecaps melt and methane is released. Currently methane is close to 2ppm up from a stable value of about 0.7 ppm before the 1700s. The photo above is from the NASA weather satellite which can observe and measure components of the Earth's atmosphere. For more information visit https://research.noaa.gov/ and https://science.nasa.gov/earth/