It is very hard to be accurate because no one has a measuring stick that is large enough, by the planet earth is in a constant state of emitting carbon dioxide – from natural combustion, volcanoes, respiration of animals, land disturbance and by simple release from the oceans (which also absorb carbon dioxide). Mankind (or would it be more correct to say humanity) is responsible for somewhere between 3% and 5% of annual worldwide carbon dioxide emissions.
Why then, should we be worried about anthropogenic emissions of carbon dioxide which most scientists hold to blame for the rapid recent global warming and their expected future global warming? Whether humans are responsible for 3% or 5% it is simply a tiny amount of the overall carbon dioxide emissions that occur on planet earth.
The reason lies in the carbon cycle. Natural emissions of carbon dioxide are balanced by natural absorption of it. The oceans absorb carbon dioxide, as does vegetation. Humanity, by burning fossil fuel, creates atmospheric carbon dioxide which seems beyond the capability of the oceans and vegetation to absorb, and thus atmospheric carbon dioxide, as a proportion of the constitution of the atmosphere, is rising and has been rising quite drastically ever since the industrial revolution, which is when humanity started burning fossil fuel in serious quantities.
Best estimates indicate that only about 40% of humanity’s carbon dioxide emissions are being absorbed in the carbon cycle by vegetation and by the oceans. As far as we can gather it would normally take our planet’s atmosphere about 5,000 to 10,000 years to increase atmospheric carbon dioxide by 100 parts per million. The last increase of 100 parts per million took just 120 years, so far out of balance iis the natural process of absorbing carbon dioxide.
Now for some simplified facts:-
Amount of suspending carbon in oceans 37,400 GT
Amount of suspended carbon in land biomass 2,500 GT
Amount of carbon dioxide in atmosphere 720 GT
Amount of human carbon dioxide emissions 27 GT
Amount by which atmospheric carbon dioxide is rising each year 15 GT
One gigatonne is a billion tonnes.
Filed under: carbon emissions, climate change, global warming Tagged: | anthropogenic climate change, anthropogenic emissions, atmospheric carbon dioxide, carbon cycle, carbon dioxide emissions, carbon dioxide emissions by source, climate, environment, gigatonne definition, land disturbance, natural emissions, science