With 20th century industrialization it was realized in the late 1970’s - early 1980’s that human induced climate change could be a problem over the next century and by the 1990’s climate change had be come a mainstream science.
Climate change is usually a natural phenomenon, which continually occurs on our planet. It can be a gradual or a sudden process and can be catastrophic. What is discussed in the newspapers is the climate change associated with humanities use of fossil fuels. When burned, these fuels emit the gas carbon dioxide and in turn the carbon dioxide acts to trap the heat in Earths atmosphere in much the same way that heat is trapped in a greenhouse, hence the name the “greenhouse effect”. There are many greenhouse gasses but CO2 is the largest problem and methane CH4 is also very significant. The picture below shows the main greenhouse gasses as they have built up in the atmosphere over time and the relative greenhouse effect they have (the radiative force).
Activities on our planet continually emit greenhouse gases, natural and human induced, and these gases are continually reabsorbed by various processes on the planet. It is the balance of the rate these gases are emitted vs. how fast they are reabsorbed that matters to climate change and the temperature of the planet. Whilst other greenhouse gasses continue to grow in concentration it is the concentration in CO2 that continues to grow significantly year on year, which means it cannot be reabsorbed fast enough by the planet and so will increase the temperature.
Just a back of a fag packet exercise (UK meaning of fag is cigarette), with reference to the graphs, very roughly to maintain a steady atmospheric state to now, the equivalent of about 4ppm of CO2 needs to be removed (or not emitted in the first place). 1ppm of atmospheric CO2 weights 8Gt (8,000,000,000 tons) so 4ppm equates to 32 Gt of CO2, that is 32,000,000,000 tons. This is close to what we output each year from our power plants and other processes. It is clear that we will not be able to stop doing this any time soon.
But what does this number mean? What does 32,000,000,000 tons look like? Just for amusement if we could freeze it as dry ice to make it a solid, shape it into blocks and build pyramids we could build 5000 Great Giza pyramids by weight, if we take density into account the number is nearer 10,000. Convert it to baking soda via a chemical process it would weigh about 60Gt, even more pyramids!
It may surprise you to know that the volumes of greenhouse gasses that are emitted through natural processes massively outweigh the volumes that humanity throws into the atmosphere. However the volumes that the planet can reabsorb naturally is also massive, but not limitless. Prior to industrialization the natural emission from the oceans and living systems was in balance with the planets ability to reabsorb it. Simply put we have now overtaken the planets ability to soak up natural greenhouse gasses together with those produced by industrialization.
Power generation and industrial processes emit about 36Gt (2015) of carbon dioxide each year, and currently this is increasing each year, because we are burning more fossil fuels in spite of renewable energies. Climatologists often present the total weight of carbon that we can add to the atmosphere that limits the global temperature increase to an “acceptable” level of 2oC. This number is 335Gt, at current rates we will be there by 2024. The picture below illustrates this, if you click on the image there is much more information.
Finally I had to have a picture of an outdoor heater in winter as a topic introduction, just to show how daft we can be :) Sorry if you have one, turn it off and go inside please.
Some Useful Linkshttps://www.esrl.noaa.gov/gmd/aggi/