The Effect of Humans on the Carbon Cycle
Over the past 200 years, humans have started to have a measurable effect on the carbon cycle. Part of this is due to deforestation. If we look at biomass per acre, forests contain the highest density of biomass on the planet. So deforestation removes carbon from biomass, and where do you think it goes? Some of it is turned into wood and paper products, but a lot of it has gone into the atmosphere.
However, an even bigger change to the carbon cycle has occurred as a result of the widespread use of fossil fuels. Burning fossil fuels releases carbon dioxide, also known as CO2, into the atmosphere. This adds carbon that has been out of circulation for millions of years directly to the atmosphere.
The immediate result of these human activities is that in the past 200 years, the concentration of carbon dioxide in the atmosphere has dramatically increased. In 1800, the carbon dioxide concentration in the atmosphere was about 280 parts per million, but the most recent readings from June of 2012 measured the concentration at 395 parts per million. Scientists measure carbon dioxide in the atmosphere in parts per million, which is another way of saying, ‘Out of every million molecules of air, how many are carbon dioxide?’ If 280 molecules out of every million are carbon dioxide, then the air has a CO2 concentration of 280 parts per million, or ppm.
In 1958, scientists started taking direct measurements of atmospheric CO2 on a continuous basis. From these direct measurements, we know that the concentration of carbon dioxide has been steadily increasing year after year for the past 54 years in a remarkably regular seasonal pattern. The pattern is so steady that CO2 levels have reached a new high each May for the past 46 years straight.
EPA’s Climate Change Indicators (2014)
The concept and science of Climate change by Glory Oguegbu