Carbon emissions are greenhouse gases that trap heat in the atmosphere and warm the planet. They are released into the air by burning fossil fuels, such as coal, oil, and natural gas, as well as by decomposition and ocean release. The concentration of these gases in the atmosphere has increased significantly since the beginning of the industrial revolution, and has reached levels not seen in more than 3 million years.
These increases in greenhouse gas (GHG) emissions are caused by human activities, including deforestation and the burning of fossil fuels. This increase has been accompanied by a rise in global temperatures.
The atmospheric concentration of carbon dioxide has now risen to 280 parts per million – this is far above the range that has prevailed over most of the 800,000 years of history that humans have existed on earth. Carbon dioxide levels have risen at a fast pace since the start of the industrial revolution.
Until recently, the atmosphere contained only 200 to 280 molecules of CO2 for every million molecules of air. At this level, the CO2 was naturally absorbed by plants and trees through photosynthesis. The soil also absorbed some of the gas through microbes that bind it to organic matter. These carbon sinks kept the atmosphere in a relatively stable state for thousands of years.
Now the rate of global carbon emissions has accelerated again and, if we continue to burn fossil fuels at current rates, by the end of this century they will reach 75 billion tons a year. This will increase atmospheric concentrations to 800 ppm or higher – levels not seen on Earth for 50 million years. Observations of the isotopic fingerprint of CO2 in the modern atmosphere provide clear evidence that our industrial activities are responsible for this rise in concentration.