Climate Change
Greenhouse gases (GHG) are all examples of variable gases – those gases which exist in different amounts across time and space. One of the mechanisms through which GHG have changed in their atmospheric concentrations is through human activity.
Human processes have greatly increased the amount of greenhouse gases in Earth’s lower atmosphere. Since the start of the Industrial Revolution in the 19th century, humans have been releasing large quantities of these gases into the atmosphere, most as byproducts of using fossil fuels like coal, natural gas (methane), and oil.
As a result, more of Earth’s emitted heat energy is being absorbed by the lower atmosphere and less of it is escaping to space. This is the underlying cause of human-induced climate change.
Since the start of the Industrial Revolution in the 17th Century...
- Carbon Dioxide concentrations have increased 30%, and is the most significant GHG directly affected by anthropogenic activity.
- Methane concentrations have increased by 145% in that time. Although there is less methane in the atmosphere than carbon dioxide, methane is a far more potent GHG: a single methane molecule can trap 20 times as much heat in the atmosphere as carbon.
- Nitrous oxide concentrations have increased by 15%
The graph below shows what the major sources are for greenhouse gas emissions by sector, as well as showing them for carbon dioxide, methane, and nitrous oxide separately. Look closely and consider what sectors seem to have disproportionate levels of responsibility for GHG emissions. Do any of them surprise you?