Carbon Dioxide (CO2) is the main Greenhouse Gas (GHG) emitted by human driven activities and it occurs mostly from the burning of fossil fuels.
Greenhouse gases (GHGs), such as carbon dioxide, methane, nitrous oxide, and certain synthetic chemicals, trap some of the Earth's outgoing energy, thus retaining heat in the atmosphere. GHGs are good as they trap heat from the sun and keep the Earth habitable for humans and millions of other species. The problem is that human activities have generated excessive amounts of them and they are now drastically out of balance and they are causing the planet to heat. This has extensive implications for life on earth.
There are three types of fossil fuel – coal, oil and gas. Of the three, coal fuels more than a third of the energy consumed worldwide and is the single biggest contributor to climate change. These fuels are non-renewable and currently supply around 80% of the world’s energy.
Fossil fuels are originally formed from the decomposition of buried carbon-based organisms that died millions of years ago. The deposits create carbon-rich compounds that are extracted and burned for energy - fuel.
Fossil fuels are also used to make plastic, steel and a huge range of products. Both these products are increasingly made with other 'feedstock', including recycled products, but most are still fueled by fossil fuels.
Graph Source: Our World in Data