CO2:

carbon dioxide, a gas in Earth’s atmosphere. It occurs naturally and is also a by-product of human activity such as burning fossil fuels and land-use change. It is the principal anthropogenic greenhouse gas.

Climate change:

a change in the climate’s mean and variability for an extended period of decades, or more

Fossil Fuels:

biomass lain down in the Earth millions of years ago, such as coal, oil, and natural gas, which when burnt produce carbon dioxide.

Global warming:

a rise in the Earth’s temperature, often used with respect to the observed increase since the early 20th century.

Greenhouse gases:

gases in the atmosphere, which absorb thermal infra-red radiation emitted by the Earth’s surface, the atmosphere and clouds e.g. water vapour, carbon dioxide, methane and nitrous oxide.

For more information please check Met office: Climate change glossary