Greenhouse gases are released mainly through the use of fossil fuels such as coal and petroleum.
Industrial processes and livestock farming are also relevant emission sources.
The primary greenhouse gases in the Earth’s atmosphere are:
Water vapor is the most abundant greenhouse gas, but most scientists believe that water vapor produced directly by human activity contributes very little to the amount of water vapor in the atmosphere.
Rising levels of greenhouse gases warm the earth's atmosphere, leading to climate change.
Global warming has diverse negative impacts such as rising sea levels, increased risks of flooding, drought and other extreme weather events.
Thus at the 2015 Climate Summit in Paris the international community agreed to limit the temperature increase to 1.5 °C when possible and to keep it below 2 °C.
This can only be achieved if global greenhouse gas emissions are rapidly reduced.
During the 20 000-year period before the Industrial Revolution, atmospheric CO2 fluctuated between about 180 ppm during ice ages and 280 ppm during interglacial warm periods.
Since the beginning of the Industrial Revolution in the 1750s, the amount of CO2 has risen nearly 50%, according to NASA’s Global Climate Change portal.
Today, CO2 levels stand at over 410 ppm.