1. A greenhouse gas is a gas in an atmosphere that absorbs and emits radiant energy within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in Earth’s atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone.
2. Without greenhouse gases, the average temperature of Earth’s surface would be about −18 °C (0 °F), rather than the present average of 15 °C (59 °F).
3. Human activities since the beginning of the Industrial Revolution (around 1750) have produced a 40% increase in the atmospheric concentration of carbon dioxide (CO2), from 280 ppm in 1750 to 406 ppm in early 2017.
4. It has been estimated that if greenhouse gas emissions continue at their present rate, Earth’s surface temperature could exceed historical values as early as 2047, with potentially harmful effects on ecosystems, biodiversity and the livelihoods of people worldwide.
5. Much like the glass of a greenhouse, gases in our atmosphere sustain life on Earth by trapping the sun’s heat. These gases allow the sun’s rays to pass through and warm the earth, but prevent this warmth from escaping our atmosphere into space. Without naturally-occurring, heat-trapping gases—mainly water vapour, carbon dioxide and methane—Earth would be too cold to sustain life as we know it.
6. The danger lies in the rapid increase of carbon dioxide and other greenhouse gases that intensify this natural greenhouse effect.
7. For thousands of years, the global carbon supply was essentially stable as natural processes removed as much carbon as they released. Modern human activity—burning fossil fuels, deforestation, intensive agriculture—has added huge quantities of carbon dioxide and other greenhouse gases.
8. Today’s atmosphere contains 42 per cent more carbon dioxide than it did at the start of the industrial era. Levels of methane and carbon dioxide are the highest they have been in nearly half a million years.
9. Carbon dioxide is the main contributor to climate change, especially through the burning of fossil fuels. Methane is produced naturally when vegetation is burned, digested or rotted without the presence of oxygen. Large amounts of methane are released by cattle farming, waste dumps, rice farming and the production of oil and gas.
Behind the struggle to address global warming and climate change lies the increase in greenhouse gases in our atmosphere.