What CO₂ emissions are
Carbon dioxide is a colourless, odourless gas. It is naturally part of the carbon cycle, but human activity — chiefly burning coal, oil and gas — has pushed atmospheric concentrations from around 280 parts per million before the Industrial Revolution to over 420 ppm today.
Where they come from
Global share by sector, from the IPCC and IEA:
- Electricity & heat — about 30%
- Transport (road, air, sea) — about 20%
- Manufacturing & industry — about 20%
- Agriculture & land use — about 18%
- Buildings — about 6%
- Other energy — about 6%
What they cause
CO₂ acts like a blanket: it lets sunlight through but traps the heat that bounces back. Higher concentrations mean a warmer planet, which causes more frequent heatwaves, stronger storms, longer droughts, rising sea levels, ocean acidification and large-scale shifts in where species can live.
How to reduce CO₂ emissions
The actions with the biggest per-person impact, ordered by tonnes saved per year:
- Cut a long-haul flight — saves 1.5–4 t CO₂e per return trip.
- Switch from a petrol car to an EV (on a clean grid) — saves about 1.5 t/year.
- Switch electricity to a renewable tariff — saves 0.5–1.5 t/year depending on country.
- Move to a largely plant-based diet — saves about 0.8 t/year.
- Insulate the home and upgrade to a heat pump — saves 1–3 t/year.
See your own number with the carbon footprint calculator, then track the changes you make with the carbon tracker.