Most human-caused greenhouse gas emissions come from a handful of systems: how we make electricity and heat, how we move people and goods, how we grow and waste food, how we manufacture materials, how we heat and cool buildings, and how we use land and forests.
Energy: burning coal, oil, and gas for electricity and heat is still the largest global source of CO₂. Switching to renewables and using energy more efficiently cuts emissions at the source.
Transport: cars, vans, ships, and planes burn fuel. Walking, cycling, public transport, fewer flights, and electric vehicles all help — and so do better city design and freight systems.
Food and land: methane from livestock, nitrous oxide from fertilisers, and carbon released when forests are cleared all matter. Diets, food waste, and protecting ecosystems are climate issues as much as they are nature issues.
Buildings and industry: heating, cooling, cement, steel, and chemicals are energy-hungry. Insulation, heat pumps, circular materials, and cleaner industrial processes reduce the load.
Individual choices matter, especially when many people make them. Systems matter more: clean grids, good public transport, and fair policies multiply what any one household can do. Both belong in the same conversation.
Quick check — 3 questions
Check your understanding — pick an answer, or reveal the correct ones when ready.
1. Which sector is still the largest global source of CO₂?
2. Which of these is a climate-relevant food and land issue?
3. What is the best way to think about individual vs system change?