The real scale of aviation emissions
Aviation accounts for about 2.5% of global CO2 emissions, but the climate impact is higher because of non-CO2 effects (contrails, water vapour) — the total warming impact may be 2-4 times the CO2 contribution alone. A return long-haul flight is typically the single largest component of a person's annual carbon footprint.
What genuinely helps
Fly economy. Business class uses approximately 4 times as much cabin space per passenger. On a direct long-haul flight, flying economy is meaningfully greener.
Fly direct. Taking off and landing are the most fuel-intensive phases of flight. A direct return London-New York produces around 0.67 tonnes of CO2 equivalent per passenger. A connection via a hub can add 20-30%.
Consider the alternatives. The Eurostar from London to Paris takes 2h20min and produces roughly 90% less CO2 than flying.
On carbon offsets
The voluntary carbon offset market has a troubled track record. Studies have found that many offset projects would have happened anyway, or have subsequently reversed. Demand reduction and cleaner technology are more reliable than offsets.