What is 'Radiative Forcing' in flight emissions?

Radiative forcing accounts for the additional warming effects of emissions at high altitudes, such as contrails and nitrogen oxides, which make flying more damaging than ground-level emissions.

Does the train's footprint include the electricity used?

Generally, yes. Calculations usually include the entire life cycle, but even with infrastructure factored in, the high passenger volume and renewable energy use of the Eurostar far outperform aviation.

Is the difference always this large for all flights?

London to Paris is a very short flight where take-off uses most of the fuel. On longer flights, the 'per km' efficiency improves slightly, but the train still remains significantly cleaner for any distance where rail is available.

Is the Eurostar really 90% better than flying?

Yes, Eurostar estimates its carbon savings are up to 96% compared to flying, largely because the French electricity grid is very low-carbon.

transport

Flight vs Train: London to Paris Carbon Footprint Compared

The massive environmental gap between the runway and the rail.

June 5, 2026

Short-haul flight (London to Paris)

63kg CO₂e

per passenger (one way)

Eurostar train (London to Paris)

2.4kg CO₂e

per passenger (one way)

Lower footprint: Eurostar train (London to Paris)

Overview

The journey between London and Paris is one of the busiest travel corridors in the world. As travelers become increasingly conscious of their environmental impact, the choice between hopping on a 60-minute flight and boarding the Eurostar train has become a pivotal decision. While both methods transport you from city center to city center in a matter of hours, their ecological costs are worlds apart.

At first glance, the convenience of flying might seem comparable to the train, but when we look at the carbon intensity of these modes of transport, the disparity is staggering. This comparison evaluates the Greenhouse Gas (GHG) emissions per passenger for a one-way trip between London St Pancras/Heathrow and Paris Gare du Nord/CDG.

The Numbers

The data consistently shows that rail travel is the undisputed winner in terms of efficiency. According to figures analyzed from the UK Department for Business, Energy & Industrial Strategy (BEIS) and Eurostar's own environmental reporting, the differences are quantifiable and significant.

Short-haul Flight: A typical economy flight from London to Paris emits approximately 63 kg of CO2e per passenger. This figure includes "Radiative Forcing" (RF), which accounts for the non-CO2 climate impacts of flying at high altitudes, such as the formation of contrails and nitrogen oxide emissions, which can double or triple the warming effect of the CO2 alone.
Eurostar Train: The same journey via the Eurostar emits just 2.4 kg of CO2e per passenger.

This means that taking the train is roughly 96% less carbon-intensive than flying. Put another way, you could take the Eurostar between London and Paris 26 times before you equaled the carbon footprint of a single one-way flight.

Why the Difference?

The massive gap in emissions is driven by three primary factors: energy source, propulsion physics, and the concept of "Radiative Forcing."

1. The Energy Mix

The Eurostar is an electric train. Its carbon footprint is directly tied to the carbon intensity of the electricity grids in the UK and France. Because France derives a significant portion of its electricity from nuclear and renewable sources, the "grams of CO2 per kilowatt-hour" is exceptionally low. In contrast, planes rely entirely on energy-dense fossil fuels (Jet A-1 kerosene), which release carbon that has been locked underground for millions of years directly into the atmosphere.

2. High-Altitude Impacts (Radiative Forcing)

When a plane burns fuel at 30,000 feet, it doesn't just release CO2. It also emits water vapor and nitrous oxides. At high altitudes, these substances contribute to the formation of cirrus clouds and contrails that trap heat more effectively than they would at sea level. Scientists use a "multiplier" to account for this extra warming. Trains, operating at ground level, do not have this compounded climate impact.

3. Take-off vs. Cruising

In a short-haul flight like London to Paris, a disproportionate amount of fuel is consumed during taxiing, take-off, and the initial climb. Because the cruise duration is so short (often only 20-30 minutes), the plane never reaches its maximum fuel efficiency. The Eurostar, conversely, benefits from the high efficiency of electric motors and the ability to carry hundreds more passengers per trip than a standard short-haul jet, distributing the energy cost across a larger group.

What You Can Do

Choosing the train over the plane is the single most effective "low-hanging fruit" for reducing your personal carbon footprint if you live in Western Europe.

Book in Advance: Eurostar prices can be high, but booking 2-4 months ahead often makes the price competitive with budget airlines.
Consider Total Travel Time: When you factor in airport security, check-in times, and the commute from CDG or Heathrow to the city center, the Eurostar is often faster (approx. 2h 16m) than flying.
Advocate for Rail: Support policies that subsidize rail infrastructure and tax aviation fuel to reflect its true environmental cost.

Understanding your impact is the first step toward meaningful change. To see how your travel choices—from daily commutes to international vacations—stack up, use our tools to visualize your impact.

Estimate your personal footprint at our carbon calculator.

Curious about your own footprint?

Calculate yours →

FAQ

What is 'Radiative Forcing' in flight emissions?: Radiative forcing accounts for the additional warming effects of emissions at high altitudes, such as contrails and nitrogen oxides, which make flying more damaging than ground-level emissions.
Does the train's footprint include the electricity used?: Generally, yes. Calculations usually include the entire life cycle, but even with infrastructure factored in, the high passenger volume and renewable energy use of the Eurostar far outperform aviation.
Is the difference always this large for all flights?: London to Paris is a very short flight where take-off uses most of the fuel. On longer flights, the 'per km' efficiency improves slightly, but the train still remains significantly cleaner for any distance where rail is available.
Is the Eurostar really 90% better than flying?: Yes, Eurostar estimates its carbon savings are up to 96% compared to flying, largely because the French electricity grid is very low-carbon.