To Marrakesh by train - Part 5: notes on carbon emissions (and comparison with flying)

January 19, 2026

To Marrakesh by train - Part 5: notes on carbon emissions (and comparison with flying)

So, is it worth it to avoid flying when travelling long distances?

When I travel long distances by land, for example, from the Netherlands to Portugal, people often ask, why? This post will make it clear. In the last post I wrote about how we travelled without flying from the Netherlands (via Porto) to Marrakesh and back. In this post, I will show the difference it makes for emissions.

But first, why should we care about emissions?

Image from "Show your stripes", Prof. Ed Hawkins (University of Reading) .

This image is a representation of the average temperature in the planet since 1850 until 2024. Each stripe represents the temperature of one year. Dark blue represents colder temperatures, and dark red the warmer temperatures. These images, can be produced for any place where there are registries of historic temperatures. For example, this is the one for Portugal:

This other graph below is what it actually represents. If we consider the average temperature between 1961 and 2010, and then plot how much warmer or cooler the temperatures were every year, in relation to that average, from 1850 until 2024, we get a good idea of how the average temperatures have been increasing.

We all know that the main cause of increasing temperatures are the greenhouse gas emissions that are released when burning fossil fuels. But where did fossil fuels originate?

My favourite description is the one from Rebecca Solnit in a chapter of the book "Orwell's Roses". Here she describes the origin of coal:

"Most of the coal came into existence in the Carboniferous, which lasted between 359 to 299 million of years ago. […] It was an alien planet, long before flowering plants, long before mammals…” In that period the continents were not like we recognize them today. But the land around the Equator was full of plants, giant mosses, ferns, primitive trees. ..Usually when plants die, the carbon they took up returns to the atmosphere through decay, and forms again carbon dioxide. But in this period, the dead plants drowned in swamps and became peat. Which through millions of years became coal [...]"

"Think of the Carboniferous as a 60 million year inhale by plants, sucking carbon dioxide from the sky, and the last 200 years as a monstruous human-engineered exhale, undoing what the plants did so long ago."

Rebecca Solnit, Orwell's Roses

This quick burning of long buried material, releasing emissions that warm up the planet, has numerous consequences. Some impacts we are already experiencing, like the accelerated melting of glaciers, the increase in the frequency of catastrophic climate events, droughts, floods, forest fires, more harvest failures. But other impacts, we are not sure yet when they will hit, like the slowing down of the Atlantic Ocean current (AMOC), which is responsible for the mild climate we experience in Europe. Even if it seems for now as if not much is changing, the consequences of this drastic temperature increase, is not something that either ecosystems or humans can easily adapt to, and would mean massive catastrophes and disruptions. That is why reducing emissions is key.

Now, back to our trip.

We noted down the kilometres we travelled by train, bus, ferry, walking and car, and then calculated the emissions caused in our trip. Two things were striking: the amount of emissions from the car, and the comparison with flying. Of course, these are things we know in general, but seeing the numbers is still shocking.

Here you can see the travelled kilometers per mode of transportation. We did about 4700km by train, about 1500km by long distance bus travelling (coach), around 1300km by car (which we rented in Morocco), 120km walking and 80km by ferry.

Now, when we look at the emissions we caused (per person) per transport mode, here is the result. The car has way higher emissions than the train even tough we travelled much more by train.

This is even more visible when we plot it in this way. On the graph below you see the share of kilometers travelled per each mode, and the share of emissions per mode. Even though the car was only used for 17% of the travel distances, it caused more than 60% of the emissions. The train, on the contrary, was used to cover 60% of the distances but caused just over 20% of the emissions.

But the greatest difference comes if we compare the trips we did by train and coach bus with flying. In this graph we show how the emissions would compare if we had flown the kilometers that we did by train and long distance bus (with the caveat that this might overestimate a bit the kilometers in some of the routes we did).

If we had travelled the long distances by plane (gross estimate) we would have emitted almost 1ton of CO2 per person. Like this, we emitted in total 240kg of CO2 per person in the whole trip.

The value of 1ton of CO2eq emissions, seems rather high compared to what Google flights estimates for a flight Amsterdam-Marrakesh: about 200kg per passenger per flight. This could be partly because we overestimate the kilometers by airplane, as our kilometers travelled were by land, not in a straight line, and had in fact, several stops: Porto, Tangier, Marrakesh and San Sebastian. The direct flight to Marrakesh would not cover the same travel route.

However, another argument is that common carbon calculators for flights seem to underestimate the emissions caused, as brought up by this article. They tend to assume the optimal route, not the actual travelled routes, nor the time spent taxiing before take-off and after landing, and to neglect the effect of contrails and other emissions. Contrails are the condensation trails made of water vapour and other gases exhausted from the airplane engines, which can look very pretty in the sky, but might contribute to greater warming than the direct CO2 emissions.

But what is 240kg of CO2 emissions? With the help of this convertor , we can see that it means 4 tree seedlings growing for 10 years, or charging 19,000 smartphones.

For a longer discussion on the environmental impacts of aviation and the importance of reducing it, check the website of Stay Grounded. They publish reports on these topics, and here, for example, they present a summary of their arguments.

Note: For the calculations, I looked up values of CO2eq emissions per km travelled per passenger (in grams), from different sources. Here you see the values used, the references and assumptions.