mcld.co.uk

I've been doing a lot of academic travel recently: conferences, project meetings, workshops, PhD exams. Luckily, I've been able to do almost all of it by train, even though I've been to more countries than I can easily count!

Here I want to list these and make an approximate carbon footprint calculation, comparing it against the equivalent if I was flying everywhere. I've done these calculations before, but since I've made dozens of trips recently it's useful to show it and give a real-life example of what we do and to what extent it matters.

So! Here is a list of the academic travel I did in 2024 and 2025, with the reason for travelling, and the carbon footprint if I was flying. Then, I will compare those footprints against those for what I actually did. In most cases I took the train. Sometimes a boat (especially for the UK). For two of these I did fly part of the way, and I'll mention that in the table.

I live in the Netherlands. I'm going to leave out the trips to the Netherlands and Belgium, because it's simply inconceivable that someone would fly those! I will also omit the events I declined or attended online.

In this table, the numbers are the hypothetical footprint of flights I did not take:

Now, in most cases what I actually did was take the train. Using a carbon-footprint calculator I worked out the footprint for these, and surprisingly, it often comes out as approximately 10 kg CO2e, irrespective of how long the trip is! This is because of the different types of train: to go all the way to Sweden I took very efficient ICEs, while to go to Oxford I took a local train, plus a Eurostar, plus another local train, and it appears to add up to a similar amount. So, for simplicity I'm going to assume each train trip was 10kg. Since it's at least ten times smaller than the flight footprint, this approximation is acceptable.

The two trips I've marked with asterisks* are the ones where I part-flew. Even if you can't take the train all the way, it's better than taking lots of hopping flights. Here's what I did:

• For Norway in 2024, I flew to Oslo and then took the train to Trondheim. It would have been 316kg to fly direct (and even more to fly indirect!), but I managed at least to reduce this one to 264kg by taking the beautiful Oslo-Trondheim train ride.
• For Finland in 2025 - it takes a long time by train from the Netherlands, of course! I was able to make the most of it by combining a conference in Sweden with the event in Finland. So this is a "triangular" two-stop trip and that's how I've calculated it. I flew back on the return, meaning my actual footprint was around 720kg rather than the max of 1277kg.

If you add up all those hypothetical flights in the table above -- and, just to remind you, those are flights I did NOT take -- you get 6959kg over 2 years, about half of an average EU citizen's "personal" footprint for the same time. So it's a notable amount. What I actually incurred was 1104kg, reducing it to about 15%.

It's a definite saving. Of course it's way above zero, it's an amount worth thinking about. (I won't comment here on switching to online attendance - I've written about that before and it would take too many words.) Note that this is not only an estimate, it's also an incomplete picture: not least because it ignores online events, and local events. I mainly want to see what was the impact of my choice not to fly on these business trips.

I think it's important to remember that we're aiming to change the system, we're not aiming to guilt-trip individuals. So the wider lesson is that grounded academic travel is possible, it makes a genuine difference -- approximately an order of magnitude reduction! -- and we need to support it (in the departments, in funding, and when you organise a conference).

This post was partly inspired by Rebecca Nordquist's post describing similar experiences. As noted by Rebecca, these long train trips are often also your "best day in the office" for some quiet work!