Why I took the train to #HLF19

In her acceptance speech for the Abel Prize in 2019, Karen Uhlenbeck made an unusual note to the students and researchers in attendance: “Think about the planet,” she said, “and take one less flight next year.”

Her request was no accident. It’s perfectly in line with what climate scientists are saying: one of the most impactful things we can do to limit our climate impact is fly less by plane. The 7th Heidelberg Laureate Forum (HLF), where climate science was this year’s Hot Topic, was the perfect venue to put that to the test — so I took the train there instead of flying.

A pit stop in Paris is always a nice bonus.

Why the train?

Of course, sometimes, taking the plane is simply inescapable. A simple example is traveling to places that are very far, like from Europe to the US, or from Australia to… almost anywhere. Flying is faster than any other transportation, it’s simple in these modern times, and it’s sometimes surprisingly cheap. But that being said, there are many regions where the train can be a realistically good alternative.

Mile per mile, train emissions can be up to 10 times lower than those of planes. In my particular case, coming from Birmingham, UK, to Heidelberg, would produce about 0.75 tonnes of CO2. that’s almost a ton of greenhouse gases for one single return trip (there are different ways to calculate these emissions, but this is the order on which we are on).

[By the way, here’s a calculator you can use to estimate your flying emissions]

The international average is around 4.8 tonnes of emissions per person, per year. In one blow, that’s 15% of that amount. Take 6 of these flights a year, and you’ve pretty much used up the average CO2 budget — and that’s if you live in a bubble and don’t do anything else. But this average budget is even too high. If we want to prevent catastrophic global warming, we should aim to limit our average emissions to 2.5 tonnes per year by 2030, and 0.7 tonnes by 2050.

Airplanes are one of the world’s rising CO2 emitters, and there are very few realistic ways to reduce these emissions. The first thing you can do is offset your emissions (here’s how). This is certainly worth looking into and should be considered for all plane flights. The second thing to do is to simply travel by train.

Over the same route (Birmingham – Heidelberg), the train emissions amount to 0.04 tonnes, compared to the plane’s 0.75! Needless to say, that’s a much more acceptable figure, and it’s justification enough to look for an alternative.

Train practicalities

Coffee and a good book are your best friends on long train rides.

So can you actually travel by train, is it realistic? While the UK and Germany are relatively close, they’re still over 1000 km away. Over my particular route, the distance is around 1100 km for one leg — 2200 km both ways. I changed 3 trains over this route:

– a national train from Birmingham to London;
– an international train for London to Paris;
– an international train from Paris to Mannheim;
– a local train from Mannheim to Heidelberg (which is just 20 km away).

In total, from the time I left my house to the time I arrived at the hotel, it took me 12 hours. Obviously, that’s a pretty long travel. But let’s compare it to the plane.

The plane flight itself is a mere 2 hours. But that’s not the whole issue: you also need to arrive about 2 hours earlier than your flight, during which you need to stay in line and check-in your baggage. You also need to travel from home to the airport — this usually takes anywhere between 30-60 minutes. You also need to wait around 30 minutes on arrival, to pass through border control and pick up your baggage. You then have to also take the shuttle from the airport to your arrival hotel, which in the case of Frankfurt-Heidelberg, takes around 60-90 minutes. When you add all this up, you end up with a rough estimation of 7 hours. It’s still shorter than the 12 hours by train, but certainly comparable.

A train ride from London to Heidelberg can take as little as 6 hours.

There are also other advantages to the train: it’s more comfortable and it’s easier to work or relax by watching something on a laptop or smartphone. It also feels nicer to actually see something out the window.

This isn’t to say that the train is always a solution. It’s still a long journey, and you need to plan things carefully in advance, to ensure that your connections work right. But you get some extra flexibility (you can spread your journey over 2-3 days and enjoy multiple city trips along the way), a lot of comfort, and an overall more pleasant experience.

What we can all do

The first thing to do is to be aware. We all produce greenhouse gas emissions, and emissions from planes are not trivial. Reducing the number of flights we take is one of the most impactful decisions we can make, but it’s not the only one, and it can be tackled in more than one way.

We all love what we do, and we all want to fulfill our potential and meet awesome people from all around the world. But we also need to be aware that in our quest for success, we are affecting the world in many ways, sometimes, in ways that we’re not even considering.

It’s important that we all try to play our part and build a better world for tomorrow — one step at a time.

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Andrei is a science communicator and a PhD candidate in geophysics. He is the co-founder of ZME Science, where he published over 2,000 articles. Andrei tries to blend two things he loves (science and good stories) to make the world a better place -- one article at a time.


  1. Citation: Airplanes are one of the world’s rising CO2 emitters, and there are very few realistic ways to reduce these emissions.

    there is a solution: flights must be carbon neutral in the future. Carbon neutral, for example, because the fuel was produced synthetically from CO2 and water using carbon neutral electricity.

    The car company Audi has a production line for carbon neutral fuel (citation wikipedia ( https://en.wikipedia.org/wiki/E-diesel )):
    E-diesel is a synthetic diesel fuel created by Audi for use in automobiles. Currently, e-diesel is created by an Audi research facility in partnership with a company named Sunfire. The fuel is created from carbon dioxide, water, and electricity with a process powered by renewable energy sources to create a liquid energy carrier called blue crude (in contrast to regular crude oil) which is then refined to generate e-diesel. E-diesel is considered to be a carbon-neutral fuel as it does not extract new carbon and the energy sources to drive the process are from carbon-neutral sources.

  2. Decarbonizing ships and planes
    is necessary in the long run – but it is not so easy indeed.

    The most obvious solution is synthetic fuel. The article The Thermodynamic and Economic Realities of Audi’s E Diesel ( http://euanmearns.com/the-thermodynamic-and-economic-realities-of-audis-e-diesel/ ) comes to the following conclusion regarding Audi’s synthetic diesel:

    Using European electricity prices, the energy cost of e diesel at the refinery gate would be of the order €1.8 litre – excluding manpower, capex, profit, distribution costs and taxes. Adding in the latter might easily take the price to €3 / litre, much higher than Audi’s estimate of €1 to 1.5 € per liter. This compares with a refinery gate price for FF diesel of the order €0.65 per liter. e diesel may cost 2.7 to 4.5 times as much as traditional diesel.
    The energy return on energy invested (ERoEI) for the process is at best 0.5. For every BTU of e diesel produced about 2 BTUs of electricity are consumed. E diesel is an energy sink or energy conversion where at least 50% of the energy is lost along the way.
    To convert Europe to run on e diesel would require a 12 fold increase in todays “new renewable” infrastructure and would result in a doubling of the energy consumed in the transport sector.

    Assessment: Synthetic fuel but also hydrogen as fuel is economically not a general solution for road, air and ship traffic. Whenever possible, batteries are preferable – because of their higher efficiency. But where this is not possible for capacity reasons, for example in shipping or air traffic, other solutions must be considered. Nuclear propulsion would be conceivable for shipping at some point, but only synthetic or biofuels could be considered for air traffic.

  3. “Think about the planet,” she said, “and take one less flight next year.”
    Yes, less to fly means less CO2. At some point, however, no human technical activity is allowed to emit CO2 at all. This means that eventually airplanes also have to be CO2 neutral – or that flying will simply not be possible anymore.
    1990 to 2020: Climate action results in 50% more CO2 emissions
    In the first 30 years of the climate problem, from 1990 to 2020, this was the message, the reverberation to all nations and citizens of the world: “Avoid CO2 emissions wherever you can.” The result of this call was that, in the already industrialized nations, CO2 emissions stagnated at first, and are now decreasing by about 1 percent a year. However, globally, annual greenhouse gas emissions increased from 22 to 37 gigatons, up more than 50%.

    2020 to 2050: Climate action should result in 0% more CO2 emissions
    In the next 30 years, ie until the year 2050, the highest that mankind can achieve is that the greenhouse gas emissions will not rise any further, ie in the year 2050 at most the same size as today. Even this goal can only be achieved if at least the developed countries switch to a carbon neutral economy over the next 30 years. This also means that flying must become CO2 neutral within the next 30 years.

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