Counting the (Carbon) Cost

One of the most fascinating and exasperating aspects of trying to take this trip in a 'green' way is how difficult it is to guage the environmental impact of different modes of travel. Chief among these are the wildly different values that different sources offer for things like the CO2e per passenger kilometer of travel for various modes and routes.

Rarely are these aggregate values accompanied by vital context about their methodology, source or currency. For example, railways across Europe have undergone substantial electrification in recent years, so data from even a few years ago may be misleadingly high. Airlines have decarbonise to a lesser degree, but the lack of consensus over the potency of 'radiative forcing' seems to be behind most of the variety in CO2e figures for air travel.

Simple comparisons between modes are in any case not so simple. The international ICE train that I took from Brussels to Cologne claims to produce less than 1g of CO2e per passenger Km; the diesel hauled Nordland line with its 80s vintage locomotives may emit over 100g CO2e/passenger-Km - close to value for short haul flying (there are no published data for the specific route, but that is towards the high end for similar trains). Do these differences between lines even matter? As Dr Beeching infamously failed to grasp railways function as networks: cherry picking just the greenest routes may not be reasonable since they must be fed passengers from less efficient local and regional trains. Unsatisfyingly, there are wide variations in estimates for the 'average' train journey, and operators each claiming to use 100% green electricity to power their trains have large, counter intuitive differences in their emissions figures.

Estimates for RoPas ferries are even wider with nearly 300g separating the highest and lowest I found (the high, frequently cited estimate appears to originate with a carparking company - I'm unsure why they have an opinion on the matter and think EU data are probably more reliable). CO2e per passenger-Km data are in any case harder to come by for shipping, which tends to work in tonnes shipped (as ships mostly move things rather than people). CO2e itself has significant challenges, since it struggles to meaningfully reflect the differing persistence of various greenhouse gases or things like radiative forcing.

All in all, I am frustrated at the quality of consumer information on this point - every operator who provided a figure gave insufficient context (what scope of emissions, what methodology etc); many - DFDS especially - gave vague intentions about becoming green. Authorities, like various European Union bodies, were equally poor at contextualising their figures. On balance of probability, this trip is likely significantly greener than four flights; I am left with an uncomfortable element of doubt as the available data indicate my investment of extra travel time and treasure falls on a continuum from having prevented about a half a tonne of CO2e emissions on the one hand, to being slightly worse than just flying on the other. I have at least chosen modes and routes that have a path to almost complete decarbonisation - the move to battery locos on the Nordland line is already planned and new propulsion for the ferries is plausible in the near term.

Environmentalism is hard.En savoir plus