Crossing the Baltic by ship is turning out to be spectacular, but the ship I'm on is not exactly green. 'The Festival' is not so much a ferry as a 10-decker that can double as a cruise ship. Pushing it across the Baltic seems to take several tonnes of  fuel an hour.

How to gauge the percentage of the CO₂ emissions a sole foot passenger is responsible for is tricky. The ship is carrying my body weight of course, but I need a place to sleep as well. Still, I've got no great metal machine in the hold, and I didn't ask for a casino or three bars on board either.

I pull myself from fantasies about sleek wind-powered people-carriers crossing stretches of water all over the globe to watch the gorgeous scenery - the thousands of forested islands and rocky islets that make up the Stockholm Archipelago.

The scenery, and the tax-free alcohol means the voyage is marketed as both travel and entertainment. After fond farewells in Stockholm though, and with a paper-thin budget, I'm not interested in partying. As the Scandanavian quasi-night falls, I head for my third-class cabin (with curtains, strangely, but no windows) where my Lithuanian room-mates are happy to teach me Russian, and tell of their life as labourers in Norway.

By late morning I am in mid-sized port city of Riga, with its bustling market and cute old quarter, with little time to get a ticket to Moscow. In retrospect, I should have chosen the coach, about 10£ cheaper, quicker, with less CO₂ emissions, but, as usual, the train station was easier to find, and I'm a bit of a sucker for trains -  less so when I discover they're being pulled by dirty diesel locomotives.

A highlight of the 16 hour trip, apart from the gentle, forested landscape of Latvia and Western Russia, is meeting Mihails, who explains to me some of the differences between Estonia ('more like Finland') and Lithuania and crisis-hit Latvia ('brother countries'). Before he gets off near the border, we share the following conversation:

MIHAILS: [pointing out a traditional midsummer celebration in a local paper] I think people all over Europe celebrate somethng like this

ME: Yes, I was in Sweden for Midsommar, it was very nice. Lots of Schnapps-drinking songs, and cake made from herring. But... er.. do you know the word 'hippy'?

MIHAILS: Long hair, marijuana? Listening to Beatles?

ME: Right! I think hippes are the only people who celebrate the Summer Solstice in England

MIHAILS: Ah. In England it is raining all the time, I think, and people are not feeling so good.

As the train rattles along, I make my bed in the dusk, lie down, think of herring cake in Sweden and good times in rainy old Blighty, and take comfort that even though I've been using some less-than-efficient technologies, I'm still better off than if I flew, in more ways than one.

CO₂ Emissions - Stockholm to Moscow

I'm sticking with Defra's emissions factors here, as outlined in their methodology paper.

480km passenger ferry x 112g per passenger km     = 54 kg
960km diesel train x 75g ppkm                                   = 72 kg
100km electric train x 54g ppkm                                 = 5kg
Total                                                                              =131kg

Equivalent emissions if I had flown direct:
1216km x 248g ppkm                                                   =304kg   

Note: As I move further from the UK, the emissions factors I'm using - from Defra's paper above become less strictly accurate. I'm working on the resources, while on the road, to research highly accurate emissions factors. (Anyone got any figures on the carbon intensity of electricity of different countries in Asia, and Russia in particular?) Perhaps it evens out, however - some things make the Latvian train more efficient than the UK equivalent (high occupancy, and low speed) and some less so (travelling in a sleeper carriage, using probably less efficient technology).