You'd be surprised. Long trips literally produce tons.

The emissions of this trip, if every passenger flew economy, is >2 ton CO2 per person.

The annual emission of a eu citizen is 4 to 7 ton a year so for a month that's 350kg, given that he is not living on eu standards it's quite safe to take the lower bound. The co2 of hitching on cargo ships and trucks is neglectabel, but if he has to catch a bus for most land travel, we can set it to 500kg max.

Taking the plane emissions at the minimum bound and the alternative maximal, it's still 3x less. And personal emissions I think we could reduce by a lot in the next 10 years with greener agriculture, industry and just consuming less. Plane travel will not improve drastically the coming 20 years

Presumably you'd need to compare that to his regular consumption for those 35 days, so marginally, it might really only be the water purification and a little extra weight of food.

It would kinda be interesting to see a detailed breakdown of the comparison.

A person eats and drinks every day, regardless of being on a journey, or stationary. If he sourced locally along the trip, there's a good chance his emissions were lower, since Germany has higher per capita emissions than most countries, roughly estimated.

But even if he brought all the supplies from Germany, that would only increase transportation emissions slightly. Emissions for the goods themselves remained equal, wether they are consumed at home or elsewhere.

I think it's mainly two reasons: Consciousness, and trying to make the world a better place.

People similarly refuse to participate in other things which are done anyways. Think about veggies, Nestle, refusing to work in certain industries or for certain employers, reddit blackout, fair trade products.

People abstain from what they deem wrong to have no part in it. And to use the power they have to not support what they deem wrong, maybe even shed light on it and inspire others.

When enough people do the same, it absolutely can have real world consequences. Change has to start somewhere.

I also refuse to fly, but my commute isn't 16000km either.

That may be true for one particular flight but if all the people who fly only because "the plane is going anyway" stopped, I'm sure that would partially empty those planes enough that airlines would consider reducing the flights' frequency. But if anyone knows studies/arguments implying the opposite, I'd be very interested to hear them.

TIL planes fly empty if no one buys a ticket