I recently flew to Florida to visit family. My round-trip economy seat emitted roughly two tonnes of carbon dioxide, according to one carbon offsetting website. By contrast, the average person in Britain is responsible for roughly seven tonnes for the entire year, already quite high by global standards.

This makes me a climate change villain. Dumping such huge amounts of carbon into the atmosphere seems clearly morally wrong, because of the harm this will cause others. But carbon offsets let me fly with a clear conscience – for now.

When I buy an offset, carbon emissions are reduced elsewhere, cancelling out those from my flight. It might involve planting or preserving trees, or installing cheap and efficient stoves. Offsetting my Florida trip cost £13 – a couple of drinks in the departures lounge.

Convenient. But perhaps too easy? Offsetting clearly raises the scientific question of whether a purchase will really reduce global carbon emissions. This is difficult and controversial stuff, better suited to climate scientists and economists.

Philosophers, by contrast, deal in hypotheticals. So let’s assume that offsetting “works” and it cancels out my flight emissions. Does that make the flight morally OK?

Offsetting and consequentialism

Many people remain suspicious. The writer and environmentalist George Monbiot famously compared carbon offsetting to the sale of medieval Catholic indulgences, where the rich could buy themselves out of sin. Monbiot writes that from sellers of offsets, “you can now buy complacency, political apathy and self-satisfaction”.

But I think he is wrong. In moral philosophy, so-called “consequentialist” theories say that when it comes to the rightness or wrongness of some action, the consequences are all that matter. If any ethical theory vindicates offsetting, it is this.

Consequentialism has problems as a general moral theory. For example, it might license horribly unjust actions now, such as killing one innocent person because their organs will save the lives of five seriously ill people. Consequentialism cares only about the “total”, which seems wrong in the case of human lives: five saved lives don’t normally outweigh one murder.

Those who benefit from the offset might not be the same people harmed by the flight, but when it comes to climate, we should care (at least a bit) about the total amount of carbon in the air. So a focus on total emissions does seem at least partly correct about the environment.

How much do we care, and does that matter?

Another ethical worry is that offsets are only cheap because few people buy them.

For instance, one cheap method of offsetting is to replace inefficient stoves in the developing world. This saves lots of carbon for little money. However these savings can’t go on forever, and when eventually the last stove is replaced, the schemes will get more expensive. In the philosophical jargon, cheap offsetting depends on “partial compliance”. But this is not always a problem: it’s not a moral problem for voting that if everybody voted, the queue at the polling station would be longer.

Rising prices lead to a second worry. As philosopher Kai Spiekermann has noted, the robustness of the motivation to offset is a little dubious. Maybe I’ll pay the £13 now, but what about £200? What if I can’t afford that – will I really give up flying altogether?

I’m not sure. But I think this problem is irrelevant to my Florida flights. If offset prices go up, and in a decade I fly without offsetting, then that will be morally wrong. Perhaps it will also show that my motivation this year wasn’t very robust.

But it won’t show that this year’s flight-and-offset package was wrong. By analogy: suppose that you stop giving to charity when the economy crashes. This might show that your donations during the good times were not backed by very robust moral motivation – you only helped when it didn’t sting too much. That’s not great. But it doesn’t mean that your donations during the good times were morally wrong.

Offset upset

Wouldn’t it be better if we all give up flying because of climate change, rather than fly and offset? Even defenders of offsetting often say this. But flying brings real benefits, even if only to a fraction of humanity. If we can get those benefits without harming the environment, then that’s a good consequence, which counts for something morally.

Even thinking about offsetting can be beneficial. Spend some time with a carbon offset calculator, and you will likely face some uncomfortable truths.

Rich people (in global terms) like travel, and one such truth is that there’s no carbon-friendly way to cross the ocean. Last year, my family took the boat from Southampton to New York for a close friend’s wedding, partly for climate reasons, and partly to avoid a flight with a toddler. We were dismayed to learn that the cruise ship was probably worse for the environment than flying would have been.

As with tipping in American restaurants, a good slogan might be: “If you can’t afford the offset, then you can’t afford the flight.” But many people who oppose tipping on moral grounds don’t stop dining out. They just stop tipping, which is the worst of both worlds.

Don’t be like that. So assuming, as I have been, that offsetting does work, stop worrying about the climate impacts of flying, if you can afford to offset – and actually do so.