Voluntary carbon offsetting is the practice of paying money to organisations that seek to reduce global greenhouse gas emissions (usually at a set price per tonne of carbon dioxide equivalent) as a way of reducing our personal climate impact. Voluntary offsets are somewhat distinct from offsets in compliance carbon schemes (such as national or regional carbon markets). The latter probably require their own discussion at some stage.
Voluntary offsetting is most commonly associated with flying, since modern jet-powered aviation is, per hour, the most climate-destructive activity open to the average citizen of the wealthy world.* I plan on posting some thoughts on the impacts and ethics of flying at some point in the future, though let me say here that I don't think that flying is an unequivocal moral evil never to be permitted under any circumstances. I do think that it represents one of the more difficult questions facing contemporary cultural assumptions and habits, not least because, unlike many other activities, few easily substituted alternatives exist.** It also represents, for those who fly more than once in a blue moon, the most obvious point at which significant carbon reductions can quickly be made.
*It may be surpassed by political careers that attempt to thwart responsible climate action, certain kinds of investment banking, or owning factories that produce extreme greenhouse gases such as HFCs, but such activities are not generally available to most people. The main contender for this title, procreation, is a special case since it involves the creation of a new agent.
Some companies or events also choose to pay for carbon offsetting in order to be able to claim that their activities are "carbon neutral" or "zero carbon". Most corporate claims to phrases such as these will be based at least partially in offsetting, since most human economic activities are associated with a carbon footprint of greater or lesser size.
There is a lot of debate around carbon offsetting, some of it around the relative merits of different kinds of offsetting and some about the ethics of offsetting at all.
The tactics of offsetting: evaluating different schemes
Let us first consider the various kinds of offsetting programmes. It is worth noting at the outset that no options are perfect (indeed, some may be only slightly better than nothing, or even worse than nothing), so it remains the case that the only real way of being carbon neutral is avoiding the carbon-intensive activity in the first place. I don't have specific company recommendations (though am happy to receive recommendations in the comments), but I will offer a few thoughts. There are three basic kinds of offsetting:
• Forestry schemes (i.e. tree-planting): The idea here is simple. Trees are made (mostly) of carbon that has been sucked out of the atmosphere, so as trees grow, they reduce atmospheric carbon concentrations. More trees means less atmospheric carbon. Well-managed forestry also has a host of other benefits, from supporting biodiversity and local employment to regulating and enhancing local rainfall. I would also include various soil management schemes here. In the past, some forestry schemes had very poor planning or oversight, meaning trees were planted in inappropriate conditions and without ongoing management and thus quickly died, representing a worse than useless investment. There is generally better accreditation today (or so I am told, though I'm not any kind of expert on offsetting accreditation), which is good, since any planting scheme needs to put appropriate species in suitable locations, rather than just plonking anything anywhere. Nonetheless, from a climate perspective, the benefits from tree planting are generally deferred for decades and are highly vulnerable to future changes. If the forest is cut down, or dries/dies out due to climate change, then the benefit is lost. So a tonne of carbon stored in a forest (or potentially stored in a forest in a few decades) is not the equivalent of a tonne of carbon left safely underground as unused fossil fuel, though it is still better than a tonne of carbon floating in the atmosphere and upper ocean. Technically, the carbon is not removed from the active carbon cycle, just placed in a slightly slower part of it.In general, I would be very hesitant about schemes offered by airlines themselves, who have a vested interest in picking projects with very low prices in order to bolster the idea that the negative impacts of air travel are small. Many airlines have a poor or mediocre track record on selecting quality offsetting schemes. If you are paying only cents or a couple of dollars per tonne of CO2e abatement, then you may well be supporting something that isn't very effective.
• Development schemes (e.g. supplying renewable energy to developing nations, or supporting energy efficiency programmes): These have many of the same benefits and drawbacks of other forms of international development. While the most popular renewable energy schemes often don't actually reduce current emissions (e.g. building a wind turbine for a settlement without electricity actually adds to short-term emissions), they do represent an investment in improving human flourishing (at least potentially, depending on many other factors) in a way that (hopefully) avoids future emissions (compared to a future in which the same development occurred with fossil fuel power). Probably the best kinds of scheme here focus on long term infrastructure investments with ongoing and self-reinforcing benefits. It is not clear to me that the developed world doesn't owe this kind of assistance to the developing world in any case, and so while voluntary support for good projects is worthwhile, I don't see that it equates in any kind of morally useful way with offsetting one's damaging activities elsewhere.
• Permit retirement: These are probably less well-known than other schemes. The idea is for the offsetting organisation to use your money to purchase emission permits in open compliance markets (like the EU carbon market) and then retire them from use, preventing their use by other polluters and so shrinking the total pool of potential carbon use in that market. Though somewhat more abstract than the other options, the benefits are immediate and measurable - as long as the scheme as a whole is working effectively, which is another very complex question for another day (see here for an accessible animated critique of carbon markets).
The strategy of offsetting: should we be doing it at all?
Second, and more importantly, lying behind questions concerning the relative pros and cons of various offsetting tactics is a more serious strategic debate about the desirability of offsetting altogether in light of its effects on moral culture. On the one hand, offsetting encourages carbon emitters to become familiar with their footprint and take some kind of financial responsibility for it. Yet on the other hand, given that all offsetting options have drawbacks sufficient to render an offset tonne not equivalent to a tonne not emitted in the first place, then the practice of offsetting represents a potential moral hazard insofar as it hides this reality by implying a climatic and moral equivalence between them.
For me, the key question is this: does supporting a culture of offsetting distract members of wealthy nations from the more important tasks of actually reducing our personal footprint and supporting responsible climate politics internationally and in our own backyard?* While I think that offsetting can do some real good and represents a retrieval ethic (trying to salvage something good out of a harmful situation), offsets come a long way down the priority list and if they become anything other than peripheral to our climate strategy then they risk becoming another distracting tokenism from the real challenges. Offsets are not necessary a token effort if people are also facing the hard questions of reducing their personal footprint and supporting responsible politics. But much of the discourse around offsets treats them as get out of gaol free cards, justifying the activity for which the offsets were sought in the first place.
*By responsible, I mean political discourse and policies that take our scientific and ethical situation seriously. This likely means radical changes to our practices (or incremental changes that work in large increments!) in order to minimise radical changes in our climate and biosphere. I know of no major parties in the Anglosphere that hold positions I would consider responsible on this matter. I don't want radical policies; I want deeply conservative policies that aim to conserve the global climate in a recognisable form for our children and grandchildren.
Some have therefore compared offsets to medieval indulgences: a price paid for a clean conscience, which often functions to justify the acts committed in the first place. If my carbon-guilt can be washed away for a small fee later (or even preemptively), then my carbon-intensive assumptions can continue unchallenged.
In sum, I think that probably the best course of action is to reduce one's own footprint as far and fast as possible, to support responsible climate politics, to support thoughtful international development, and then to "sin" boldly (in Luther's phrase) without supporting a culture of modern day indulgences. Nonetheless, I'm not totally opposed to offsetting by those who do so in good faith, via a reputable and accredited organisation. However, this should be done simply as part of one's charitable giving to worthwhile causes rather than in any attempt to assuage guilt or achieve boastful self-righteousness through "carbon neutrality".
Finally, here are some links to other discussions of carbon offsetting that I've found useful (this list may grow in future, especially if people suggest relevant links in the comments).
• Dark Optimism. Building the moral case against offsets, with cartoons.
• African land grabs and carbon offsets. Stephen Leahy outlines one of the dangers of rich countries relying too much on paying poor countries to offset their emissions.
• Cheat Neutral. A thought-provoking spoof on voluntary offsets. It is worth noting that adultery does not equate directly with carbon emissions, which are a cumulative, rather than absolute, evil.