Carbon offsets: what buying a tonne of forgiveness actually gets you

The proposition sounds clean: a flight emits a tonne of carbon dioxide, somebody somewhere prevents or removes a tonne, money connects the two, and the atmosphere breaks even. For a decade this logic padded corporate net-zero claims and airline checkout pages. Then journalists and academics audited the tonnes, and the market has been reckoning with the results ever since.

For an offset to mean anything, three conditions must hold. The reduction must be additional, meaning it happened because of the credit money and not otherwise. It must be permanent on something like the timescale of the CO2 it excuses, which lingers for centuries. And its baseline, the story of what would have happened without the project, must be honest. Each condition invites optimism, and optimism was, for years, the product.

The starkest findings concerned avoided deforestation, the largest category, in which credits are issued for forest that would supposedly have been cleared. Analyses published from 2023 onward, examining projects behind credits used by household-name brands, concluded that the great majority of examined credits represented no real emission reduction: the threatened clearance in the baselines had been overstated, sometimes dramatically. Forest that did receive protection could still burn or be logged later, converting permanent claims into temporary ones. Renewable-energy credits suffered a quieter failure, as wind and solar became profitable without subsidy, making credits for building them non-additional almost by definition. Prices told the same story from inside: a market selling genuine atmospheric repair for a few dollars a tonne was describing something other than repair.

What survives the audit

The response has split the market into layers with honest labels. At the top sits durable carbon removal, direct air capture, mineralisation, bio-oil injection and kin, where a tonne is physically taken out and stored on geological timescales. It is verifiable and currently expensive, which is roughly the sign the physics predicts. Nature-based projects continue, with tightened methodologies and a growing preference for framing them as contributions to conservation rather than licences against specific emissions. Standards bodies and advertising regulators, meanwhile, have moved against carbon-neutral claims built on cheap credits, and several jurisdictions now police them as potential greenwashing.

For a company or a household, the resulting guidance is unglamorous. Reductions come first, since a tonne never emitted needs no forgiveness. Money spent on climate beyond that does most good either buying durable removal, priced accordingly, or funding conservation and clean development stated as what it is, a contribution, not an offset. The market's decade of cheap absolution was, in the main, exactly as priced.