Who marks your carbon book?

Every quarter, carbon positions get marked. Fund NAVs go to investors. Collateral values go to credit committees. Treasury books go to auditors. Ask where the number came from and the answer is usually one of three things: a broker quote, a price feed, or the purchase price rolled quietly forward. Ask who stands behind it, and the answer is usually nobody. In any other asset class this stopped being acceptable a generation ago. In carbon it is still the norm, and the window in which it stays the norm is closing.

The mark is contested by construction

01 · Your book is not the average

Carbon is the most dispersed asset class a valuer will ever meet. The strongest credits trade at several times the weakest. The same nominal tonne is worth radically different amounts depending on rating, vintage, methodology, geography and eligibility, and each of those conditions moves on its own clock. A price feed, however good, gives you an average for something like your asset. Your book is not the average. It is a specific set of positions in specific projects in specific condition, and the distance between the feed and the book is precisely where marks go wrong.

02 · The seller's word, rolled forward

The deeper problem is provenance. A broker quote is a price at which a conflicted intermediary might transact a specific parcel. The purchase price is what you agreed to pay in a different market on a different day. The developer's update is the seller describing the asset it sold you. Rolling any of these forward and calling it a mark is the carbon equivalent of valuing an illiquid bond book at the originating dealer's price, and every finance professional knows how that story ends. The party relying on the number has to be able to get it from someone with no interest in it being high.

A price feed tells you what the market paid for something like your asset. A mark tells you what yours is worth, and someone signs it.

The rules already require better

03 · Independence is written into obligations you already have

None of this requires a new regulation, because the obligations already exist. Fund managers are required to ensure proper and independent valuation of the assets they hold. Fair value is an exit-price concept tested against what the position would actually fetch, in its actual condition, at the measurement date. Auditors are probing private-market valuation practices with increasing appetite, and listed carbon vehicles have already been through the experience of writing positions down to a fraction, in public, under audit. And for corporates, the new accounting brings the same question to the balance sheet on a statutory clock: an impairment test against fair value, every reporting date, irreversible once taken. The obligation to hold a defensible number is already in force. What has been missing is a party built to supply it.

04 · What a defensible mark looks like

The requirements assemble themselves. Independent: produced by a party that holds no title, sells no credits, transacts nothing, and is paid by the holder. Evidence-pinned: every position's mark traceable to citable evidence about that position's condition, from its eligibility status to what the satellites saw over the project last month. Continuous: the events that destroy value do not wait for quarter-end, so the record has to be alive between closes, with the mark as a live field rather than an annual reconstruction. And aggregation-correct: carbon positions fail together, so a book-level number has to respect correlation rather than average it away. Anything less is a number that survives until someone competent questions it.

The uncomfortable question

So, who marks your carbon book? If the honest answer is the seller, the broker, or a feed that has never seen your specific positions, then the book is carried at a number nobody would defend under examination, and the people it is reported to have not yet asked the question. They will. Investors are learning to ask it, credit committees are starting to ask it, and auditors are being trained to ask it. The holders who move first get to answer it on their own terms.