# How does sampling uncertainty cut tree carbon credits in a CCTS afforestation project?

Canonical: https://senseible.earth/answers/ccts-afforestation-tree-carbon-uncertainty-discount

Tool BM-T-AR-0004 measures uncertainty as the standard error expanded to 90% confidence, divided by the mean. Up to 10% there is no discount. Above that, project tree carbon is cut by 25%, 50%, 75% or 100% of the uncertainty, in bands up to and beyond 30%.

## How uncertainty is measured

Take the standard error of the mean, multiply it by the t value for 90% confidence, and divide by the mean. The tool's own example: a mean of 45.328 t dry matter per ha from 34 plots with a standard deviation of 12.776 gives a standard error of 2.191, expanded to 3.707, an uncertainty of 8.18%. Only sampling uncertainty is counted.

## Discount bands

- Up to 10%: no discount.
- Over 10% to 15%: 25% of the uncertainty.
- Over 15% to 20%: 50%.
- Over 20% to 30%: 75%.
- Over 30%: 100%.

## Which way it cuts

The discount lowers project estimates and raises baseline estimates, so both sides move against you. The tool's example: 60 plus or minus 9 t dry matter per ha is 15% uncertainty, a discount of 25% x 9 = 2.25, so the project mean becomes 57.75 and a baseline mean would become 62.25.

## Ways to keep it low

- Lay enough plots and stratify by species, age and site so each stratum is uniform.
- Baseline tree and shrub change may be taken as zero on visibly degraded land, such as eroded, saline or mine spoil land, with documents or participatory rural appraisal.
- Shrub strata with crown cover under 5% count as zero shrub biomass. Defaults: carbon fraction 0.47, root-shoot ratio 0.40 for shrubs.

## What Senseible does here

Senseible gives carbon credit eligibility signals from your records; it does not register projects or issue credits. It keeps dated, fingerprinted fuel and electricity invoices that a project's monitoring records can draw on.

- [Afforestation CCTS credits](https://senseible.earth/answers/bm-fr05-002-afforestation-ccts-credits)
- [Dead wood and litter defaults](https://senseible.earth/answers/ccts-afforestation-dead-wood-litter-defaults)
- [Soil carbon in afforestation](https://senseible.earth/answers/ccts-afforestation-soil-carbon-tool)

Sources: [BEE, BM-T-AR-0004 Estimation of carbon stocks and change in carbon stocks of trees and shrubs in A/R ICM project activities (CCTS Offset Mechanism, version 1.0, 27 March 2025): Appendix 2](https://beeindia.gov.in/WriteReadData/RTF1984/RTF-PDF-cbeb6b67d811aec8_1776061824.pdf), [BEE, Methodologies and Tools under the CCTS Offset Mechanism](https://beeindia.gov.in/view_content.php?lid=571&lang=1)

Last reviewed 2026-10-25.