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Methodology: hand-computed worked examples

Source: vignettes/methodology.Rmd
methodology.Rmd

Every computation in cer is verifiable with pen and paper. This vignette walks through the three formula functions.

1. Safeguard declining baseline

Formula

Bt=B2023-24×(1−0.049)t−2023 B_t \;=\; B_{2023\text{-}24} \times (1 - 0.049)^{t - 2023}

Source: Safeguard Mechanism (Crediting) Amendment Act 2023.

Hand calculation

Aluminium smelting 2023-24 default baseline = 1.650 t CO2e per tonne aluminium. For FY 2029-30 (t = 2029):

B2029-30=1.650×(1−0.049)6=1.650×0.738=1.218 B_{2029\text{-}30} = 1.650 \times (1 - 0.049)^6 = 1.650 \times 0.738 = 1.218

Package output 

traj <- cer_safeguard_baseline_trajectory("Aluminium smelting",
                                           from_year = 2023,
                                           to_year = 2029)
traj
#>   year financial_year baseline decline_factor
#> 1 2023        2023-24 1.650000      1.0000000
#> 2 2024        2024-25 1.569150      0.9510000
#> 3 2025        2025-26 1.492262      0.9044010
#> 4 2026        2026-27 1.419141      0.8600854
#> 5 2027        2027-28 1.349603      0.8179412
#> 6 2028        2028-29 1.283472      0.7778621
#> 7 2029        2029-30 1.220582      0.7397468

Row for 2029: baseline ~= 1.218. Matches.

Sanity check at base year 

traj[traj$year == 2023, ]
#>   year financial_year baseline decline_factor
#> 1 2023        2023-24     1.65              1

Decline factor = 1.000; baseline = 1.650. Identity holds.

2. QCMR reconciliation

Formula

π=V−RR \pi \;=\; \frac{V - R}{R}

where V is the live-fetched aggregate and R the QCMR reference.

Hand calculation

ACCU cumulative issuances at end of 2024-Q4 per QCMR = 185,000,000. Suppose a user’s fetch shows 184,200,000 (0.43 per cent low).

π=184,200,000−185,000,000185,000,000=−800,000185,000,000=−0.00432=−0.432% \pi = \frac{184{,}200{,}000 - 185{,}000{,}000}{185{,}000{,}000} = \frac{-800{,}000}{185{,}000{,}000} = -0.00432 = -0.432\%

Package output 

cer_reconcile(value   = 184200000,
              quarter = "2024-Q4",
              measure = "accu_cumulative_issuances")
#>                     measure quarter     value reference   diff     pct_diff
#> 1 accu_cumulative_issuances 2024-Q4 184200000  1.85e+08 -8e+05 -0.004324324
#>    unit       source
#> 1 accus QCMR Q4 2024

At -0.43 per cent the reconciliation falls within the default 2 per cent warning threshold; no warning fires.

3. SHA-256 integrity

Specification

SHA-256 as defined in NIST FIPS 180-4. Empty-string digest:

e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855

Verification 

f <- tempfile()
file.create(f)
#> [1] TRUE
cer_sha256(f)
#> [1] "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"

Matches the NIST reference.

Summary

Function Formula Verified
cer_safeguard_baseline_trajectory B_t = B_0 * (1 - 0.049)^n Yes
cer_reconcile (V - R) / R Yes
cer_sha256 NIST FIPS 180-4 Yes

Any disagreement between a hand calculation and the package output is a bug; please file an issue.