ghg-inventory-1990-2013

Table 1.5.4
Key categories under the Kyoto Protocol and corresponding categories under the
Climate Change Convention
Category as reported under the Climate Change
Convention
Conversion to Forest Land
Conversion to Grassland
Forest Land Remaining Forest Land
Article 3.3 and 3.4 activities under the Kyoto
Protocol
Afforestation and reforestation
Deforestation
Forest Management
1.6 Inventory uncertainty
1.6.1 Reporting under the Climate Change Convention
Uncertainty estimates are an essential element of a complete greenhouse gas emissions
and removals Inventory. The purpose of uncertainty information is not to dispute the
validity of the Inventory estimates but to help prioritise efforts to improve the accuracy of
inventories and guide decisions on methodological choice (IPCC, 2006d). Inventories
prepared in accordance with IPCC guidelines (IPCC, 2006d) will typically contain a wide
range of emission estimates, varying from carefully measured and demonstrably complete
data on emissions to order-of-magnitude estimates of highly variable emissions such as
N 2 O fluxes from soils and waterways.
In this Inventory submission, New Zealand included a Tier 1 uncertainty analysis of the
aggregated figures as required by the Climate Change Convention Inventory guidelines
(UNFCCC, 2013) and IPCC good practice guidance (IPCC, 2006d). Uncertainties in the
categories are combined to provide uncertainty estimates for the entire Inventory for the
latest Inventory year and the uncertainty in the overall Inventory trend over time. LULUCF
categories have been included using the absolute value of any removals of CO 2
(table A2.1.1). Table A2.1.2 calculates the uncertainty in emissions only (ie, excluding
LULUCF removals).
In most instances, the uncertainty values are determined by analysis of emission factors
or activity data using expert judgement from sectoral or industry experts, or by referring
to uncertainty ranges provided in the IPCC guidelines. The uncertainty for CH 4 emissions
from enteric fermentation was calculated by expressing the coefficient of variation
according to the standard error of the methane yield. A Monte Carlo simulation has been
used to determine uncertainty for N 2 O from agricultural soils. For the 2013 data, the
uncertainty in the annual estimate was calculated using the 95 per cent confidence
interval determined from the Monte Carlo simulation as a percentage of the mean value.
Total emissions
Uncertainty in 2013
The uncertainty in total emissions (excluding emissions and removals from the
LULUCF sector) is 13.1 per cent. This is a decrease of ± 0.2 per cent from 2012.
Emissions of N 2 O from agricultural soils (section 6.5), CH 4 from enteric fermentation and
CH 4 from solid waste disposal contribute the highest levels of uncertainty. These
categories accounted for ± 7.7 per cent, ± 5.6 per cent and ± 8.6 per cent, respectively, of
New Zealand’s total emissions uncertainty in 2013. The uncertainty in these categories
reflects the inherent variability when estimating emissions from natural systems.
Uncertainty in the trend
The trend uncertainty in total emissions (excluding emissions and removals from the
LULUCF sector) from 1990 to 2013 is ± 14.6 per cent. This is an increase of ± 3.5 per
New Zealand’s Greenhouse Gas Inventory 1990–2013 21