GOBLIN : A land-balance model to identify national agriculture and land-use pathways to 1 climate neutrality via backcasting 2

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Introduction
. The grassland module (3) computes the energy (feed) requirements 231 of each animal cohort within the national herd, fertiliser application and subsequently the area 232 of grassland needed (depending on concentrate feed inputs, fertiliser application rates and grass 233 utilisation rate) and the grassland area free for other purposes ("spared grassland"). Emissions   (

Model validation 533
The main purpose of the GOBLIN model is to provide an evidence base for climate action in 534 Ireland's AFOLU sector, aligned with existing GHG accounting procedures that will ultimately 535 be used (with refinements through time) by policy to track progress towards climate neutrality.

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Acknowledging the significant scientific uncertainty around many AFOLU fluxes, the most 537 appropriate manner to validate GOBLIN in relation to its core purpose, is to test how well it 538 replicates NIR fluxes from the same activity data. Largely, these activity data are inputted to 539 GOBLIN in the same format as for the NIR, with some differences relating to the simulation  To assess whether or not GOBLIN has achieved its goals, validation of emission and removal  Beginning with land-use and land-use change (Fig. 7), solid lines represent CO2, CH4 and N2O

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To demonstrate and explore the critical functions of GOBLIN, several scenarios were analysed 592 to reflect national level GHG reductions within the AFOLU sector (Table 5). As set out in 593 Ireland's Climate Action Bill (2021), Ireland must achieve a 51% emission reduction by 2030.

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Given that agriculture makes a significant contribution to the national emissions profile  • 100% of organic soil under grassland rewetted • Remaining area assumed to be mineral and afforested.
• Remaining organic area taken out of production 26086 4 Animal reduction and increased production • Dairy, Beef and sheep herd numbers reduced by 10%, 50% and 50% by 2050, respectively.
• Milk output increased by 14% per cow • Beef live weight + 20% 0 5 Animal reduction, increased production, afforestation and wetlands • Dairy, Beef and sheep herd numbers reduced by 10%, 50% and 50% by 2050, respectively • Milk output increased by 14% per cow • Beef live weight + 20% • 100% of organic soil under grassland rewetted • Remaining area assumed to be mineral and afforested.
• Remaining organic area taken out of production 24299 605 Fig. 9 and 10 present the main AFOLU GHG fluxes. Firstly, the agricultural emissions ( Fig. 9) 606 illustrate the results for CH4 emissions from enteric fermentation and manure management,

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N2O results from manure management and other direct and indirect N2O emission pathways, 608 and finally, CO2 emissions from fertiliser application to soils. Emissions related to livestock 609 are slightly higher in scenarios that have increased production related to milk and beef output 610 than scenarios with default production estimates.  where rewetting has taken place. Regarding forestry, Fig. 10 highlights the expected value in 638 2050, drawing a line linearly from 2015 to 2050. As expected, sequestration potential is greater 639 at higher levels of afforestation. The entire time series is explored in more detail in Fig. 10.

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Wetland emissions increase, relative to scenario 0, by 4 and 5% in scenarios in which rewetting 641 takes place. Lastly, we have assumed no emissions changes for cropland.

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To further elaborate the forestry modelling, Fig. 11 shows the forest sequestration time series    preparation. 865 Prudhomme, R conducted design, development, analysis and validation. 866 Duffy, B conducted design and development. 867 Gibbons J conducted validation, review and editing.

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Ryan, M conducted validation, review and editing.

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Style, D conducted design, development, analysis, review and editing.

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The authors declare that they have no conflict of interest.