Abstract

The Paris Agreement commits 197 countries to achieve climate stabilisation at a global average surface temperature less than 2 °C above pre-industrial times, using nationally determined contributions (NDCs) to demonstrate progress vis-à-vis this goal. Numerous industrialised economies have targets to achieve territorial climate neutrality by 2050, primarily in the form of “net zero” greenhouse gas (GHG) emissions. However, particular uncertainty remains over the role of countries’ agriculture, forestry and land use (AFOLU) sectors for numerous reasons, inter alia: the need to balance mitigation of difficult-to-abate agricultural emissions against food security; agriculture emissions of methane do not need to be reduced to zero to achieve climate stabilisation; land use should be a large net sink globally to offset residual emissions. These issues are represented at a coarse level in integrated assessment models (IAMS) that indicate the role of AFOLU in global pathways towards climate stabilisation. However, there is an urgent need to determine appropriate AFOLU management strategies at national level within NDCs. Here, we present a new model designed to evaluate detailed AFOLU scenarios at national scale, using the example of Ireland where 34 % of national GHG emissions originate from AFOLU. GOBLIN (General Overview for a Back-casting approach of Livestock Intensification) is designed to run randomised scenarios of agricultural activities and land use combinations in 2050 within biophysical constraints (e.g. available land area, livestock productivities, fertiliser-driven grass yields and forest growth rates). Based on AFOLU emission factors used for national GHG inventory reporting, GOBLIN then calculates annual GHG emissions out to 2050 for each scenario. The long-term dynamics of forestry are represented up to 2120, so that scenarios can also be evaluated against the Paris Agreement commitment to achieve a balance between emissions and removals over the second half of this century. We outline the rationale and methodology behind the development of this biophysical model intended to provide robust evidence on the biophysical linkages across food production, GHG emissions and carbon sinks at national level. We then demonstrate how GOBLIN can be applied to evaluate different scenarios in relation to a few possible simple definitions of “climate neutrality”, discussing opportunities and limitations.

Highlights

  • Article four of the United Nations Framework Convention on Climate Change (UNFCCC)Paris Agreement (UNFCCC, 2015) states that in order for parties to achieve long-term temperature goals, peak greenhouse gas (GHG) emissions must be reached as soon as possible.Parties must strive to “achieve a balance between anthropogenic emissions by sources and removals by sinks of GHGs” (UNFCCC, 2015)

  • An important but initially unanticipated use of GOBLIN will be to explore the implications of various possible definitions of “climate neutrality”, underpinned by different value judgements. It is clear from the small selection of indicative scenarios analysed in this paper that choice of GHG aggregation metric and definition of climate neutrality profoundly alters the mix of agricultural production and land use compatible with climate neutrality in 2050 and beyond

  • The sector will play a key role in mitigation of emissions via reduced agricultural emissions intensity and increased carbon sequestration and other off-setting/displacement activities

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Summary

Introduction

Article four of the United Nations Framework Convention on Climate Change (UNFCCC). Paris Agreement (UNFCCC, 2015) states that in order for parties to achieve long-term temperature goals, peak greenhouse gas (GHG) emissions must be reached as soon as possible. There is considerable debate and uncertainty regarding the broad suite of agricultural and land use activities compatible with climate neutrality at individual country level, strongly depending on GHG aggregation metric (e.g. GWP100 or GWP*), and/or various approaches to downscale global emissions and sinks from particular scenarios compatible with climate stabilisation (Huppmann et al, 2018; Rogelj et al, 2018b), and the particular impacts of GHG mitigation on food production in different countries (Prudhomme et al, 2021) .There is an urgent need to explore implications of different definitions for national AFOLU sectors. The back-casting approach used in GOBLIN makes explicit the linkages across biophysical constraints relating model outputs (emission reduction targets) with model inputs (parameters defining production systems and land management) These explicit linkages enable GOBLIN users to better understand complementarities and trade-offs across AFOLU activities with respect to the climate neutrality objective, based on transparent and objective scenario construction. GHG reporting at Tier 1 level for soil emissions, Tier 2 level for animal emissions and Tier 3 level for forestry carbon dynamics

Modelling architectural overview
Modelling Application
Summary of module functions within GOBLIN
Scenario Generation
Cattle herd model
Grassland management module
Livestock emissions
Soil emissions
Land-use allocation
Forest emissions
Grassland Emissions
Wetland Emissions
Cropland Emissions
Forest management
Model validation
Example of Model Output
National AFOLU models for climate policy
Defining “climate neutrality”
Model limitations and development priorities
Findings
Conclusion
Code Availability
Full Text
Published version (Free)

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