Achieving ambitious climate change mitigation necessitates integrated approaches across energy, agriculture, land use, and forestry (AFOLU) systems. Yet, national modelling typically treats these sectors in isolation and focuses on emissions rather than climate impacts. This paper introduces TIM-LEAF, a national integrated modelling framework for Ireland that harmonises energy, agriculture and forestry systems within a consistent modelling structure, combining cost-optimisation of the energy system with simulation of AFOLU dynamics and temperature response.</p> <p>TIM-LEAF extends the TIMES-Ireland Model, a well-established national energy systems model, by explicitly incorporating land resource allocation, agricultural production, forestry dynamics, and inventory-aligned greenhouse gas accounting for carbon dioxide, methane and nitrous oxide across energy and AFOLU sectors. Land is treated as a finite resource, endogenously allocated to competing uses like bioenergy crops and forestry—subject to capacity constraints and exogenous conversion rates between land types. </p> <p>Agricultural production levels are based on national projections, and the remaining land is allocated endogenously between energy crops and forestry within the optimisation framework. A detailed forest module captures growth, carbon sequestration, and biomass supply chains, accounting for carbon saturation effects. This enables analysis of interactions between agricultural production, forest carbon sinks, bioenergy supply and energy system transformation under national carbon budgets.</p> <p>TIM-LEAF is coupled to the FaIR v2.1.3 simple climate model, enabling the evaluation of multi-gas mitigation impacts on national temperature and the role of individual gases, particularly methane, in shaping peak warming and overshoot dynamics. This paper thus demonstrates the capabilities of TIM-LEAF and sectoral dynamics in high level scenarios. </p> <p>The paper makes four contributions: it presents Ireland's first inventory-aligned national model for these interconnected systems; introduces forest carbon dynamics within a TIMES-based optimisation model; demonstrates a method for coupling national multi-gas emissions pathways to a simple climate model to quantify temperature responses; and offers a transferable methodological template for national-scale energy-land system integration.