Reforestation scenarios shape global and regional temperature outcomes

Abstract Large-scale reforestation is a prominent proposed climate mitigation strategy, but its full temperature impact remains poorly understood. Here, we present the first comparison of temperature responses to three distinct reforestation potentials using a fully-coupled Earth System Model. We find that reforestation consistently provides net global cooling, ranging from -0.13°C to -0.25°C, due to carbon uptake partially offset by biogeophysical warming. Crucially, a comparable net global cooling can be achieved with substantially smaller (450 Mha less area) but strategically located reforestation. Reforestation locally cools the tropics but causes albedo-driven warming in higher latitudes, which is often amplified by non-local effects. The largest differences between scenarios arise from these non-local effects, showing that planting locations shape the biogeophysical response through atmospheric feedbacks. Our findings underscore the benefits of "climate-smart" policies that focus on the geographical placement of reforestation, considering both biogeochemical and local biogeophysical effects to maximize cooling benefits.