Methane (CH₄) is a strong greenhouse gas that can accelerate climate change and offset mitigation efforts. A key assumption embedded in many large-scale climate models is that ecosystem CH₄ emissions can be estimated by fixed temperature relations. Here, we demonstrate that CH₄ emissions cannot be parameterized by emergent temperature response alone due to variability driven by microbial and abiotic interactions. We also provide mechanistic understanding for observed CH₄ emission hysteresis.