资源环境科技发展态势分析平台

Global energy budget constraints(1-3) suggest an equilibrium climate sensitivity around 2 degrees C, which is lower than estimates from palaeoclimate reconstructions(4), process-based observational analyses(5-7), and global climate model simulations(8,9). A key assumption is that the climate sensitivity inferred today also applies to the distant future. Yet, global climate models robustly show that feedbacks vary over time, with a strong tendency for climate sensitivity to increase as equilibrium is approached(9-18). Here I consider the implications of inconstant climate feedbacks for energy budget constraints on climate sensitivity. I find that the long-term value of climate sensitivity is, on average, 26% above that inferred during transient warming within global climate models, with a larger discrepancy when climate sensitivity is high. Moreover, model values of climate sensitivity inferred during transient warming are found to be consistent with energy budget observations(1-3), indicating that the models are not overly sensitive. Using model-based estimates of how climate feedbacks will change in the future, in conjunction with recent energy budget constraints(1,19), produces a current best estimate of equilibrium climate sensitivity of 2.9 degrees C (1.7-7.1 degrees C, 90% confidence). These findings suggest that climate sensitivity estimated from global energy budget constraints is in agreement with values derived from other methods and simulated by global climate models.