Inquiry into the climate response to external forcing perturbations has been the central interest of climate dynamics. But the understanding of two important aspects of climate change response—nonlinearity and regionality—is still lacking. Here a Green’s function approach is developed to estimate the linear response functions (LRFs) for both the linear and quadratic nonlinear response to ocean thermal forcing in a climate model, whereby the most excitable temperature modes, aka the neutral modes, can be identified for the current Earth climate. The resultant leading mode of the nonlinear response is characterized by a polar-amplified global cooling pattern, unveiling an intrinsic inclination of the modern climate towards cooling. Moreover, optimal forcing patterns are identified to most efficiently excite the corresponding neutral mode patterns. The forcing-response framework developed herein can be utilized to determine the optimal forcing patterns to inform solar geoengineering experiments and to interpret regional climate response and feedback in general.

询问气候对外部强迫扰动的反应一直是气候动力学的主要兴趣。但是，仍然缺乏对气候变化应对的两个重要方面（非线性和区域性）的理解。这里开发了格林函数方法，以估计气候模型中对海洋热强迫的线性和二次非线性响应的线性响应函数（LRF），从而可以确定最易激发的温度模式，也就是中性模式。当前的地球气候。非线性响应的最终领先模式的特征是极地放大的全球冷却模式，揭示了现代气候向冷却的内在倾向。此外，确定最佳强制模式以最有效地激发相应的空档模式。