On Generalized Langevin Dynamics and the Modelling of Global Mean Temperature

Since Hasselmann and Leith, stochastic Energy Balance Models (EBMs) have allowed treatment of climate fluctuations, and at least the possibility of fluctuation-dissipation relations.   However, it has recently been argued that observations motivate heavy-tailed temporal response functions in global mean temperature. Our complementary approach  (arXiv:2007.06464v2[cond-mat.stat-mech]) exploits the correspondence  between Hasselmann’s EBM and  Langevin’s equation (1908).  We propose mapping the Mori-Kubo Generalised Langevin Equation (GLE) to generalise the Hasselmann EBM. If present, long range memory then simplifies the GLE to a fractional Langevin equation (FLE).  We describe the EBMs that correspond to the GLE and FLE,  and relate them to  Lovejoy et al’s FEBE [NPG Discussions, 2019; QJRMS, to appear, 2021].