▶ Internal atmospheric variability, also termed “climate noise” , arises from non-linear dynamical processes intrinsic to the atmosphere(Madden, 1976; Schneider and Kinter,1994; Feldstein, 2000; Deser et al., 2010).
▶ Internal variability is the natural variability of the climate system that occurs in the absence of external forcing (Deser et al., 2010). Although the atmosphere contains little memory beyond a few weeks, it exhibits long-time scale variability characteristic of a random stochastic process. Internal climate variability arises from atmospheric, oceanic, land, and cryospheric processes and their coupled interactions(Kay et al., 2014).
▶ Uncertainty in future climate change derives from three main sources: forcing, model response, and internal variability (e.g., Hawkins and Sutton 2009; Tebaldi and Knutti 2007).
▶ All 30 CESM-LE members use the same model and the same external forcing. Each CESM-LE ensemble member has a unique climate trajectory due to small round-off level differences in their atmospheric initial conditions. (Kay et al., 2014).
Spread of Ensembles
▶ Standard deviation of the absolute values of differences between ensemble mean and 30 members. Simply put, the CESM-LE ensemble spread results from internally generated climate variability alone. Standard deviation of the absolute values of differences between ensemble mean and 30 members. Simply put, the CESM-LE ensemble spread results from internally generated climate variability alone.
