Observed climate variations consist of forced and free components. The former is forced by variations of greenhouse gas (GHG), aerosol concentrations, or solar constant, and the latter arises internally either from the chaotic dynamics of individual climate system components or owing to coupled climate processes. For small incremental changes in the climate system, the two components can be further divided into thermodynamically induced and dynamically induced as listed in the matrix (adapted from Mike Wallace's presentation at the National Taiwan University Climate Change Conference). Abbreviations: COWL, cold ocean–warm land pattern; NAO, North Atlantic Oscillation; PNA, Pacific–North American pattern; QBO: quasi-biennial oscillation; TAV, tropical Atlantic variability; PDO, Pacific decadal oscillation.
Citation: Bulletin of the American Meteorological Society 95, 2; 10.1175/BAMS-D-13-00015.1