Attribution of Atlantic Multidecadal Variability to External Forcing, Internal Variability and Weather Noise

Detection of externally forced climate change and attribution of the causes of the externally forced and internally generated climate variability during the last century are the central scientific issues of current climate science and the subject of important controversies. The Atlantic Multidecadal Variability (AMV) sea surface temperature is decomposed into externally forced and internally generated components using the CGCM ensemble, and the weather noise contribution to the internal component is isolated using the AGCM ensemble and interactive ensemble. The AMV has a strong contribution from the external 20th century forcing. The internal AMV variability is partially forced by the weather noise, but other sources of internal variability are also important. An important contribution to the internal AMV is associated with the internal variability of the oceanic Atlantic Meridional Overturning Circulation, and this contribution is distinct from the weather noise forced component.