Decadal to multidecadal variability and the climate change background

Abstract

[1] Three prominent quasi-global patterns of variability and change are observed using the Met Office's sea surface temperature (SST) analysis and almost independent night marine air temperature analysis. The first is a global warming signal that is very highly correlated with global mean SST. The second is a decadal to multidecadal fluctuation with some geographical similarity to the El Niño-Southern Oscillation (ENSO). It is associated with the Pacific Decadal Oscillation (PDO), and its Pacific-wide manifestation has been termed the Interdecadal Pacific Oscillation (IPO). We present model investigations of the relationship between the IPO and ENSO. The third mode is an interhemispheric variation on multidecadal timescales which, in view of climate model experiments, is likely to be at least partly due to natural variations in the thermohaline circulation. Observed climatic impacts of this mode also appear in model simulations. Smaller-scale, regional atmospheric phenomena also affect climate on decadal to interdecadal timescales. We concentrate on one such mode, the winter North Atlantic Oscillation (NAO). This shows strong decadal to interdecadal variability and a correspondingly strong influence on surface climate variability which is largely additional to the effects of recent regional anthropogenic climate change. The winter NAO is likely influenced by both SST forcing and stratospheric variability. A full understanding of decadal changes in the NAO and European winter climate may require a detailed representation of the stratosphere that is hitherto missing in the major climate models used to study climate change.

Twentieth century bipolar seesaw of the Arctic and Antarctic surface air temperatures

“…Although Mann and Emanuel [2006] suggested that the origin of the AMO may be anthropogenic, and indeed recent fluctuations of the AMO are likely to have a near in phase anthropogenic component , a long-term ice core d 18 O data from the south-central Greenland [Stuiver et al, 1995] indicates that similar quasi-periodic oscillations have existed for hundreds of years before the age of industrialization. This is supported by an analysis of proxy and instrumental climate data for the last 330 years showing a near 70 year fluctuation of surface temperature consistent in phase with AMO time series of Parker et al [2007] in the Atlantic region of the Northern Hemisphere [Delworth and Mann, 2000].…”

“…[12] The AMO index based on an eigenvector analysis of worldwide sea surface temperature [Parker et al, 2007] is shown in Figure 2b, together with its 17 year running average. Note that the Parker et al AMO time series is quite similar to that of Trenberth and Shea [2006] even though the calculation details are different.…”

Zonally asymmetric trends of winter total column ozone in the northern middle latitudes

“…4d) is responsible for the weakening of the Aleutian Low (Wendler et al 2014) and leads to positive correlations between TCO anomalies and SSTs over the eastern tropical and extratropical Pacific Ocean. There are also high correlations between North Pacific TCO and SST variations over the Indian Ocean and South Pacific Ocean, which may be related to the non-local effects of the Inter-decadal Pacific Oscillation (IPO) (Parker et al 2007;Dong and Dai 2015). By contrast, the correlations (not shown) between zonal TCO anomalies averaged over northwestern North America and SSTs are of opposite sign to the correlations of zonal TCO anomalies over the North Pacific, suggesting that the SST changes have a significant contribution to the positive TCO trends over northwestern North America (Fig.…”

Assessment of Rainfall Variability and Its Relationship to ENSO in a Sub-Andean Watershed in Central Bolivia

“…This indicates a delayed response of the precipitation anomaly to the SOI anomaly. Parker, et al [45] noted that ENSO might have lagged signatures in some tropical processes in the off-equatorial ocean, hence it might affect the frequency of El Niño and La Niña events. Therefore, a phase shift in the study area might happen due to some delayed processes elsewhere.…”

“…This was done by estimating an average SOI value for each hydrological year (i.e., from September to August) of the study area, followed by applying thresholds of +8 and −8 in the SOI scale to identify strong events of El Niño and La Niña, respectively [42]. ENSO effects on the climate in South America were analyzed in other studies [43,44], where a decadal to multi-decadal variability in the frequency and type of ENSO events was observed [43,45]. For example, Meinke, et al [46] recognized that ENSO variability is well defined within the standard period of 2.5 to 8 years; however, decadal (9 to 13 years) and interdecadal (15 to 18 years) periods are also significant for explaining ENSO variability.…”