A unified proxy for ENSO and PDO variability since 1650

Abstract

Abstract. In this manuscript we have attempted to consolidate the common signal in previously defined proxy reconstructions of the El Niño-Southern Oscillation into one individual proxy titled the Unified ENSO Proxy (UEP). While correlating well with the majority of input reconstructions, the UEP provides better representation of observed indices of ENSO, discrete ENSO events and documented historical chronologies of ENSO than any of these input ENSO reconstructions. Further to this, the UEP also provides a means to reconstruct the PDO/IPO multi-decadal variability of the Pacific Ocean as the low-pass filtered UEP displays multidecadal variability that is consistent with the 20th century variability of the PDO and IPO. The UEP is then used to describe changes in ENSO variability which have occurred since 1650 focusing on changes in ENSOs variance, multiyear ENSO events, PDO-like multi-decadal variability and the effects of volcanic and solar forcing on ENSO. We find that multi-year El Niño events similar to the 1990-1995 event have occurred several times over the last 3 1/2 centuries. Consistent with earlier studies we find that volcanic forcing can induce a statistically significant change in the mean state of ENSO in the year of the eruption and a doubling of the probability of an El Niño (La Niña) event occurring in the year of (three years after) the eruption.

Assessing the impact of large volcanic eruptions of the last millennium (850–1850 CE) on Australian rainfall regimes

“…The NINO3.4 response found in this research supports previous studies by Adams et al (2003), Mann et al (2005), Emile-Geay et al (2008), McGregor et al (2010 and Maher et al (2015), despite GISS modelling weaker SST anomalies than observations (Fig. 1a, b).…”

“…In addition, a statistical relationship has been demonstrated between explosive tropical volcanism and ENSO where large tropical eruptions can increase the likelihood and amplitude of an El Niño event in following years, followed by a weaker La Niña state (Adams et al, 2003). Further work by Mann et al (2005), Emile-Geay et al (2008), McGregor et al (2010),812 S. A. P. Blake et al: Large volcanic eruptions of the last millennium (850-1850 CE) on Australian rainfall regimes result. Pausata et al (2015) and Stevenson et al (2016) identified that a radiative forcing threshold value of more than 15 W m −2 is required to affect the ENSO, and that high latitude Northern Hemisphere eruptions, in addition to tropical eruptions, are capable of doing so, as long as the forcing is asymmetric with regards to the equator.…”

A probabilistic model of chronological errors in layer-counted climate proxies: applications to annually banded coral archives

“…2 demonstrates how miscounting errors may produce an apparent amplitude modulation of otherwise stationary signals, producing spurious trends in the average derived from them. Because climate reconstruction methods rely in some fashion on a weighted average of observations assumed to be contemporaneous, this may partially explain why many ENSO reconstructions (e.g., Mann et al, 2000;Wilson et al, 2010;McGregor et al, 2010;Li et al, 2011; display increasing trends in ENSO variance over time (McGregor et al, 2013). As pointed out in the latter study, computing ENSO variance on individual records prior to averaging them together is more robust to chronological errors.…”

Multi-proxy reconstructions of May–September precipitation field in China over the past 500 years

“…Multiple ENSO and PDO reconstructions focused on the past millennium have been assembled in our previous work (Shi et al, 2017). Without loss of generality, we selected three reconstructed ENSO indices (Cook et al, 2008;McGregor et al, 2010;Li et al, 2013a) …”