Abstract
Despite evidence from a number of Earth systems that abrupt temporal changes known as regime shifts are important, their nature, scale and mechanisms remain poorly documented and understood. Applying principal component analysis, change‐point analysis and a sequential t‐test analysis of regime shifts to 72 time series, we confirm that the 1980s regime shift represented a major change in the Earth's biophysical systems from the upper atmosphere to the depths of the ocean and from the Arctic to the Antarctic, and occurred at slightly different times around the world. Using historical climate model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) and statistical modelling of historical temperatures, we then demonstrate that this event was triggered by rapid global warming from anthropogenic plus natural forcing, the latter associated with the recovery from the El Chichón volcanic eruption. The shift in temperature that occurred at this time is hypothesized as the main forcing for a cascade of abrupt environmental changes. Within the context of the last century or more, the 1980s event was unique in terms of its global scope and scale; our observed consequences imply that if unavoidable natural events such as major volcanic eruptions interact with anthropogenic warming unforeseen multiplier effects may occur.
Highlights
IntroductionSubstantial and persistent changes in the state of natural systems
Regime shifts are abrupt, substantial and persistent changes in the state of natural systems
Using historical climate model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) and statistical modelling of historical temperatures, we demonstrate that this event was triggered by rapid global warming from anthropogenic plus natural forcing, the latter associated with the recovery from the El Chichon
Summary
Substantial and persistent changes in the state of natural systems. There is a considerable research gap with many disparate observations by different scientific disciplines, but no comprehensive overall assessment We address this gap by focusing on the 1980s regime shift and show, using three independent statistical methods that this shift took place on a planetary scale and involved the carbon cycle (Beaulieu et al, 2012b); disease (Vezzulli et al, 2012); and biotic, physical and chemical components of land (Myneni et al, 1997; Brandt et al, 2013), freshwater (Hari et al, 2006), precipitation (Tao et al, 2015), marine (Mo€llmann & Diekmann, 2012; Beaugrand et al, 2015) as well as cryospheric (Brown & Robinson, 2011) and atmospheric (Lo & Hsu, 2010; Xiao et al, 2012) Earth systems. A total of 72 time series was processed and analysed statistically to represent as many natural systems as possible, and to illustrate shiftlike abrupt changes in a ‘1980s period of interest’ (1983 to 1990) between the volcanic eruptions of El Chichon and Pinatubo (see Materials and methods)
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