In the mid-1970s, a climate shift cooled sea surface temperatures in the central Pacific Ocean and warmed the coast of western North America, bringing long-range changes to the northern hemisphere.
After this climate shift waned, an era of frequent El Ninos and rising global temperatures began.
Understanding the mechanisms driving such climate variability is difficult because unraveling causal connections that lead to chaotic climate behavior is complicated.
To simplify this, Tsonis et al. investigate the collective behavior of known climate cycles such as the Pacific Decadal Oscillation, the North Atlantic Oscillation, the El Nino/Southern Oscillation, and the North Pacific Oscillation.
By studying the last 100 years of these cycles' patterns, they find that the systems synchronized several times.
Further, in cases where the synchronous state was followed by an increase in the coupling strength among the cycles, the synchronous state was destroyed. Then. a new climate state emerged, associated with global temperature changes and El Nino/Southern Oscillation variability.
The authors show that this mechanism explains all global temperature tendency changes and El Nino variability in the 20th century.
Title: A new dynamical mechanism for major climate shifts
Authors: Anastasios A. Tsonis, Kyle Swanson, and Sergey Kravtsov: Atmospheric Sciences Group, Department of Mathematical Sciences, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, U.S.A.
Source: Geophysical Research Letters (GRL) paper 10.1029/2007GL030288, 2007
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