Iceland is shrouded in a permanent low-pressure system. Far to the south, the Azores are shrouded in permanent highs. Both pressure systems rock, from east to west and with ever-changing intensity, in the process controlling the North Atlantic's westerly winds. When the westerlies are strong, Europe's summers are cool, its winters are mild and rain is frequent. When westerlies are weak, rainfall decreases and temperatures become extreme, leading to summer heat waves and winter deep freezes.
These year-to-year variations in the North Atlantic are known as the North Atlantic Oscillation. Though in many ways mysterious, their effects are quite predictable and long established. A missionary in Greenland in the 18th century wrote of one such effect: "In Greenland, all winters are severe, yet they are not alike. The Danes have noticed that when the winter in Denmark was severe, as we perceive it, the winter in Greenland in its manner was mild, and conversely."
The North Atlantic Oscillation is but one of many on the planet. Others include the Pacific Decadal Oscillation, the El Nino/Southern Oscillation and the North Pacific Oscillation, all with their own chaotic characteristics, all having profound and well-known effects on the climate of their regions.
Thanks to the work of Anastasios Tsonis and his colleagues, we now know that these four separate and major oscillations can and do act in unison. And when they do, the world climate turns.
Prof. Tsonis applied mathematical procedures from chaos and network theory to the oscillations that occurred over the 20th century, for each of the four major oscillations. Out of the chaos, he found coherence. All four oscillations demonstrated independent characteristics most of the time, operating at different intensities and wave patterns in their own complex dynamics.
But several times they synchronized. And within those synchronized periods, they sometimes coupled to act in phase and in increasing strength. This increasing coupling strength culminated in dramatic climate shifts.
"The first synchronization of the 20th century occurred around 1910," Prof. Tsonis explains. "For almost three years, the coupling strength increased and then in late 1912 or early 1913, the synchronous state among the oscillations vanished. That coincided with a sharp increase in global temperatures."
Other synchronizations occurred in the 1920s and 1930s, but these were marked by an absence of increasing coupling strength, and the global temperature didn't shift. "In the 1940s, we again saw synchronization accompanied by increasing coupling strength, and we again saw a dramatic change in global temperatures -- this was the period of global cooling that is so often remarked upon, and which led some scientists to predict that we were entering a new Ice Age," Prof. Tsonis continues. For several decades, more synchronizations occurred, but without increasing coupling strength. The temperature continued to cool. "Then, in the late 1970s, we once more saw the phenomenon of synchronization among the oscillations, plus increasing coupling strength. When the synchronization ended, the climate turned again, and the current period of global warming began."
Climate change over the entire 20th century, Prof. Tsonis has convincingly demonstrated, see-sawed between cooling and warming periods, in sync with the regional oscillations. He did more, too. He applied the same mathematical mechanism to a state-of-the-art model that reliably simulates the activities of the same oscillations. The model -- the same one used by the United Nations' Intergovernmental Panel on Climate Change -- produced results consistent with his chaos-theory mechanism.
"In the simulation over the next century, the climate shifts twice: first a cooling period beginning in 2027, and then a warming period beginning in 2065," he states. Moreover, the shifts in global temperature are independent of human activities.
"The model shows that the climate changes are intrinsic to the natural climate system," he elaborates. "Man-made activities doubtless also influence the climate, but not through the profound synchronizations that have foretold the climate in the past and will foretell it in the future."
--- - Lawrence Solomon is executive director of Urban Renaissance Institute and Consumer Policy Institute, divisions of Energy Probe Research Foundation.
CV OF A DENIER:
Anastasios Tsonis, a mathematician at the University of Wisconsin-Madison's Department of Mathematical Sciences, was among the first scientists to promote the application of chaos theory and nonlinear data analysis to atmospheric sciences and the first scientist to apply the concepts of "small-world" networks to atmospheric sciences. He originated or co-originated the Tsonis criterion, the Tsonis-Elsner method and the Elsner-Tsonis test. Early in his career, he developed a method of estimating rainfall from satellite images that is still being used today. Prof. Tsonis, the author or co-author of some 160 publications, received his Ph.D. in meteorology from McGill University.