Time series of solar activity (bottom) and the North Atlantic Oscillation in two
model simulations, without (blue) and with (yellow) solar forcing. Graphics, GEOMAR.
Long-term climate variability in the Northern Hemisphere linked to solar variations
(September 15, 2015) The natural, 11-year cycle of solar activity is apparently influencing long-term climate fluctuations in the Northern Hemisphere. An international team of scientists led by GEOMAR Helmholtz Centre for Ocean Research Kiel showed that the so-called North Atlantic Oscillation, one of the dominant circulation patterns on the Northern Hemisphere, is phased-locked to the decadal solar activity with a delay of one or two years. The study appears today in the international journal Nature Communications.
Are climate predictions over periods of several years reliable if weather forecast are still only possible for short periods of several days? Nevertheless there are options to predict the development of key parameters on such long time scales. A new study led by scientists at GEOMAR Helmholtz Centre for Ocean Research Kiel shows how the well-known 11-year cycle of solar activity affects the long-time development of dominant large-scale pressure systems in the Northern Hemisphere.
For their investigations the scientists used a coupled ocean-atmosphere model. In addition, this model includes an interactive chemistry module which can for instance cope with the effect of ultraviolet radiation (UV) in the upper atmosphere. This additional component seemed to be key to transmit the variations in the solar radiation which might have only a small direct impact on the earth's surface, through a complex mechanism from the stratosphere (10-50 km altitude) to the lower atmosphere.