Model of solar activity with non-stationary harmonics and long-term climate variability

It is very important to distinguish long-term solar and anthropogenic effects to provide reliable and accurate estimates of space radiation environment. A method of non-linear spectral analysis, named by the method of the global minimum (MGM) has been used to find periodicities in the annual Wolf sunspot numbers W from 1700 to 1993. Calculated model shows that solar activity exhibits complicated behaviour with different time scales and episodes of reduced activity in the past and in the future (similar to Maunders minimum), nonstationary behaviour of the defined harmonics. Most power spectral peak is non-stationary triplet with T about 250 yr. (which is twice as large as the second spectral peak at T similar to 11 yr.). Our study demonstrates that this peak consists of three unresolved (due to confluence of error bars) sinusoids. This triplet corresponds to the behaviour of the slowest processes occurring during the studied period. Well-known data about global climate are used for comparison with solar activity. The long-term curve of the solar activity explains global climate changes in the past: (the epoch of the Little Ice Ages, global climate warming from the beginning of this century). Other data about average temperatures of air and ocean confirm this model. It is shown that global increasing of solar activity (which began at the beginning of the present century) is finished. The evolution of the 23(rd) cycle will occur after beginning of depression of average activity. Such behaviour suggests the approach to the Cold Epoch (in the 21(th) century the solar activity level will be less).