Analysis of solar forcing of climate on long time scales has shown that it is necessary to take into consideration the influence of long-term solar cyclicity, such as 200 and 2300-2400-year cycles, on climate. Even in the relatively warm climate of the last 10,000 years, a tendency to climate cooling at deep minima of long-term solar cyclicity is observed. Along with this, a long-term solar forcing of climate manifests itself not only as an external factor due the influence of solar irradiance variations on the atmosphere-ocean system, but also as a stimulator of internal processes in the climatic system, which, in turn, can lead to abrupt climate change. Large-scale abrupt climate oscillations - warmings and subsequent coolings Dansgaard-Oeschger cycles - have been revealed in cores of Greenland ice for the interval 60,000-10,000 years BP. They are attributed to the ice-rafting events in the North Atlantic. A comparative analysis of the development of Dansgaard-Oeschger events and solar activity variations variations in the 10Be concentration in Greenland ice has shown that these climatic and solar processes developed simultaneously. It is evident that ice-rafting events were stimulated by an increasing ambient temperature and, hence, they are associated with a high solar activity level. A similar effect of solar activity has been revealed for the time interval of the Holocene. Thus, not only a low, but also a high level of solar activity was in the past a stimulator of abrupt climate changes.