Global climate change during the 13,500-b.p. Gothenburg geomagnetic excursion

ROBERTS and Olsen 1 suggested that high latitude atmospheric ionisation has an important role in nucleating cirrus clouds. And Harrison and Prospero 2 deduce that, if this is correct, severe drops of the Earth's magnetic field strength, such as are believed to accompany reversals, would lead to increased upper atmospheric cloudiness at all latitudes and correspondingly to major climatic events. There is likely to be warming at high latitudes but considerable cooling in the middle latitudes, in a way analogous to the aerosols 3 .