An increase of storminess seems to be the key to the whole situation.

With the change in storminess there naturally goes a change in rainfall.

The net result is that when sunspots are numerous the earth's storminess increases, and the atmosphere is thrown into commotion.

As a matter of fact the storminess is notably greatest when the edges of the solar disk are most disturbed.

The diminution of snowfall on the ice sheets when storminess diminished was probably highly important.

The amount of precipitation on the sheets was presumably lessened still further by changes in the storminess of middle latitudes.

Therefore a diminution of storminess would be particularly effective in causing the disappearance of ice sheets in these regions.

Suppose, however, that a diminution in storminess combined with other conditions should permit corals to grow in latitude 70°N.