Dr. Henrik Svensmark found the following correlation between incoming cosmic rays (blue) and the average temperature of the sea (red):
Quite a correlation, isn’t it? The light blue bars indicate when the earth moved through one of the arms of the galaxy. These arms cause an increase of cosmic rays, and Dr. Svensmark proved that these rays – when they hit the water – are responsible for forming clouds, which in turn cool the earth. So because the earth moves through an arm of the galaxy, we get cold.