The gravitational forces from changes in the positions of other planets change the tilt of the Earth s orbit. Jupiter and Venus affect on Earth s orbit the most. Jupiter because of its large mass and Venus because its relative proximity to Earth. The researchers found that the Earth experiences ice ages when its orbit is less tilted and warm periods when it is more tilted. The first guess is dust.
Dust hitting the Earth has the same cycles as the ice ages.
Remarkably, cloud formation is not well understood. Muller does not discount manmade global warming, however. The bleaching of coral reefs has been touted as one of the consequences of global warming. In a previous issue we highlighted a study that showed that coral bleaching may be part of a natural cycle. That finding now seems to be confirmed with the recovery of coral reefs throughout the world.