The smaller the angle, the less seasonal variation experienced on earth. The following figures gives a graphic illustration of these cyclical effects known collectively as the Milankovitch theory. The Eccentricity Effect and the Precession and Obliquity Effects Together these Milankovitch cycles were thought to be the driving force behind long term ice ages and global warming patterns. Today, with improved mathematical modeling of global climates, it appears that these changes are not enough to trigger a major glaciation or ice cap melt. However, these cycles combined with differences in albedo, sea surface temperature, and other secondary factors could lead to significant changes in global climate.
Climatic changes can also arise due to volcanic eruptions.
While this may not sound like much, on a global scale this can have strong effects. The reason for this cooling lies in the fine particles of ash and dust that are released into the air. These particles tend to reflect more solar radiation away from the earth, much the same way clouds keep you cooler in the summer. These particles also combine with water vapor to produce a haze of sulfuric acid particles that can have climatic influences for several years before dissipating. A third cause of climatic variation results from changes in solar output.