Natural processes can cause huge changes in carbon dioxide

Natural processes, such as volcanism,chemical weathering of rocks,and the burial of organic matter,can cause huge changes in carbon dioxide when they continue for millions of years.Over the past million years, carbon dioxide has been relatively low,and repeated glacial maxima have been caused by cycles in Earth movement around the sun.As Earth rotates,it wobbles on its axis and its tilt changes,altering the amount of sunlight that strikes different parts of its surface.