How is the sunspot cycle directly relevant to us here on earth? the sunspot cycle is the cause of global warming. coronal mass ejections and other activity associated with the sunspot cycle can disrupt radio communications and knock out sensitive electronic equipment. the brightening and darkening of the sun that occurs during the sunspot cycle affects plant photosynthesis here on earth. the sun's magnetic field, which plays a major role in the sunspot cycle, affects compass needles that we use on earth.