Ozone layer breakdown of ozone in the stratosphere results in reduced absorption of ultraviolet radiation. Consequently, unabsorbed and dangerous ultraviolet radiation is able to reach the Earth’s surface at a higher intensity. Ozone levels have dropped by a worldwide average of about 4 percent since the late 1970s. For approximately 5 percent of the Earth's surface, around the north and south poles, much larger seasonal declines have been seen, and are described as "ozone holes". The discovery of the annual depletion of ozone above the Antarctic was first announced by Joe Farman, Brian Gardiner and Jonathan Shanklin, in a paper which appeared
Layer Jump Recording versa. Jumping layers is already necessary for reading multiple layer optical media (so far market released products are limited to two layers despite some research prototypes having up to eight layers), as well as for recording them with Sequential Recording. However the layer jump during the recording occurs only once, at the position called Middle Area, during a Sequential Recording, while it may occur multiple times with Layer Jump Recording. Two different Layer Jump methods are defined: Manual Layer Jump and Regular Layer Jump. The first require the software to specify to the hardware each jump point from layer zero