<P> Ozone depletion describes two related events observed since the late 1970s : a steady lowering of about four percent in the total amount of ozone in Earth 's atmosphere ( the ozone layer ) , and a much larger springtime decrease in stratospheric ozone around Earth 's polar regions . The latter phenomenon is referred to as the ozone hole . There are also springtime polar tropospheric ozone depletion events in addition to these stratospheric events . </P>
<P> Ozone depletion describes two related events observed since the late 1970s : a steady lowering of about four percent in the total amount of ozone in Earth 's atmosphere ( the ozone layer ) , and a much larger springtime decrease in stratospheric ozone around Earth 's polar regions . The latter phenomenon is referred to as the ozone hole . There are also springtime polar tropospheric ozone depletion events in addition to these stratospheric events . </P>
where are the holes in the ozone layer located
where are the holes in the ozone layer located
around Earth 's polar regions
around Earth 's polar regions