LV Sketchbook Page 018 (Ozone)

In the midst of distressing environmental reports, NASA revealed some positive news this month: The ozone hole over Antarctica shrank to its smallest size since 1988. 

Paul Newman, chief Earth scientist at NASA's Goddard Space Flight Center, said in a statement that stormy conditions in the upper atmosphere warmed the air and kept chemicals like chlorine and bromine from depleting much ozone. Although this year's drop is mostly natural, it is also consistent with a trend of small steady improvements likely resulting from a 1987 international treaty banning ozone-eating chemicals used in refrigerants and aerosol cans. The ozone hole hit its highest point in 2000 at 29.86 million square kilometers (11.5 million square miles).

Ozone is generated in the stratosphere by the interaction of the sun's ultraviolet (UV) radiation with molecular oxygen. Most ozone lies in the lower stratosphere between 15 and 30 km in altitude where it absorbs the harmful radiation that causes skin cancer, crop damage, and other problems. United Nations scientists determined that without the 1987 treaty, ozone depletion would have contributed an extra 2 million skin cancer cases by 2030.