Depleting Ozone May Lead to Increased Ultraviolet Radiation on Earth

A team of US and German researchers has measured the highest level of ultraviolet radiation ever recorded on Earth's surface - in the Bolivian Andes - and their study indicates that depleting ozone may be what caused such harmful radiation levels.

Only 1,500 miles from the equator, the Bolivian Andes boasted levels far above those normally considered to be harmful to both terrestrial and aquatic life. Using the European Light Dosimeter Network (Eldonet), researchers came to the surprising realization that South America, of all places, demonstrated record ultraviolet (UV) fluxes in the summer of 2003 and 2004.

"These record-setting levels were not measured in Antarctica, where ozone holes have been a recurring problem for decades," lead author Nathalie A. Cabrol of the SETI Institute and NASA Ames Research Center said in a statement. "This is in the tropics, in an area where there are small towns and villages."

The measurements were taken as Cabrol's team was investigating high altitude Andean lakes as part of an astrobiology study of Mars-like environments. The combination of midday sun and high elevation of these Bolivian mountains - some 20,000 feet above sea level - produced higher irradiance levels because of naturally low ozone in such locations.

"A UV index of 11 is considered extreme, and has reached up to 26 in nearby locations in recent years," Cabrol noted. "But on December 29, 2003, we measured an index of 43. You simply do not want to be outside when the index reaches 30 or 40."

For comparison, if you are on a US beach in the summer, you may experience an index of 8 or 9.

Researchers speculate that this increased UV flux may have been caused by ozone depletion - a result of increased aerosols from both seasonal storms and fires in the area. Also, a large solar flare occurred just two weeks before the highest UV fluxes were registered. While the evidence linking the solar event to the record-breaking radiation is only circumstantial, particles from such flares are known to affect atmospheric chemistry and may have increased ozone depletion.

"While these events are not directly tied to climate change, they are sentinels of what could occur if ozone thins globally," Cabrol explained. "The thinner and more unstable the ozone, the more prone we will be to this kind of event."

Cabrol and his colleagues, who published their study in the journal Frontiers in Environmental Science, believe that ozone levels should be more closely monitored, as this sort of event could happen again, "because the factors that caused it are not rare," he said.