Life under threat as more ultraviolet radiation to hit earth

Concentrated in the stratosphere from 10 km to 50 km above the earth, the ozone layer protects life on the planet by absorbing more than 90 percent of deadly ultraviolet rays coming from the sun. Ultraviolet rays cause genetic changes and trigger various cancers.

Writing in Nature Geoscience on Sunday, University of Toronto researchers Theodore Shepherd and Michaela Hegglin warned that rising temperatures will change the circulation of the earth's upper atmosphere.

In their computer-generated model to highlight the impact of climate change in the next 100 years, the researchers said rising temperatures will cause a marked increase in the movement of ozone from the earth's upper to lower atmosphere.

As a result of ozone's climbing down, there would be less ozone in stratosphere (higher sphere) to protect humans from ultraviolet rays. They estimated as much as 20 percent increase in ultraviolet radiation hitting high altitudes in the Southern Hemisphere in the spring and summer.

More ultraviolet rays hitting the Southern Hemisphere will also cause an upsurge in biological changes and cancers, the researchers said. They warned that more ultraviolet radiation will also deeply impact air quality, and human and ecosystem health on earth.
However, the distribution of the ozone layer will help the Northern Hemisphere of the earth.

The model showed a nine percent decrease in ultraviolet radiation hitting Northern Hemisphere's high latitudes. Reported increase in the ground-level ozone on Europe's mountains and the west coasts of North America and Europe indicates that the deadly changes predicted by the two researchers may have already begun.

Interestingly, ozone is created in the earth's outer atmosphere by ultraviolet rays themselves. On entering the stratosphere, these ultraviolet rays hit oxygen molecules, breaking them into two atoms. But being unstable, each of these two atoms clings back to the oxygen molecule, thus creating ozone molecules.

Greenhouse gases (nitrous oxide and hydroxyl) and chlorofluorocarbons (generated by air-conditioners and refrigerators), which are capable of rising into the stratosphere, have been blamed for the depletion of the ozone layer.