20150728 - ozone layer

What if? Success in Protecting the Ozone Layer

May 26, 2015

by Molly Michelson

Located 20-30 kilometers (or 12-19 miles) above Earth in the stratosphere, the ozone layer works to protect life on Earth by absorbing most of the harmful ultraviolet (UV) radiation coming from the Sun. In the late 1970s and early 1980s, scientists discovered zones of ozone depletion over the Antarctic and Arctic (dubbed “holes”), due to hardy chlorine- and bromine-containing chemicals. Remarkably, an international treaty, the Montreal Protocol, was put into place quickly in 1987 to ban these substances. Amendments and adjustments have only made the treaty stronger, and now, all 197 countries are part of the ban.
In fact, atmospheric concentrations of these harmful substances peaked in 1993 and have subsequently declined. But what if the treaty weren’t in place? What if we had continued to produce and emit these chemicals? Several studies have looked into this, including one published today in Nature Communications.


 http://www.calacademy.org/explore-science/what-if-success-in-protecting-the-ozone-layer