The chlorine-based chemicals being produced and emitted into the atmosphere are sticking around much longer than expected and potentially affecting the ozone layer.

Atmospheric researchers had speculated that the level of chlorine in the stratosphere was decreasing, but a new study out of the University of Saskatchewan has finally determined by just how much.

Dr. Susann Tegtmeier explains that scientists have thus far been using ground-based measurements to forecast how fast ozone-depleting substances like chlorine are dissipating. Now, using an instrument on board the Canadian SCISAT satellite, Tegtmeier says her team has found that chlorine in the stratosphere is decreasing 25-30 per cent slower than originally expected.

She says the discrepancy occurs because the ground measurements that have been used only look at ‘long-lived’ chemicals. These substances are banned under the Montreal Protocol, so they are decreasing in the stratosphere. However, the presence of ‘short-lived’ substances, such as dimethyl chloride, which are not banned, is on the rise, but not included in the ground-based recordings.

“We’re really the first ones who were able to put some numbers on this. It’s not just two per cent or three per cent, it’s about one quarter of the decrease in stratosphere chloride that we don’t see, because we actually omit all the short-lived substances.”

Tegtmeier hopes her data contributes to the start of a discussion regarding the use of short-lived substances, however she admits that it’s hard to say if the discovery will spark policy change.

“It’s very important to have these numbers, because they will be important when the Montreal Protocol parties discuss what should happen with these short-lived substances in the long term.”

Next steps for her research will be determining how significantly these substances contribute to the depletion of the ozone layer in the stratosphere with the help of an international team.