ozone depleting substances ods methyl bromide the agriculture industry is still fighting for methyl bromide they argue they can't live without it in southern california we used to have still have the remains of a strawberry industry i can remember when if you drove eastwoodsong catella spring into orange county you went through strawberry fields now it's big industrial buildings but anyway the strawberries are grown under black plastic the black plastic helps keep moisture from evaporating away it helps keep the soil warm so the plants grow faster and it means that the strawberries aren't getting muddy in the dirt they're clean when you come to pick them trouble is underneath that black plastic bugs that chew on roots and kill the plants can flourish so what the industry likes to do is to plow up the field prepare it then come along with a jig with nozzles that they go into the ground squirt methyl bromide into the ground let that kill all the bugs and a day or two later roll out the black plastic and plant strawberry plants all the methyl bromide of course diffuses out of the soil and into the air i'm not quite sure where that is at the moment they're going to have to give it up it is going to be banned whether at this point it has been or is still going to be in the future i'm not certain but that's another thing that we're taking care of so yeah today we're mopping up um dealing with the last substances that contribute to the ozone depletion problem so what result has all this action had the level of freon measured in the air around us continued to rise for a while after 1995. naturally appliances were still leaking freon into the into the air but the rise slowed down somewhere in the early 2000s it topped out and today it's going down meanwhile up until two years ago anyway the antarctic ozone hole still getting bigger and more serious every year huh so we've solved the problem and we're seeing improvement but the antarctic goes on hold is getting worse how does that make sense but it does make sense because of the size and structure of the atmosphere okay here's the earth surface here we are the first 10 miles of the atmosphere called the troposphere weather climate airplanes all of the troops above that is the stratosphere which is where the ozone layer is located there's a region within the stratosphere called the ozone layer if you remember the amount of ozone there is absolutely tiny but it's more than there is anywhere else so why do we have these zones of the atmosphere because they already are separate it's not just scientists desire to name things the air in the troposphere basically stays in the troposphere it doesn't mix to any great extent with the stratosphere when we leak freon or any other substance we leak it from the surface into the troposphere how long before it reaches the stratosphere because of this lack of mixing on average about 20 years 20 years before it begins to cause a problem which is why we were able to start using freon in 1930 ramp up the usage through the 40s 50s and 60s it wasn't until 1970 that we even got an inkling we could have a problem and we didn't really see the problem until 1980. big delay built in but now here comes the key problem from the last of freon's wonderful features remember i said freon was colorless odorless non-toxic non-flammable and very stable wonderful for the shelf life of your products but freon has a lifetime in the atmosphere of about 100 years so after spending 20 years getting to the stratosphere the that freon still has maybe 80 years to go on destroying ozone and the chlorine atoms that are part of that freon think of them like little pac-man chewing up ozone molecules one after another for 80 more years okay so in the stratosphere here the amount of freon is now decreasing but think about it if it's so hard to get it from the troposphere into the stratosphere the amount of freon in the troposphere is much greater then the amount in the stratosphere so even though here it's topped out and starting to go down at this boundary there is still more freon on this side and less on that side so at this boundary freon is still moving into the stratosphere so the amount of rheon in the stratosphere where it does the damage is still going up as the amount in the troposphere comes down eventually it will reach the same as the amount in the stratosphere after that they'll come down together and actually the last two seasons the ozone hole in the antarctic has not got any worse after one season could be a coincidence i wasn't prepared to say anything after two seasons i begin to saying maybe we've reached that point where levels in both the troposphere and the stratosphere can start coming down together how long before the freon is gone most artists are estimating another 50 to 70 years the bottom line therefore is ozone depletion is solved it's the only big environmental issue that humanity has come together and solved and basically we're waiting for the solution to take effect the atmosphere is big and complex it's going to take a long time but the fix is in unfortunately you are going to have to use extra sunscreen take precautions basically for the rest of your lives but your children grandchildren ought to inherit a world where ozone depletion is no longer an issue for the time being it is very serious in australia which is relatively close to the antarctic they have experienced an increase of 400 percent in skin cancers 400 in several australian states they have draconian regulations in place for children school children at recess lunch are not allowed outdoors unless they are wearing long sleeves and hats and sunscreen all three or they stay indoors australia's taking it seriously