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[music fades out] >>Paul: I'm going to tell
a real scientific and I think public policy success story,
and it's about the ozone layer. You can see the globe
here. We divide the atmosphere into a variety of layers.
The troposphere is the lowest layer, it's where all of our weather occurs.
The stratosphere is the next layer up, and that's what I'm going to really focus on, because that's
where most of our atmospheric ozone is located.
Now ozone is critical in our atmosphere because it screens ultraviolet radiation.
Ultraviolet radiation, these are energetic solar
photons, there are, they are strong enough
to break the bonds of biologically active molecules, like DNA
for example. So, if you decrease the amount of ozone,
which is screening this UV radiation,
you get more at the surface, and what that'll do is that you get,
you sunburn a little more quickly. For example a person like me,
I'm out for about 15 minutes and I'll get a sunburn. But it does a lot of other things.
It impacts crops, it can cause cataracts. There's a famous study
of water men out here on the Chesapeake Bay in which they found
that their amount of time on the bay was proportional
to the cataracts that they got. The longer you were out there, the more cataracts you got.
But that's extended exposure over the years. So ozone is really
a critical gas in our atmosphere.
In 1974, these two gentleman on the right, this is
Sherry Rowland, and this is Mario Molina. They proposed that there were
a class of gases being emitted into our atmosphere that
could destroy the ozone layer. These are chlorofluorocarbons, or CFCs.
So, they proposed this, and it was
quite controversial at the time. They took a lot of heat
because this chlorofluorocarbon industry, chemical industry,
was used in a variety of different kinds of products.
You can see some of these, many of us remember, it used to be used as a propellant
for hairspray, and deodorants. It was
used to make foam products, like these cups you would get
from McDonalds or other companies. It was used,
CFCs were used in air conditioning and in car air conditioners.
It was also, there's another kind of gas called a halon.
Halons are used in fire extinguishers, they contain bromine. They can also
destroy ozone. So this is proposed in 1974,
and there was a huge amount of energy and effort that was going in
the late 70s and early 80s to see what the impact
is on ozone, to measure ozone and these gases in particular.
Now, in 1985, there was a publication
of a paper on ozone down over Antarctica.
And these three gentleman here, this is Joe Farman,
Brian Gardiner, and John Shanklin. They're standing in
front of an instrument that measures the total amount of ozone between the surface and space.
And they published their data. And you can see it here,
this is a measurement, this is the total amount of ozone between
the surface and space over the station. It's Halley Station down in Antarctica.
And what that shows is that the level of ozone
was dropping and it was dropping really fast. Okay.
It was an amazing study that they published, and the quality of these
data are such that there was no dispute to this. Ozone
was going down, and it was going down fast. This was a real shock
to the atmospheric community, when this paper was published.
Shortly thereafter, and this was in the,
in 1985 also, a scientist at the NASA Goddard
Space Flight Center P.K. Bhartia made an image
of what this ozone looked like over Antarctica.
And so you can see Antarctica here in the center, South America, Africa,
Australia, and here in the middle is this very low ozone area,
these red colors and yellows that you see here indicate very low ozone.
And it was dubbed "the Antarctic ozone hole".
So ozone was going down fast, and it was a huge region.
This is a very large region, comparable to, this continent of
Antarctica is a large area, so there's a large depletion over
a large area. And we didn't actually understand what was going on at the time.
But within a couple of years, we figured out it was actually due to these
chlorofluorocarbons and halons.
So there was a lot of consternation about this. What are we going to do? How can we
stop it? What are other measurements can we make? So the rising
concern about the problem amongst the nations of the world,
there was already discussion about, should we get together and create an agreement?
And in fact after a couple years, they did create an agreement.
This is an agreement called
the Montreal Protocol.
These are, this is a, this shows a meeting of the parties to the Montreal Protocol.
took place in Doha, in the Saudi Arabia peninsula
And here you can see the Montreal Protocol had a series of
agreements the initial one, and they were added on to, further
strengthening regulations of these chlorofluorocarbons. So eventually,
the production of chlorofluorocarbons and halons
was fully agreed to. Now, you can see the nations of the world,
there are little signs here. Here you can see, this is me sitting
way in the back of this meeting. Even though
the scientists, we bring them all the information, we're always put at the back of
the meeting. When they need us, they'll call on us, but we sit in the back and listen
to all the discussions. And mostly these discussions are about countries'
ability to maybe use a CFC for a short time. There are a lot of different
things going on in these meetings.
Okay. So now what's happened with ozone. Well first of all
let me talk about chlorine. So chlorine,
it was going up and up and up through the 1960s, 1970s, 1980s.
These are a combination of all the CFCs and halons. And then the
Montreal Protocol was signed here in 1987, and
slowly those regulations began to take hold, and in fact
the projection is that these
ozone-depleting substances are going to decline with time. Now this is going to take a long time,
because CFCs, these chlorofluorocarbons have long lifetimes.
For example, CFC 11 has a lifetime of about
52 years. CFC 12, which was used in
your car air conditioners, has a lifetime of over 100 years.
So it's going to take a long time, even though the production and emission
of these gases has been regulated, it's going to take a long time for them
to come out of our atmosphere.
So what's happening with ozone now? So this is showing
this is in percentage, the change of ozone over time in percentage.
You can see the observations as you go into the 80s. You can see
that ozone was going down, the CFCs were increasing,
the Montreal Protocol is signed here. Pretty soon the chlorine
has started to decrease, and you can almost,
there's a Mt. Pinatubo effect right here, but you can almost see that ozone isn't going
down anymore, and maybe there's a hint that things are starting to go
up. We can't say that, as scientists we can't that's true yet,
but I think we're getting to the point, within the next few years, I think we'll actually
be able to say statistically that ozone is increasing
in our atmosphere. Let's keep our fingers crossed.
Now, the other way of looking at this is we can use a model
to take a look at what would have happened to ozone if we'd done nothing.
So I'm going to show you a little model study here. And on the top left, I'm going to show you
the expected world. And this is with the Montreal Protocol,
CFCs are going to decline. Over here is what we call "the world avoided".
And this is chlorine going up. If you look on the picture,
you can see the amount of chlorine in the expected world and the amount of chlorine
in the world avoided. So you can see here it's 4.5, there it's
already a little bit higher because of the Montreal Protocol,
this is because of the Montreal Protocol, that's without one. And you can see this flying by
fairly quickly, as you can see the date on the right, you can see the ozone hole appearing
every year. Chlorine continues to go up in this
world avoided, and now you can actually see it peaked down at about 4
and it's in a slow decline as we're out to 2022, 24.
If you look here at this world avoided you can now start seeing a little ozone
hole deep low values appearing over the Arctic.
And you see the very very large ozone loss
in over the Antarctic region. If you look at the expected world,
you don't see any of those things. And in fact this chlorine continues to increase,
you can see ozone going down now in the tropics
and in the subtropics. So you can see that here you're dominated by reds and
oranges, the higher ozone levels. In the world avoided, you can see
that ozone is declining and declining and declining.
Now, this is about 40 to 50 times, by the time you get
out to 2065 here, this 40 to 50 times
the natural level of chlorine in our atmosphere. Chlorine and bromine
combined. And this has gone down, it about needs to go down to
about 1.2, this is about halfway there. But you can see
the difference in ozone. 65 per-, or excuse me, about two
thirds of the ozone layer is destroyed if there had been no
Montreal Protocol, if nothing had been done. Okay. Now what does that mean?
That means huge impacts on crops.
For somebody like me, I mentioned that if I go outside, 15 minutes I'll get a
perceptible burn. In that world it's 5 minutes. Okay.
So you go out and you walk for a quarter of a mile, you would get
a perceptible sunburn. So, this is an
incredibly bad world, we don't want to live in that world. This is the one that
we expect. Now, we can do,
as I've already shown, we can do these projections of where ozone is going.
Here we can see the observations, this shows a model projection,
and now I put two model projections on here. The lower one is
a world in which both ozone-depleting substances,
it has a Montreal Protocol in it, they've been regulated and so ozone is
going up. But in one, greenhouse gases are regulated.
In the other, greenhouses gases continue to go up.
And in fact, ozone continues to go up. So,
the net impact of increasing greenhouse gases is that the ozone layer begins to pile
up lots of ozone. So instead of a depleted ozone world, we're going
to go to an ozone world where there's probably too much ozone.
Now what does that mean for the environment? I actually don't know. I don't think we
know as scientists what's going to happen there.
So let me say another word about
what happened. This is, I love this picture,
I owned a 1967 Ford mustang fastback. It was
a hot car. I love this car. It has a CFC air conditioner in it.
So I was using CFC-12 in that
particular air conditioner. Here is a Tesla, a modern Tesla.
It uses a replacement compound called an HFC,
in fact HFC-134a. And in fact in all your cars right now,
you have that particular refrigerant in your
car air conditioner. So this is the compound that replaced the CFCs.
Now the beauty of this is this is a hydrogen, a fluorine, and a carbon.
It doesn't have chlorine, so it doesn't destroy the ozone layer.
The problem with HFCs though is they're greenhouse gases.
The particular HFC 134a is about,
pound for pound, it's about 14 hundred times more
efficient at warming than CO2.
So you could take one pound of this HFC-134a,
is equivalent to about 14 hundred pounds of CO2.
So the replacement compounds for the CFCs
are greenhouse gases. And the question is, what are we going
to actually do about these? Now this shows a particular HFC, this is HFC-23.
You can see these are observations they're increasing with time. Because we
replaced the CFCs. There are many other HFCs.
This is the one I talked about, it's in your car air conditioner, 134a.
This one 32 and 125, these are probably
in your home air conditioning units. So all these HFCs
are increasing with time, and these HFCs are all
powerful greenhouse gases. So, we solved the problem,
that is the problem of ozone depletion, but in fact, and in fact those
CFCs were also powerful greenhouse gases, but we replaced them with compounds
that are also powerful greenhouse gases.
So you could do a lot for climate if you figured out how
to take these compounds and replace them with compounds that are both
friendly to the ozone layer and friendly to climate. And in fact
there are technological solutions. So that goes back to the Montreal Protocol.
The Montreal Protocol could in fact take action on these
HFCs. We don't know that that's going to happen, but it might.
So let me kind of summarize
where we've been. So I told you a good story. We got rid of these
CFCs, they're now regulated, they still exist in various places around the atmosphere,
but they're slowly declining. That's a great story. In fact, the outcome
of that would have been an environmental disaster
if they had kept growing. We used a lot of satellite information
to take a look at the ozone problem. Most of the observations
you've seen on this presentation have come from NASA
satellites, including the Aura satellite that you can see here.
Now what does the future hold? Well, the future's in our own hands.
We have two things we can, you can regulate these compounds,
and that may happen. But the one thing that we really need to do
is we need to continue to look at the atmosphere continue to make measurements
of what's happening to our atmosphere. And that's where satellites like Aura
and its follow-ons are crucial to knowing where we're going to be in the future.
Thank you. [applause]
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