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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 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.
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, it's a 1967 Ford mustang. 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.
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