Every few months, a team from the Australian Government
science agency, CSIRO, and the Australian Bureau
of Meteorology will bottle up air from here,
at the northern tip of Tasmania, and send it off to be archived. A few days ago, back on the
Australian mainland, in a suburb of Melbourne, I interviewed one of the team
at the Air Archive to explain how and why. - The first tank was taken on
the 26th of April, 1978. All up, we have close to 200 tanks
spanning almost 50 years. The pressure they get to is
around-about 900 PSI. They're 34 liter tanks,
which means they hold around 2,000 liters of air
once they're completely full. - This place, Kennaook / Cape Grim,
has the cleanest air in the world... when the wind's blowing
from the south-west, when that air has traveled
thousands of kilometers across the Southern Ocean
without touching land. So that is a monitoring station, testing the levels of dozens of gases
and chemicals in the atmosphere. - When we say clean air
or baseline air, we mean that it has not had recent contact
with land or pollution sources. We know that it's very representative
of the mid-latitudes of the Southern Hemisphere
background air. Most of the sources of the
major greenhouse gases are in the northern hemisphere because that's where the
major population centers are. It takes about a year to do
the inter-hemispheric transport, going across the equator
is much, much slower than the mixing within a
hemisphere itself. We wait until the wind is coming
from the southwest direction, and normally we wait several hours. - Today, the wind is not blowing
in the right direction! It's blowing in from the cities in
Tasmania and the Australian mainland, but the team here are going
to do a "practice fill" of an archive cylinder, so they
can show you what would happen. And it's a really technical operation
that has to avoid contamination. - These cylinders are filled
cryogenically, under vacuum. When they're put into
the liquid nitrogen, the air naturally will be
sucked into the tanks over a two- to three-hour period. - As any gas cools down,
it compresses. So initially the air rushes in
to fill the vacuum, but then it hits
liquid nitrogen-chilled stainless steel, so it cools and compresses
and more air rushes in, which cool and compresses,
and so on, and so on and so on. It's a really clever way to fill
a pressurized canister without pumps. - We then let it
heat up or warm up, and then we blast whatever
water is in there out. There is water in the tanks because
there's water in the atmosphere, and we don't do any drying. We don't want to use pumps or any
particular drying agent or method, as this can potentially
contaminate the tanks. - So I had an obvious question:
how do they know that the air in the archive tanks
doesn't change over time, through some chemical reaction,
or osmosis through a faulty valve, or microbe contamination? - We take measurements
of the archive regularly, maybe once a year we'll
"take a sniff" out of each of the cylinders,
so to speak, to ensure trace gases are not
drifting or changing. There is a little bit of
moisture and water in there and there have been concerns
where the microbes might be changing the composition
for some trace gases. But from what we've
discovered so far, that's not really the case. - So they've got an archive.
What do they do with it? Well, let's say someone
discovers that actually, there's a greenhouse gas or
some other contaminant that we should have
been testing for, for the last 50 years or so. The researchers can
go to the archive, pull samples from the tanks, and use modern equipment
to test old air. Remember CFCs? They've been testing
for those on site here for years, but it turns out the replacements
also cause problems. - After the CFCs were the
interim replacements, HCFCs, and then the replacements
for those, HFCs. It's only recently
we've had the technology to be able to measure those, to build up a history
back in time to 1978. That would not be possible
without the archive. Some of the measurements we do take
just 20-30ml of air. We can actually take measurements
down to parts per trillion. - There was one more thing that
Paul showed me back at Melbourne. The first tank taken here in 1978? It's not the oldest one
in the archive. - Several years ago,
we did a media story, and we started to get inquiries
from the public saying, "we've got older air than you". And it turns out there was
a lot of people out there with old scuba tanks
sitting in their garages. And most scuba divers kept
a diary of when they dived, when and where the tank was filled. So people started to donate
their scuba tanks. So we now have air back to 1956. For some trace gases
that we're interested in, are perfectly fine to
take the measurements. - All right, I am... I'm standing somewhere windswept
and talking about infrastructure. It's like the fifth time! I'm amazed the microphone held up.
Thank you so much. - No worries!
It’s great seeing a video on tasmania that doesn’t involve fish or a grave
I honestly didn't even know that this was happening until Tom posted that video.