Big Air Circle Ballad

Georgy Falster

In western seas
at low degrees,
converging breeze
lifts air with ease.

The ocean’s warm,
so water’s drawn
to clouds that form
convective storms.

That air flows east,
aloft - at least 
until the 
temperature’s decreased.

Then, cool & dry
falls from the sky,
to make a zone
where pressure’s high.

And next: this air,
it doesn’t rest,
it turns around
and heads back west.

Closing a ring
of air that spins
around, and brings
some different things:

if it spins slow
that’s weaker flow
of air - and so
earth’s rain clouds go

to different spots:
so ‘wet’ or ‘hot’
depend a lot
on ‘slow’ or not.

Of course the
opposite is true;
a faster spin
moves rain clouds too.

And so you see
this air ring’s key
for knowing where 
Earth’s rain could be.

But this ring of air,
it doesn’t care; 
it makes me swear
and pull my hair.

Earth’s getting hot;
So many watts!
But will this thing
respond or not?

Will it get weak?
Or will speed grow?
We’ll only know
as more time goes.

There’s just no trend!
Well, it depends,
in fact, on where
you put your ends.

But stats say ‘no,
that’s just brought woe
so far’, and so
I’ve had a go;

looked back in time
800 years,
and it appears 
an answer nears.

There’s been no change
in trend or range;
the mean’s maintained,
so that explains

conflicting signs
from shorter times
where lines showed
increase & declines.

But a curiosity’s
that recently,
the frequency
of ring speed change

has changed—
it’s rearranged
itself, and that
we can’t explain. 

Ah—but there’s more
here that we saw,
that helps us guess
at what’s in store.

Here’s three main things
that drive this ring,
so we begin
to see within

our air ring’s heart— 
and hence we start
to tease the
forcings apart.

Volcanos flash,
releasing ash
that spreads and
makes a climate splash.

Earth shifts a gear
(just for a year
or two,
until the skies are clear).

And with that shift,
a sudden drift
in places where 
air’s sunk or lift.

The ring first slows,
and then speed grows,
and then returns
to normal flow.

And so this quick
volcanic ‘shift’?
It’s more a blip
than actual drift.

But it might be
that sky debris
in certain spots
gives our ring speed.

Clear out that dust, high
In the sky?
Then global heat
won’t have to vie

with forces driving
faster spin,
such that its
influence will win.

Then global heat
might have us beat,
cos it could make
the air ring weak.

And there’s no doubt
(I’ve shown throughout)
this ring’s got clout
moving clouds about.

Which means the places
where it rains
are going to change,
and cause some pain.

The Science

The Walker Circulation is a big atmospheric circulation system over the tropical Pacific Ocean, and it affects weather and climate worldwide. In fact, the Walker Circulation is one of Earth's most important climate features, but it is often overshadowed by its flashier, more famous sibling, the El Niño-Southern Oscillation. This poem summarises recent research, where we reconstructed how the Walker Circulation behaved in prehistoric time (since the year 1200). This gives us information about how the Walker Circulation behaved before humans started mucking around with the climate system.

We found that there has been no change in the overall strength of the Walker Circulation because of climate change (yet!), but this might be because of the competing influence of aerosol emissions. In the industrial era, there has been a subtle increase in the amount of time taken for the Walker Circulation to switch between when it spins slower (which causes El Nino-like conditions) and when it spins faster (which causes La Nina-like conditions). Also, we found that large volcanic eruptions cause the Walker Circulation to slow for a couple of years.  All of this helps us understand how the Walker Circulation might change with future climate change.

The Poet

Georgy Falster (she/her) is a climate scientist, currently living in Canberra, Australia. Outside science, Georgy's interests are many and varied: she enjoys reading, skiing, swimming, archery, running, camping, playing violin and guitar, and, occasionally, writing poems - mostly about her work.

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