The Best Australian Science Writing 2014 (13 page)

‘Climate change is driving changes in sea levels, ocean chemistry, marine, terrestrial and aquatic ecosystems, agricultural production, water security and the frequency and magnitude of severe weather events,' the bureau told the 2013 Senate Inquiry. ‘Further change is now locked in for centuries, whether or not emissions are reduced or even halted in the near term.'

Neil Plummer says future weather may look much like it does today, but the frequencies and intensity of some events will be different. ‘There will be a lot more warmer weather … fewer occurrences of cooler weather, and the chances of warm-event records being broken will increase as time goes on,' he says. ‘The
models also suggest we should get increased frequency of intense rainfall events in many areas.'

So the long-term projection for Australia is more and longer heatwaves and droughts alternating with periods of heavier rain. This is likely to mean more bushfire weather and more flooding. Overall, though, wet years will become fewer and dry years more frequent, particularly in southern Australia. As for individual weather phenomena, scientists say only that there may be fewer tropical cyclones, though they are likely to be more intense.

Recent weather events have convinced many Australians of the reality of global warming. One who has needed no convincing is Mike O'Neill. Like many in the storm-chasing fraternity, he's sure weather events will become more extreme, and with that will come more potent lightning. ‘I doubt I will see these events in my lifetime, but if I do I will certainly be ready for them with camera in hand!'

We're 70 kilometres south of Darwin and it's 2.15 p.m. The sky looks less blue now. Puffy cumulus clouds are everywhere, some boiling up promisingly into cumulonimbus storm clouds. There's a big one ahead.

Half an hour later, on a hill just outside the town of Adelaide River, we get a grandstand view of the storm. It's building up at astonishing speed, 10 kilometres to the east of us. The radar image shows it blotched with orange and yellow, indicating moderate to heavy rain. Mike O'Neill and photographer Dave Hancock, who has been following us in his LandCruiser, set up tripods and cameras fitted with lightning triggers – devices that set off the shutters when they detect flashes.

At one point a vivid bolt zigzags out of the side of the storm and hits the ground well clear of it. The cameras go ape. ‘Wow, that was huge!' exclaims O'Neill. ‘It would have travelled at least 10 kilometres outside the storm. So we're within range.' Having had several lightning encounters that were too close for comfort,
he has nothing but respect for thunderstorms. Because of the danger, the bureau in no way encourages chasing, but it welcomes information that chasers provide.

By 5 p.m. a curtain of rain has dropped beneath the storm. The downdraft of cool air that it brings is spreading out and spawning new storm cells. Sure enough, the radar image has several more big cells lining up to the south-east. We hit the road again.

Come 6.30 p.m. we're parked beside the highway, 30 kilometres to the south. There are storms all around us. Lightning is stabbing the ground at all compass points and the tripod-mounted cameras are clicking away. We're right in the middle of a stupendous lightning show. O'Neill's mental forecast was spot on.

Later, as we head back to Darwin in the car, he says: ‘That was a whole month's lightning in one night. I give it 20 out of 10.'

Firefront

Antarctic ice: Going, going …

Firefront

Ian Gibbins

The proposition
: a firefront, climbing the hillface, approaching lines of grey box,

an edge, a vibration, ragged, the juxtaposition of above and what lies below.

You must decide upon a frame of reference, a coordinate system, within which

local events, diary entries, arrivals and departures can be securely placed.

Option one
: (as usual) the sky. Some common descriptors: oppressive, leaden,

foreboding. Alternatively, overcast, cloud-streaked, ambivalent. And yet,

notwithstanding prior predictions, there is absolutely nothing to see: (as usual)

the air, through all its troughs and ridges, typical for the season, remains clear.

Option two
: the earth. Once again, far too familiar. You already
know what

it means: bedrock solid, unable to move without the application of heavy

machinery, set fast, interlocked to tectonic plates, a foundation stone, like

a mother's mother, off-white, like salt, or milk, or thoroughly unexpected snow.

Option three
: an ocean. How does it go? Roiling? Tumultuous? Surging with swell

and storm and eddy? Fathomless? Uncharted? The boundary we cannot extend?

A source of endless lies, stories that intrigue, inveigle, insist on continued disbelief.

Shallows tempting? Rising to cover your curling toes, your reefscarred shins.

Option four
: the fire itself. This you also know. The things that can burn: lava flows,

molten glass, cast iron, magnesium. Your throat, raw as it is. A blue-lined notebook,

school-yard friendship, fingertips, letters dreamt at midnight, music ringing from

plaster walls, a road you barely recognise. Objects singed and ashen and burst apart.

A final reminder
. To make a list. The items we must not forget. Ingredients we do not

grow here: cinnamon, clove, cardamon, Indian tea, black currant, berries, blueberries.

Materials we must find time to mine: cobalt, nickel, molybdenum, opal, fully

oxidised zinc, diamond, tourmaline, malachite, crystalline quartz, pure and simple.

The direction of the wind
. A return address. The passwords we require. The encryption

keys that preserve our integrity, hold our neighbours to account, plot a pathway out.

To repeat: the direction of the wind. Disentangle arms from safety blankets, scarlet

across our backs. What else? Count the numbers that name exploding supernovae.

Reached by committee, nineteen eighty-three

Liner notes,
Voyager
Golden Record

Antarctic ice: Going, going …

Nerilie Abram

It was January 2008 and I was on the back deck of HMS
Endurance
, wearing a full-body survival suit and eager for the short helicopter ride that would take me onto Antarctic ice for the first time. The ship was travelling through the channel that divides James Ross Island from the Antarctic Peninsula – a trip that would have been impossible not so long ago.

Since the 1990s, a series of ice shelves along the Antarctic Peninsula have collapsed, including the ice shelf that had once permanently connected James Ross Island to the rest of the continent. Most famously, the collapse of the nearby Larsen B ice shelf had been captured by satellite photographs. These images have been held up as an example of climate change happening before our eyes. But are they? This was what I was here to find out.

* * * * *

The Antarctic Peninsula is warming quickly. Over the last 50 years the climate here has warmed three times faster than the global average. The problem is that temperature measurements in this remote region don't go much further back than that. So how can we put the current warming into perspective?
The answer lies locked within Antarctica's ice. The ice blanketing most of the Antarctic continent is made of snow that has fallen and been buried. Scientists use these ancient ice layers as a window into Earth's past climate.

The deepest parts of Antarctica's great ice sheets might hold a climate record that goes back more than a million years. In the 2013–14 summer, scientists from the Australian Antarctic Division led an ice-drilling expedition to Aurora Basin, high on the East Antarctic plateau. This was part of a coordinated international effort towards the most ambitious and technically challenging piece of ice-core research ever attempted: the quest for Antarctica's ‘oldest ice'.

For the much smaller – and earlier – James Ross Island ice-drilling project, our team of seven scientists and engineers lived and worked in tents on the ice for almost two months. The top 283 metres of this ice cap consist of snow that's built up over the past thousand years. We know the age of the snow layers by counting the yearly summer-winter cycles of chemical impurities, such as sea salt, in the ice, and by the fixed time markers left in the snow by ash from volcanic eruptions.

To build a record of how temperature changed in the past, we measure the proportion of heavy versus light water molecules, or isotopes, in the ice. Isotopes are versions of the same element that have different numbers of neutrons, and so have different masses. In ice we measure the number of water molecules that have a heavy hydrogen atom (deuterium, with an atomic mass of 2) compared to those with the light hydrogen atom (atomic mass of 1). The heavy molecules take more energy to move through the water cycle, and in warm climates more of these heavy molecules will reach Antarctica and fall as snow. So the proportions of these molecules act as a ‘thermometer' for the past.

The isotopes in the James Ross Island ice core tell us the coolest time on the Antarctic Peninsula was around 600 years ago.
Back then the climate was around 1.6° Celsius cooler than today. The ice also confirms that the warming here since the 1920s has been exceptionally fast – faster than at almost any other time in the past thousand years.

But this particular ice core reveals much more about the changing climate on the Antarctic Peninsula. James Ross Island is a ‘Goldilocks' location for exploring the connection between temperature and ice melt. It is not so cold that summer temperatures are never high enough for melting to occur, and neither is it so warm that extensive melting destroys the climate record locked in the ice. Serendipitously, conditions on this ice cap are just right for preserving a rare history of summer ice melt.

The 1.6° Celsius of warming over the past 600 years may not sound significant, but it's caused a tenfold increase in the amount of summer melting on James Ross Island. Most of this intensification of ice melt occurred in the past few decades. This unique history of summer ice melt is a powerful illustration of how environmental changes in a warming climate don't always occur gradually.

Ice melt is an example of a threshold in Earth's environment. When summer temperatures remain below 0° Celsius, no melting occurs. But as the climate warms towards this threshold, on some days in summer the temperature will go above 0° Celsius and there will be excess energy to melt the surface snow. Any further warming will increase the number of days that go over the melting threshold, and increase the level by which they exceed it. In this way, a small increase in average temperature can cause a large increase in melting.

So are images like the Larsen B ice shelf collapse evidence for recent climate change? Measurements from the ice core say they are. It shows us that rising temperatures have taken summer ice melt on the Antarctic Peninsula to a level unprecedented for at least the past thousand years. Ice melt is a critical process that
weakens the structure of ice shelves and glaciers, and satellite images show that extensive summer melting caused the visually dramatic Larsen B collapse. Ice melt also has real implications for rising sea levels across the world.

* * * * *

Rising sea levels in a warming world are particularly relevant to Australia as large proportions of our population and infrastructure are near the coast.

In 2013, the IPCC released its fifth assessment report. On our current emissions trajectory it projects that sea level is likely to rise by between 0.53 and 0.97 metres by 2100. This projection takes into account the thermal expansion of the oceans as they warm, as well as changes in snowfall, surface melting and glacier loss that will alter the quantity of ice locked up on land. What these model-based projections aren't yet able to assess is the possibility of accelerating ice flow and loss from Antarctica's vast ice sheets.