Antarctic ice shows Australia’s drought and flood risk is worse than thought

Anthony Kiem, University of Newcastle; Carly Tozer, University of Newcastle, and Tessa Vance, University of Tasmania

Australia is systematically underestimating its drought and flood risk because weather records do not capture the full extent of rainfall variability, according to our new research.

Our study, published today in the journal Hydrology and Earth System Sciences, uses Antarctic ice core data to reconstruct rainfall for the past 1,000 years for catchments in eastern Australia.

The results show that instrumental rainfall records – available for the past 100 years at best, depending on location – do not represent the full range of abnormally wet and dry periods that have occurred over the centuries.

In other words, significantly longer and more frequent wet and dry periods were experienced in the pre-instrumental period (that is, before the 20th century) compared with the period over which records have been kept.

Reconstructing prehistoric rainfall

There is no direct indicator of rainfall patterns for Australia before weather observations began. But, strange as it may sound, there is a link between eastern Australian rainfall and the summer deposition of sea salt in Antarctic ice. This allowed us to deduce rainfall levels by studying ice cores drilled from Law Dome, a small coastal ice cap in East Antarctica.

It might sound strange, but there’s a direct link between Antarctic ice and Australia’s rainfall patterns.
Tas van Ommen, Author provided

How can sea salt deposits in an Antarctic ice core possibly be related to rainfall thousands of kilometres away in Australia? It is because the processes associated with rainfall variability in eastern Australia – such as the El Niño/Southern Oscillation (ENSO), as well as other ocean cycles like the Interdecadal Pacific Oscillation (IPO) and the Southern Annular Mode (SAM) – are also responsible for variations in the wind and circulation patterns that cause sea salt to be deposited in East Antarctica (as outlined in our previous research).

By studying an ice record spanning 1,013 years, our results reveal a clear story of wetter wet periods and drier dry periods than is evident in Australia’s much shorter instrumental weather record.

For example, in the Williams River catchment, which provides water for the Newcastle region of New South Wales, our results showed that the longest dry periods lasted up to 12 years. In contrast, the longest dry spell since 1900 lasted just eight years.

Among wet periods, the difference was even more pronounced. The longest unusually wet spell in our ice record lasted 39 years – almost five times longer than the post-1900 maximum of eight years.

Busting myths about drought and flood risk

Although this does not tell us when the next major wet or dry period will happen, it does help us predict how often we can expect such events to occur, and how long they might last. This is critical information for water resource managers and planners, especially when our millennium-long record tells a very different story to the post-1900 instrumental record on which all water infrastructure, planning and policy is based.

Our results challenge the underlying assumptions that govern water resource management and infrastructure planning. These assumptions include:

  • that droughts longer than five years are rare;

  • that droughts or flood-dominated periods cannot last longer than about 15 years;

  • that drought and flood risk does not change over time, so a century of instrumental records is enough to gain a full understanding of the situation.

The fact that these assumptions are probably wrong is a concern. These principles are used to make crucial decisions, not just about predicting the likelihood and severity of droughts and floods themselves, but also about the design of infrastructure such as roads, reservoirs and buildings. Our study suggests that these decisions are being taken on the basis of incomplete information.

Cold case: drilling for ice to reveal long-term weather patterns.
Tessa Vance, Author provided

What’s more, Australia’s increasing population and development will mean that water demands and exposure to droughts and floods are likely to have been different in the past to what they are now (and will be in the future).

Therefore, given that the factors used to quantify risk are most likely wrong, it implies that current hydroclimatic risk assessments are not representative of the true level of risk.

This raises serious questions about water security and the robustness of existing water resource management, infrastructure design and catchment planning across eastern Australia and in other places where hydroclimatic risk is assessed on records that do not capture the full range of possible variation.

Water is a precious resource, meaning that we need the best knowledge about what our rainfall patterns are capable of delivering. Our findings can be used to better characterise and manage existing and future flood and drought risk. Forewarned is forearmed.

The Conversation

Anthony Kiem, Senior Lecturer – Hydroclimatology, University of Newcastle; Carly Tozer, Hydrologist, Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, University of Newcastle, and Tessa Vance, Palaeoclimatologist, Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania

This article was originally published on The Conversation. Read the original article.


Why we need environmental accounts alongside national accounts

Michael Vardon, Australian National University and Peter Burnett, Australian National University

The Federal Budget has been delivered and Australians are headed for the polls. In this series, Reform Revisited, we ask writers for innovative ways to tackle our reform agenda.

Charles Dickens’ character Oliver Twist is perhaps best known as the boy who wanted more. Of course, he got none. Instead, his efforts prompted Mr Bumble, the parish beadle (official) to offer a princely £5 to anyone who would take the boy off his hands.

The environment is something of a modern Oliver Twist in the budget workhouse. There’s certainly no more porridge on offer – indeed significantly less counting the changes to renewable energy funding announced on 23 March. Last Tuesday’s federal budget contained no new policy and no new money, only some savings and the allocation of funds already set aside for environmental purposes. And, Mr Bumble-like, the Government remains committed to its “one-stop shop” policy of transferring environmental approval powers to “willing jurisdictions”, to use the terminology of the Department of Environment.

But how much budget porridge is needed for a hungry environment? And what does the environment do that deserves porridge anyway? The budget might at least be expected to consider the environment’s contribution to the economy (for example, through agriculture) if not in relation to the broader goal of maintaining the environment for its inherent value, as articulated by Environment Minister Greg Hunt’s budget media release.

The budget continues to support some worthy initiatives, such as the management and protection of the Great Barrier Reef through the Reef 2050 Plan. But, overall, we do not know if the budget funding will deliver the desired results across the environment, to maintain the functions that support our economy and lifestyle. Compare this the comprehensive information and accounting systems in place to measure the performance and contribution of different industries (agriculture, manufacturing, retail trade and education) in the economy.

The deficiency could be remedied by making better use of data – both scientific and economic. The economic part of the budget is well served with information and forecasts of economic conditions, but the environmental part is not, despite the increasing availability of environmental information, not only from established sources such as the five-yearly State of the Environment Report, rainfall and temperature outlooks from the Bureau of Meteorology, but from new sources, such as the recently released Australia’s Environment in 2015 which is the latest example of distilling the increasingly large amount information available from remote sensing technology.

None of this is factored into the Budget in the way that economic indicators such as unemployment or economic growth rates are, so the impacts and risks of the changing environment on the economy are ignored.

These days, the problem is more one of data organisation rather than data availability. The obscurely-titled System of Environmental-Economic Accounting (SEEA) attempts to do for the environment what the System of National Accounts has done for the general economy: systematically and regularly present data in a way that reveals what is going on, and to some extent, why.

The ABS already uses SEEA to produce accounts, although these are as yet very basic. If Treasury used information from a comprehensive set of environmental accounts alongside its existing information in developing the Budget, the economic and environmental justifications for environmental spending would be much clearer. More fundamentally, we would have a much better sense of whether we were on the path to sustainability, and if not, where additional investment could have most impact.

Oliver Twist was of course fiction. But in penning his novel Dickens had a real-world target: the British Poor Law Amendment Act of 1834, which ushered in a primitive work-for-the-dole scheme in the form of parish workhouses. While the immediate problem in the story might have been Oliver’s empty bowl, the underlying problem in the real world was that with the industrial revolution, the parish system on which British society had operated for centuries was breaking down rapidly as rural workers migrated en masse to the newly-industrialised cities. Forcing the indigent into workhouses was a budget fix, when what was really needed was a new welfare system.

The approaches taken in managing Australia’s environment, including through the Budget, are as obsolete as the Poor Law was in Dickensian Britain. We don’t know how much environmental investment is needed, or where best to place it. But just as the Turnbull government has a 10-year economic plan for reducing company tax, and is making a 40-year investment in submarines, we need a long-term plan for environmental investment. Until we have a comprehensive set of environmental accounts linked to existing economic information, such a plan will lack foundation and our modern Oliver Twist will have no option beyond the poorhouse plea: “Please, sir, I want some more.”

Read more in the series here.

The Conversation

Michael Vardon, Visiting Fellow at the Fenner School, Australian National University and Peter Burnett, PhD Candidate, Australian National University

This article was originally published on The Conversation. Read the original article.