As drought looms, the Murray-Darling is in much healthier shape – just don’t get complacent

James Horne, Australian National University

Melbourne Cup Day is a significant day in the history of water policy in Australia. The first Tuesday in November 2006 saw the then Prime Minister John Howard intervene decisively in the growing drought crisis in the southern Murray-Darling Basin (MDB).

Nine years on, the spectre of drought is back. The Murray Darling Basin Authority’s weekly reports show inflows into the River Murray (which can be seen as a proxy for the southern MDB) during the year to end September 2015 were the among the lowest on record. And the Bureau of Meteorology’s National Climate and Water Briefing last week suggests a warm and dry summer in prospect in the southern MDB, amid a still strengthening El Niño.

Yet there are reasons to believe that these past nine years of stronger Commonwealth involvement have left the MDB much better placed to withstand an escalating drought.

That said, there is no room for complacency, and continuing Commonwealth commitment is still needed if those hard-won gains are to be retained.

Turning the tide

Thanks to the Water Act 2007 and the Basin Plan 2012, we now have much deeper understanding of the MBD’s water resources, as well as better governance and planning.

For decades, more and more water was being diverted away from the basin’s rivers and extracted from its aquifers. The Howard government’s leadership, and the subsequent Labor governments’ maintenance of these plans, helped to put the brakes on that by creating a large Commonwealth portfolio of “environmental water” which has been purchased from irrigators.

Over the past four years nearly 4,000 gigalitres (about eight Sydney Harbours) of Commonwealth environmental water have been delivered to different parts of the MDB. This has kept the River Murray’s mouth open for longer, ensuring more disposal of salt out to sea, and has helped to partly restore the Lower Lakes and Coorong after the last drought.

This means that, with another drought in prospect, the environment has at least had a chance to take a breath and partially recover, and that some environmental water will still be available over the coming year.

Water markets have now also become fully operational, making it easier for irrigators and other water users (including the environment) to manage their valuable water entitlements, and to trade these entitlements if necessary.

Meanwhile, billions of dollars have been invested in modernising irrigation infrastructure in the MDB to help irrigators use water more efficiently in the future, and funds have been made available to help landowners rationalise unproductive and inefficient irrigation infrastructure. The next drought will help us assess how successful this has been.

Hopefully we won’t let it get into this state again.
AAP Image/Larine Statham

The flow of information about the MDB has improved, too. The Bureau of Meteorology now provides better, more timely information to all river operators, water users and policy makers around Australia. Up-to-date storage data and accurate forecasts of rainfall and streamflow help irrigators make better business decisions. It is critical that the investments be sustained in coming years.

The Basin Plan also provides assurance for communities that depend on the River Murray system for their human water needs. Under the plan, if critical water shortages emerge, these communities will be given the highest priority. Adelaide’s new desalination plant (arguably far larger than needed!) will further bolster the city’s water security, as it can deliver more than three-quarters of demand. And Canberra’s Cotter Dam upgrade can store the equivalent of more than a year’s water demand.

Still more to do

The Basin Plan requires states to put in place 36 compliant regional water resource plans in the MDB. These are long overdue – much progress has been made in the past nine years, but the states need to ensure that this project is completed as soon as possible.

Water extractions limits (called sustainable diversion limits) will need to be reduced to ensure that they are sustainable even before climate is considered, but this measure has already been delayed until 2019 as a part of a deal with the states to make the Basin Plan.

Full action on climate change in the basin has also been put off until 2022. This will need to be reassessed as a matter of urgency once 2022 rolls around.

The Commonwealth now plays a far more significant and effective role than it did nine years ago, and is now very much a partner in managing the MDB as a whole, along with the states and basin communities. As Parliamentary Secretary for Water at the time nine years ago, our new Prime Minister Malcolm Turnbull well understands how quickly the water outlook in the southern MDB can deteriorate (see chart below).

Water levels for Hume and Dartmouth
Bureau of Meteorology

The Murray-Darling Basin has much more of a safety net today than it did in November 2006, so we are not facing crisis. But there is no room for complacency – effectively caring for our scarce water resources continues to be essential, and it needs to be done on a basin-wide basis rather than with the interests of a particular state or industry in mind.

But hopefully, what began in earnest almost a decade ago can be a continuing example of how to look after a regional economy, communities and the environment.

James Horne, Visiting Fellow in public policy/water, Australian National University

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

Melting Antarctic ice sheets and sea level rise: a warning from the future

Andrew Glikson, Australian National University

The remote location of the Antarctic and Greenland polar ice sheets may leave us with the impression that developments in these regions have little effect on the climate and life in the temperate zones of the Earth, where most of us live. We may therefore be forgiven for asking why should we care when these changes are projected to unfold over tens to hundreds of years.

However, the stability of the polar regions is critical for maintaining a planet with the conditions that allowed the emergence of humans, agriculture and civilisation, as well as many other species. The polar ice sheets serve as “thermostats” of global temperatures from which cold air and cold ocean currents emanate, moderating the effects of solar radiation. The ice sheets regulate sea levels, store volumes of ice whose melting would raise sea level by up to 61 metres.

Unfortunately, what’s happening with the polar ice sheets now ought to warn humanity of what is to come.

For example, a recent paper suggested that melting Antarctic ice sheets could lead to 0.6-3.0 m of sea level rise by the year 2300. This is based on modelling of greenhouse gas emissions out to 2300.

If greenhouse gas emissions continue unchecked, the world may warm by 8–10℃ by 2300. Such a temperature rise could raise sea levels by tens of meters over hundreds of years.

The recent paper only looked at sea level rise from melting Antarctic ice sheets and does not take into account sea level rise contributions from the Greenland ice sheet (currently about 280 billion tonnes per year), which would more than double the Antarctic contribution.

Antarctic warming: Red represents areas where temperatures have increased the most during the last 50 years, particularly in West Antarctica.
NASA

Peering into the past to see the future

Much of the discussion in the paper and related papers appears to assume linear global warming – that is, little change to the rate of warming over time.

Little mention is made of feedbacks which could increase the rate of warming. Such feedbacks could arise from reducing albedo, where solar radiation usually strongly reflected by ice is replaced by strong absorption by water.

Other feedback processes associated with warming include methane release from permafrost and bogs; loss of vegetation; and fires.

In a recent article, former NASA climate scientist James Hansen and a large group of climate scientists point to observations arising from detailed studies of the recent history of the atmosphere-ocean-ice sheet system.

The climate records of the past — specifically, the Holocene (from about 10,000 years ago) and the Eemian interglacial period (about 115,000 to 130,000 years ago) — are closely relevant to future climate projections. These records include evidence for rapid disintegration of ice sheets in contact with the oceans as a result of feedback processes resulting in sea level rise to 5-9 m above current levels. All this during a period when mean global temperatures were near to only 1℃ above pre-industrial temperatures.

Sea levels reflect the overall global temperature and thus of global climate conditions. As shown by the position of the circles in the chart below, the ratio of sea level rise (SL) to temperature rise (TR) during the glacial-interglacial cycles was approximately between 10-15 metres per 1℃.

Plots of Temperature rise (relative to the pre-industrial age) vs relative sea level rise in (meters).

By contrast from around 1800 to the present sea level rose by an approximate ratio of 0.2-0.3 m per 1℃. This suggests significant further rise towards an equilibrium state between sea level and temperature. Thus, the points in the right-hand circle represent long-term temprature-sea level equilibria in the past while points in the left-hand circle represent where we’re at now, namely at an incipient stage moving toward future temprature-sea level equilibrium.

Why should long term climate change matter?

Due to the extreme rate of CO₂ and temperature rise during the 20th century relative to earlier events and the non-linearity of climate change trends the timing of sea level rise may be difficult to estimate.

Even on conservative estimates, current global warming is bound to have major consequences for human civilisation and for nature, as follows:

Further melting of the ice sheets will destroy the climate conditions which allowed agriculture and the rise of civilisation in the first place.
The lower parts of the world’s great rivers (Po, Rhine, Nile, Ganges, Indus, Mekong, Yellow, Mississippi, Amazon), where more than 3 billion people live and the bulk of agriculture and industry are located, sit no more than a few metres above sea level.
Further melting of the Antarctic and Greenland ice sheets can only result in sea level rises on the scale of tens of metres, changing the continent-ocean map of Earth.

Global temperatures have already risen 0.9℃ and continental temperatures 1.5℃ degrees above pre-industrial levels. If we account for the cooling effect of sulphur aerosols from industrial pollution, greenhouse gases have already contributed 2℃ of global warming. The current rate of global warming, faster than any observed in the geological record, is already having a major effect in many parts of the world in terms of droughts, fires, and storms.

According to James Hansen burning all the fossil fuels on Earth would result in warming of 20℃ over land areas and a staggering 30℃ at the poles, making “most of the planet uninhabitable by humans”.

In 2009 Joachim Hans Schellnhuber, Director of the Potsdam Climate Impacts Institute and Climate Advisor to the German Government, stated: “We’re simply talking about the very life support system of this planet”, constituting one of the most critical warnings science has ever issued to our species.

Mitigation plans proposed by governments would slow down the rate of carbon emissions but continuing emissions as well as feedbacks from ice melt, warming oceans, methane release and fires would continue to push temperatures upwards.

An effective technology required for global cooling efforts, if technically possible, would require investment on a scale not less than the trillions of dollars currently poured into armaments and war in the name of defence (more than $1.6 trillion in 2014).

Which planet do current decision makers think we are living on?

Andrew Glikson, Earth and paleo-climate scientist, Australian National University

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