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Are you ready for a four degree world?

Bush fires are just the start of the problems we’ll see in a world four degrees warmer. Sean Marshall/flickr

In mid-July, as Prime Minister Gillard began to stump the countryside selling her carbon package, a conference at the University of Melbourne considered the prospect of climate policy failure.

Climate scientists agree that the existing gap between climate science and climate policy is profound. If the international community – including Australia – merely meets its current emissions targets, we will see average global warming of around 4°C by the end of this century, and perhaps 6 to 8°C in centuries thereafter.

For three days, scientists, bureaucrats and members of the public examined the impacts of a four degree world on Australia’s environment, society and economy. It is the world of dramatic consequences that the carbon tax debate has so far neglected.

The transformations, both gradual and extreme, would be profound. Modelling by CSIRO indicates that, by 2100, average temperatures could increase by about 3°C to 5°C in coastal areas and 4°C to 6°C in inland areas.

There would be likely decreases in annual rainfall in southern Australia of up to about 50% but uncertain rainfall changes in other regions. Snow cover would fall to zero in most alpine regions.

Even small changes in mean global temperature will lead to dramatic changes in extreme weather events. But, as CSIRO scientist Kevin Hennessy suggests, “a warming of 4°C is likely to lead to increases in extremely high temperatures, extreme daily rainfall, extreme fire weather, large hail on the east coast, [increased] tropical cyclone intensity and extreme sea level events [storm surges]”.

As the Bureau of Meteorology’s Dr Karl Braganza explains, over time, in a changing climate system, what seem like record heat waves or rainfall events now will in the future seem normal, even mild.

What would this mean for Australia’s native plants and animals? Levels of endemicity are particularly high among Australia’s mammals, flowering plants, fish, reptiles, frogs and birds; this means many of them are only found here. Many of these endemic species have extremely narrow climatic and geographic ranges, predisposing them to risk from rapid environmental changes in the future.

Professor Lesley Hughes of Macquarie University reports that even relatively modest future warming of around 1°C will also have negative impacts on some ecosystems.

All these predictions are likely to be greatly exacerbated at 4°C warming and beyond, with climate change becoming an increasingly strong driver of local, and eventually global extinctions.

The impacts on marine life would be equally profound. At 4°C, the world’s oceans will be, according to Professor Ove Hoegh Guldberg, warmer, more acidic and less oxygenated – a state that has no analogue in the past 20-40 million years.

Sea level rise of up to about 1.1 metres by 2100 would likely increase to more than 7 metres over subsequent centuries. We would lose major ecosystems such as coral reefs and kelp forests, and see the disruption of present day fisheries and aquaculture by ocean warming and acidification.

These impacts have severe domestic economic consequences. For instance, the multi-billion dollar tourism and fisheries industries based around the iconic Great Barrier Reef would collapse. Similarly, Australian farming – which has learned to cope with extreme weather and a wide range of climatic regions – would be substantially transformed.

CSIRO’s Dr Mark Howden argues that projected weather changes across the major agricultural production zones would lead to a decline in production of core agricultural commodities. The area viable for growing crops will also change significantly.

Australia’s food surpluses will likely shrink and potentially become negative in some years and in some scenarios: certain Australian farm exports will be severely affected, as will domestic food security.

It is hard to know if we can adapt to these changes. As Professors Will Steffen and Dave Griggs emphasize, changes compound each other and are global, not just continental.

At 4°C, there is a significantly higher probability of tipping elements in the Earth system being activated, with reverberations around the world, including Australia. Examples include significant and rapid losses of ice from the Greenland and/or West Antarctic ice sheets and the conversion of the Amazon rainforest to savanna or grassland.

The reduction in the resilience of natural and managed ecosystems will affect the resilience of socio-economic systems in Australia and around the world. It will increase their vulnerability to other global non-climatic stressors and shocks, such as emerging pandemics, trade disruptions or financial market shocks. The state’s capacity to fund adaptation, mitigation and emergency measures – to rebuild cities and replace infrastructure – will be placed under increasing pressure.

ANU’s Professor Tony McMichael suggests that, as a result, living conditions for human populations, in Australia and elsewhere, would be surprisingly different from today. The environmental (and social) foundations of wellbeing, health and survival would have been progressively damaged.

Previous rapid temperature fluctuations of 3-5°C, historically, have caused great hardship, suffering, death and social-political disruption around the world.

Australia’s population health will face much more than frequent heat waves and weather disasters. There will be food shortages, malnutrition, increases in many infectious diseases (including epidemic outbreaks), widespread depression, anxiety and rural misery, and tensions and conflicts over resource shortages, population displacement and refugee flows.

It is also hard to assess the implications for regional security, but drought and food shortages would cause displacement of up to 250 million people across West Asia, South Asia, South-East Asia and Indonesia by the end of this century.

Sea-level rise and storm water intrusion would cause further massive dislocation of coastal communities, the abandonment of coastal cities, and severe economic disruption in China, Bangladesh and Indonesia. The abandonment of uninhabitable low-lying islands in the Pacific would create displace whole national populations.

At one point during his keynote speech, Professor Hans Joachim Schellnhuber, Director of the Potsdam Institute for Climate Impact Research and former climate adviser to the German Chancellor and the EU, asks rhetorically: “What is the difference between two degrees (of temperature increase) and four degrees?”

“The difference,” he said, “is human civilisation”.

The explicit message of this conference, then, is that we need to cut greenhouse emissions urgently. As the Climate Commission has said, this is the Critical Decade for action.

In 2007 the IPCC indicated developed countries should reduce their collective emissions by between 25-40% below 1990 levels by 2020, to help stay below 2°C warming. That was before recent emissions data showed that we are tracking at above the IPCC’s most pessimistic projections, suggesting that cuts at the top end of this range are now required.

Australia is the world’s 10th biggest aggregate emitter. We have the world’s highest per capita emissions. We are one of the world’s most affluent countries. Yet Australia’s short term target of -5% below 2000 levels by 2020 is among the weakest of all industrialised and major industrialising nations. If adopted by all industrialised countries, our target would see global average temperatures rise by more than 4°C by 2100.

Our effort is neither fair nor equal when measured against that of other comparably wealthy industrialised countries like the United Kingdom (which has cut emissions by 23% and aiming to halve them below 1990 levels by 2025) or even the efforts of China and Brazil.

In this larger context, the modest and politically astute start to decarbonising our economy is a critical first step. But if it fails to gather pace quickly, the heavy price of a soft start – as the ‘Four Degrees’ conference outlined - will be paid for by our children and by future generations.

Conference presentations are available at:

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