The Sydney Barrier Reef: engineering a natural defence against future storms


Rob Roggema, University of Technology Sydney

The risk of more severe storms and cyclones in the highly urbanised coastal areas of Newcastle, Sydney and Wollongong might not be acute, but it is a real future threat with the further warming of the southern Pacific Ocean. One day a major storm – whether an East Coast Low or even a cyclone – could hit Sydney. The Conversation

With higher ocean temperatures killing and bleaching coral along the Great Barrier Reef to the north, we could also imagine where the right temperatures for a coral reef would be in a warmer climate. Most probably, this would be closer to the limits of the low latitudes, hence in front of the Sydney metro area.

We should then consider whether it is possible to help engineer a natural defence against storms, a barrier reef, should warming oceans make conditions suitable here.

Ocean warming trend is clear

The oceans are clearly warming at an alarming rate, with the unprecedented extent and intensity of coral bleaching events a marker of rising temperatures. After the 2016-2017 summer, coral bleaching affected two-thirds of the Great Barrier Reef.

On the other side of the Pacific, sea surface temperatures off Peru’s northern coast have risen 5-6℃ degrees above normal. Beneath the ocean surface, the warming trend is consistent too.

The East Australian Current keeps the waters around Lord Howe Island warm enough to sustain Australia’s southernmost coral reef. The waters off Sydney are just a degree or two cooler.

With the East Australian Current now extending further south, the warming of these south-eastern coastal waters might be enough in a couple of decades for Nemo to swim in reality under Sydney Harbour Bridge.

This shift in ocean temperatures is expected to drive strong storms and inland floods, according to meteorologists.

On top of this, when we plot a series of maps since 1997 of cyclone tracks across the Pacific, it shows a slight shift to more southern routes. These cyclones occur only in the Tasman Sea and way out from the coast, but, still, there is a tendency to move further south. The northern part of New Zealand recently experienced the impacts this could have.

Think big to prepare for a big storm

If we would like to prevent what Sandy did to New York, we need to think big.

If we don’t want a storm surge entering Parramatta River, flooding the low-lying areas along the peninsulas, if we don’t want flash-flooding events as result of river discharges, if we don’t want our beaches to be washed away, if we want to keep our property along the water, and if we want to save lives, we’d better prepare to counter these potential events through anticipating their occurrence.

The coast is the first point where a storm impacts the city. Building higher and stronger dams have proven to be counterproductive. Once the dam breaks or overflows the damage is huge. Instead we should use the self-regenerating defensive powers nature offers us.

Thinking big, we could design a “Sydney Barrier Reef”, which allows nature to regenerate and create a strong and valuable coast.

The first 30-40 kilometres of the Pacific plateau is shallow enough to establish an artificial reef. The foundations of this new Sydney Barrier Reef could consist of a series of concrete, iron or wooden structures, placed on the continental shelf, just beneath the water surface. Intelligently composed to allow the ocean to bring plants, fish and sand to attach to those structures, it would then start to grow as the base for new coral.

This idea has not been tested for the Sydney continental flat yet. But in other parts of the world experiments with artificial reefs seem promising. At various sites, ships, metro carriages and trains seem to be working as the basis for marine life to create a new underworld habitat

The Sydney Barrier Reef will have the following advantages:

  1. Over decades a natural reef will grow. Coral will develop and a new ecosystem will emerge.

  2. This reef will protect the coast and create new sandbanks, shallow areas and eventually barrier islands, as the Great Barrier Reef has done.

  3. It will increase the beach area, because the conditions behind the reef will allow sediments to settle.

  4. It creates new surfing conditions as a result of the sandbanks.

  5. It will protect Sydney from the most severe storm surges as it breaks the surge.

  6. It will present a new tourist attraction of international allure.

Let’s create a pilot project as a test. Let’s start to design and model the pilot to investigate what happens in this particular location. Let’s simulate the increase of temperature over time and model the impact of a cyclone.

Let’s create, so when Sandy hits Sydney, we will be better protected.

Rob Roggema, Professor of Sustainable Urban Environments, University of Technology Sydney

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

Was Tasmania’s summer of fires and floods a glimpse of its climate future?


Alistair Hobday, CSIRO; Eric Oliver, University of Tasmania; Jan McDonald, University of Tasmania, and Michael Grose, CSIRO

Drought, fires, floods, marine heatwaves – Tasmania has had a tough time this summer. These events damaged its natural environment, including world heritage forests and alpine areas, and affected homes, businesses and energy security.

In past decades, climate-related warming of Tasmania’s land and ocean environments has seen dozens of marine species moving south, contributed to dieback in several tree species, and encouraged businesses and people from mainland Australia to relocate. These slow changes don’t generate a lot of attention, but this summer’s events have made people sit up and take notice.

If climate change will produce conditions that we have never seen before, did Tasmania just get a glimpse of this future?

Hot summer

After the coldest winter in half a century, Tasmania experienced a warm and very dry spring in 2015, including a record dry October. During this time there was a strong El Niño event in the Pacific Ocean and a positive Indian Ocean Dipole event, both of which influence Tasmania’s climate.

The dry spring was followed by Tasmania’s warmest summer since records began in 1910, with temperatures 1.78℃ above the long-term average. Many regions, especially the west coast, stayed dry during the summer – a pattern consistent with climate projections. The dry spring and summer led to a reduction in available water, including a reduction of inflows into reservoirs.

Left: September-November 2015 rainfall, relative to the long-term average. Right: December 2015-February 2016 temperatures, relative to the long-term average.
Bureau of Meteorology, Author provided

Is warmer better? Not with fires and floods

Tourists and locals alike enjoyed the clear, warm days – but these conditions came at a cost, priming Tasmania for damaging bushfires. Three big lightning storms struck, including one on January 13 that delivered almost 2,000 lightning strikes and sparked many fires, particularly in the state’s northwest.

By the end of February, more than 300 fires had burned more than 120,000 hectares, including more than 1% of Tasmania’s World Heritage Area – alpine areas that had not burnt since the end of the last ice age some 8,000 years ago. Their fire-sensitive cushion plants and endemic pine forests are unlikely to recover, due to the loss of peat and soils.

Meanwhile, the state’s emergency resources were further stretched by heavy rain at the end of January. This caused flash flooding in several east coast towns, some of which received their highest rainfall ever. Launceston experienced its second-wettest day on record, while Gray recorded 221 mm in one day, and 489 mm over four days.

Flooding and road closures isolated parts of the state for several days, and many businesses (particularly tourism) suffered weeks of disruption. The extreme rainfall was caused by an intense low-pressure system – the Climate Futures for Tasmania project has predicted that this kind of event will become more frequent in the state’s northeast under a warming climate.

Warm seas

This summer, an extended marine heatwave also developed off eastern Tasmania. Temperatures were 4.4℃ above average, partly due to the warm East Australian Current extending southwards. The heatwave began on December 3, 2015, and was ongoing as of April 17 – the longest such event recorded in Tasmania since satellite records began in 1982. It began just days after the end of the second-longest marine heatwave on record, from August 31 to November 28, 2015, although that event was less intense.

Anatomy of a marine heatwave. Top left: summer sea surface temperatures relative to seasonal average. Top right: ocean temperature over time; red shaded region shows the ongoing heatwave. Bottom panels: duration (left) and intensity (right) of all recorded heatwaves; the ongoing event is shown in red.
Eric Oliver

As well as months of near-constant heat stress, oyster farms along the east coast were devastated by a new disease, Pacific Oyster Mortality Syndrome, which killed 100% of juvenile oysters at some farms. The disease, which has previously affected New South Wales oyster farms, is thought to be linked to unusually warm water temperatures, although this is not yet proven.

Compounding the damage

Tasmania is often seen as having a mild climate that is less vulnerable to damage from climate change. It has even been portrayed as a “climate refuge”. But if this summer was a taste of things to come, Tasmania may be less resilient than many have believed.

The spring and summer weather also hit Tasmania’s hydroelectric dams, which were already run down during the short-lived carbon price as Tasmania sold clean renewable power to the mainland. Dam levels are at an all-time low and continue to fall.

The situation has escalated into a looming energy crisis, because the state’s connection to the national electricity grid – the Basslink cable – has not been operational since late December. The state faces the prospect of meeting winter energy demand by running 200 leased diesel generators, at a cost of A$43 million and making major carbon emissions that can only exacerbate the climate-related problems that are already stretching the state’s emergency response capability.

Is this summer’s experience a window on the future? Further study into the causes of climate events, known as “detection and attribution”, can help us untangle the human influence from natural factors.

If we do see the fingerprint of human influence on this summer, Tasmania and every other state and territory should take in the view and plan accordingly. The likely concurrence of multiple events in the future – such as Tasmania’s simultaneous fires and floods at either end of the island and a heatwave offshore – demands that governments and communities devise new strategies and mobilise extra resources.

This will require unprecedented coordination and cooperation between governments at all levels, and between governments, citizens, and community and business groups. Done well, the island state could show other parts of Australia how to prepare for a future with no precedent.

The Conversation

Alistair Hobday, Senior Principal Research Scientist – Oceans and Atmosphere, CSIRO; Eric Oliver, Postdoctoral Fellow (Physical Oceanography and Climate), University of Tasmania; Jan McDonald, Professor of Environmental Law, University of Tasmania, and Michael Grose, Climate Projections Scientist, CSIRO

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

19th century weather data is helping climate scientists predict the future


Linden Ashcroft, Universitat Rovira i Virgili; Howard Bridgman, University of Newcastle, and Ken Thornton, University of Newcastle

The 19th-century English historian Lord Acton famously advised people to live in both the future and the past, and said “those who do not live in the past cannot live in the future”.

It may seem a stretch to apply this famous quotation to climate research, but we can’t possibly understand how the climate will change in the future without first understanding how it changed in the past.

Australia’s official climate record, kept by the Bureau of Meteorology, begins in 1910. But historical climate records kept before the development of national meteorological organisations are valuable tools for improving our understanding of what has happened in the past.

They also put the present into a long-term context, and improve climate models used to predict the future.

What can old numbers really tell us?

One thing historical records can help us understand is extreme weather events – the aspect of climate change that has people most concerned. How can we prepare cities and buildings for storms in the future without understanding what previous storms have done?

It is true that historical observations have reliability issues and are sometimes hard to compare to modern observations, which are recorded in a standard way. However, old weather records can still tell us a lot about year-to-year changes, and there are many ways to minimise reliability problems.

There are several climate and weather analysis products that recreate how the atmosphere behaved over time. In the Southern Hemisphere, these climate tools are generally uncertain until the mid-20th century, due to a lack of – you guessed it — long-term data.

Historical records can also help us hone climate models for predicting the future. Some of the atmospheric and oceanic features that dominate our climate have cycles that can last several decades. This means that modern climate data starting in the 20th century may only capture one or two cycles of a particular feature, making it hard to train climate models on the full range of our climate variability.

Historical weather records are also important for past climate analysis. Extracting the climate signal from tree rings, ice cores, or documentary data, requires instrumental climate records for comparison. The longer the climate records are, the better this comparison will be.

What exists for Australia?

In the past few years, concerted efforts at the Bureau of Meteorology and several universities have been able to recover and analyse a large amount of historical climate data for Australia. Most of these observations come from Australia’s southeast, as this is the region that was first colonised by Europeans.

There are now studies that explore temperature, rainfall and atmospheric pressure variability in southeastern Australia back to the 1860s. Several studies have even rescued data from 1788.

With these newly recovered observations, we have learned a lot about Australia’s climate in the 19th century, as well as the early years of English colonisation. But there is still a lot we don’t know.

In particular, the majority of our old weather data come from coastal locations, where the weather is more sensitive to local factors rather than large-scale features such as the El Niño–Southern Oscillation (ENSO).

A rare opportunity

In 2011, some weather diaries were donated to the University of Newcastle and University of New England. The diaries contain 45 years of daily handwritten weather observations of a Mr Algernon Belfield taken on his 8,000-hectare property, Eversleigh, near Armidale in northern New South Wales.

A H Belfield at Eversleigh
Belfield Family

A pastoralist, amateur meteorologist and astronomer, Belfield took these meticulous weather observations every morning at 9am from June 1877 until August 1922, a month before his death.

His observations continued through the period of the 1891 shearers’ strike, the Boer War, Australia’s Federation, the First World War and the Centennial and Federation droughts.

Belfield’s diaries also span the period that inspired Dorothea Mackellar’s famous ode to Australia, My Country.

The last few decades of the 19th century were indeed times of “droughts and flooding rains”, thanks to a string of La Niña and El Niño phases of ENSO.

Belfield weather diaries
Ken Thornton (Author)

Belfield’s steady hand captured the weather at Eversleigh during a time of dramatic variability before the impact of human-induced climate change, in a region where the climate is highly correlated with ENSO.

His detailed records, therefore, provide us with a unique opportunity to uncover more about this period in our climate history than ever before.

The handwritten records are scanned but need to be transcribed into a digitised format. We are looking for volunteers to help us with this important task of recovering our climate history. If you are interested, please contact us here, to help shed light on Australia’s past, present and future climate.

The Conversation

Linden Ashcroft, Senior Researcher, Universitat Rovira i Virgili; Howard Bridgman, Conjoint Professor, University of Newcastle, and Ken Thornton, Affiliate, Cultural Collections, University of Newcastle

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

After Paris, the future of Australian coal is downhill


Gary Ellem, University of Newcastle

The ink is barely dry on the Paris climate agreement and the debate has already started on how the deal will affect the future of fossil fuels, particularly coal.

Following the deal on Sunday, the mining industry has responded that Australian coal will remain an important provider of affordable energy to developing countries. The industry argues new low emissions technologies will keep coal in business as the world cuts carbon.

Foreign minister Julie Bishop echoed the sentiment in Paris last week, stating “coal-fired power generation is here to stay.”

The agreement aims to limit global temperature rise to less than 2℃, with an aspiration of 1.5℃. So what is the future of coal in a world that meets these temperature limits?

Who’s going to build the new coal infrastructure?

Keeping warming “well below 2℃ above preindustrial levels and pursuing efforts to limit the temperature increase to 1.5℃” essentially means all new electricity generation from now on must be zero emissions or have a short amortisation life. Current emissions-intensive generation will also have to be phased out in line with the end of its initial design life.

Most coal in Australia is mined to be exported. For Australian coal exports to continue to play a significant role in our balance of trade, we must have international customers.

Australia produces both thermal coal for electricity and metallurgical coal for manufacturing, which is exported mainly to countries in Asia. Some of these customers, such as China and India, have their own coal production sectors, which produce significantly more coal than Australia. Others, such as Japan, are completely import dependent.

Whichever way the coal is used, it will add to the amount of greenhouse gases in the atmosphere unless these emission are captured by carbon capture and storage (CCS) technologies.

The infrastructure that will power our international customers’ electricity grids, steel and cement plants in 2050 largely hasn’t been built yet. In a less than 2℃ world, all of this infrastructure will have to be close to zero emissions. In a 1.5℃ world, any remaining emissions will have to be offset.

This means that if our customers decide to stay with coal, they will have to replace their existing infrastructure with new infrastructure incorporating carbon capture and storage, and even further offset emissions for a 1.5℃ future with the use of biomass.

It’s clear that China has already opted for an anything but coal policy. The policy future for India is not so clear, but they are clearly planning to be more self sufficient in coal production regardless of climate objectives. Neither of these look good for the future of Australian coal exports in either the short or long term.

The competition is heating up

The Australian coal export sector is threatened by both the rise of competing technologies and other suppliers.

Competing technologies in the electricity generation space are numerous and include nuclear as well as a swathe of renewable energy technologies that are becoming cheaper and more practical.

It’s clear that carbon capture and storage technologies have failed in the current competition environment as a cheap alternative to the other low and zero-emissions technologies such as renewables. Coal has rapidly ceded ground to gas, wind, hydro and solar in key markets such as the US and China.

The long-term outlook for coal for electricity then, is shaky at best. Australia is competing for market share in a shrinking market. The International Energy Agency report quoted by the Minerals Council for a rosy coal future is very clear that the modelling is based on the continuation of pre-Paris trends rather than the Paris agreement.

Even the well-trodden claims that intermittent renewables can’t supply the baseload power normally supplied by coal are looking flaky. Energy storage in the form of batteries in particular is rapidly getting cheaper and building in production capacity. A number of different battery types including lithium ion, sodium ion, aluminium ion and liquid metal batteries are all in development with on grid storage markets in mind.

The outlook for metallurgical coal may be more promising, simply because there are fewer technologies to compete.

Coal is used predominantly in blast furnaces to convert iron ore into metallic iron. Blast furnaces use coking coal to hold iron ore in place, while cheaper Pulverised Coal Injection (or PCI) coal is used to remove oxygen from the iron.

PCI coal can be replaced by charcoal from plants, reducing emissions by 18% to 40%. But there’s no current replacement for coking coal used in a blast furnace.

The Hismelt process from Rio Tinto can convert iron ore to new iron without the need for coking coal. But this technology is in its commercial infancy.

Should we rely on the Australian coal industry?

The coal industry has played an important role in the development of Australia as a modern industrialised economy. It has formed the basis for energy security in the Australian electricity sector and our domestic steel sector.

In more recent times, coal has been a major export commodity for Australia and has also powered the export-focused aluminium sector. Despite all of these great achievements, it’s hard to see a long-term positive future for the industry in a global marketplace looking for competitive solutions to their 2℃ and 1.5℃ needs.

Innovation is borne of constraint however, and it will be good for all of us if carbon capture and storage could be made cheap enough and deployable enough for widespread use. There are reasons for pursuing this technology besides coal. Carbon capture and storage can be combined with bioenergy in the form of BECCS to develop one of the few large-scale ways in which we may actively remove greenhouse gases from the atmosphere.

Given the likely demise of this substantial national export industry over the next few decades, we would be wise to think about what other innovative opportunities we can draw from the sector while it still has scale. Our coal miners are in the energy industry, but we would be foolish and simplistic if we think the only replacement industries emerging from coal is renewable energy.

We have a coal export industry simply because we have an area of natural advantage in coal i.e. high quality coal resources with rail and port access. We are yet to identify an equivalent area of natural advantage in renewables that could power a similarly scaled export industry. Yes we have sun and wind in abundance, but there is no real mechanism yet to export that to an international market.

But all is not lost. Mines are large consumers of energy and technology resources and have management responsibilities for significant tracts of the Australian landscape.

With the right guidance and incentives, the industry may yet lay the foundations for a sustainable legacy for our national economy and local communities in exportable products such as an innovative approach to professional services, transport technology and high intensity food production.


Gary will be on hand for an Author Q&A between 10 and 11am AEST on Wednesday, December 16, 2015. Post your questions in the comments section below.

The Conversation

Gary Ellem, Conjoint Academic in Sustainability, University of Newcastle

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

The Paris Agreement won’t stop coal, but future climate talks might


Luke Kemp, Australian National University

The global climate deal reached at the Paris climate talks has left a big question unanswered: what do to about coal? It isn’t even mentioned in the agreement text.

There is growing recognition that continued expansion of fossil fuels is incompatible with stopping dangerous climate change. If the international community wishes to limit global warming to a maximum of 2℃, only 886 billion tonnes of carbon dioxide (CO₂) can be emitted between 2000 and 2050. Locked in the ground is 2,795 billion tonnes, 65% of which is coal.

Given this simple maths, only one-fifth of these fossil fuels can be dug up. Most fossil fuel reserves cannot be used. Creating new coal mines or searching for new sources is not compatible with avoiding dangerous climate change. It is simply wasted investment.

This has provided the basis for the “no new coalmines” campaign. It is an idea that has gained traction around the world. So is it legally possible to undertake such a drastic international action?

Growing support

A global moratorium on new coal mines is rapidly gaining international support. The idea has even passed the lips of world leaders. On the summit’s opening day, Kiribati’s president Anote Tong told the assembled heads of state:

I have issued a call for a global moratorium on new investments on coal mines as endorsed by my fellow Pacific Leaders and I invite you all to join this call.

The climate talks have traditionally focused on tackling fossil fuel demand by attempting to limit countries’ overall greenhouse gas emissions. Beyond the negotiations, restricting the supply of fossil fuels is becoming the centre of attention.

The divestment movement has experienced considerable success in persuading concerned citizens and institutions to pull their money out of fossil fuel companies. The Obama administration recently rejected the Keystone XL pipeline, partly on the rationale that it undercuts US climate leadership.

Political support is increasing rapidly and could soon reach a tipping point that leads to international legal action either through, or outside of, the UN climate negotiations.

Through the climate convention

While Paris will not deliver a global moratorium on new coal mines, or even a dialogue about it, it could still happen in the near future. There are climate conferences every year and each one adopts a set of new decisions.
Countries could decide in the future to develop further rules for the pledging process, including putting forward what national actions are being taken to limit fossil fuel extraction.

Another option would be simply to amend the text of the United Nations Framework Convention on Climate Change (UNFCCC), or the Paris agreement at a later date. For the UNFCCC this could be done by a three-quarter majority vote (although the changes would only apply to countries who vote for and ratify the amendment).

The UNFCCC’s subsidiary body for science and technology could also be empowered to make recommendations on fossil fuel extraction, given a 2℃ carbon budget. This body has looked at carbon budget issues previously and has reviewed the temperature target.

Looking at the implications of fossil fuel extraction would be a logical step forward, and well within the body’s abilities. This could provide the basis for recommendations to the wider negotiations on what reaching 2℃ means for coal. Spoiler: new coal reserves are not compatible with the 2℃ threshold.

A political problem

The UN is not the only game in town. Some of the most powerful international institutions, such as the World Bank and World Trade Organisation (WTO), operate outside of the UN.

It’s feasible that a small group of countries could forge ahead to create their own semi-global agreement outside of the UN. This is not without precedence. The WTO was originally the General Agreement on Trades and Tariffs (GATT) with only 34 members.

Such an agreement could involve a group of countries pledging to ban the creation or expansion of coal infrastructure within their own sovereign borders, and to encouraging others to do so. They could even create regulations to forbid the purchase of coal from specific sources (new coal mines), although this would probably face technical issues and be challenged as arbitrary discrimination under the WTO, as has previously happened for Venezuelan gas exports.

At the very least, an agreement could establish a ruling for governments to divest from projects or companies involved in the expansion and creation of coal mines, or of fossil fuels in general.

Such a move may seem fruitless given that it would be taken by a coalition of the willing and would probably not involve major coal exporters. But as pointed out above, agreements rarely stay frozen in time. If designed correctly they can grow in membership and influence.

A multi-country agreement on no new coal mines could help to create a powerful new international norm, and help to signal a market push away from new coal mines and coal in general.

Stopping the creation and expansion of coal mines is not a legal problem. Numerous legal avenues to implement a moratorium on new coal exist. It is a purely political problem.

The world appears to be awakening to the simple fact that limiting warming to 2℃ means we cannot use existing coal reserves, let alone seek out new ones. The question is who will act first: the UN climate talks, or a critical mass of willing countries?

The Conversation

Luke Kemp, Lecturer and PhD Candidate in International Relations and Environmental Policy, 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?

The Conversation

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

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