Humanity and the Planet
Monthly Archives for October 2018
The science is clear: we have to start creating our low-carbon future today
Alan Finkel, Office of the Chief Scientist
This week’s release of the special report from the Intergovernmental Panel on Climate Change (IPCC) has put scientific evidence on the front page of the world’s newspapers.
As Australia’s Chief Scientist, I hope it will be recognised as a tremendous validation of the work that scientists do.
The people of the world, speaking through their governments, requested this report to quantify the impacts of warming by 1.5℃ and what steps might be taken to limit it. They asked for the clearest possible picture of the consequences and feasible solutions.
Read more:
The UN’s 1.5°C special climate report at a glance
It is not my intention in this article to offer a detailed commentary on the IPCC’s findings. I commend the many scientists with expertise in climate systems who have helped Australians to understand the messages of this report.
My purpose is to urge all decision-makers – in government, industry and the community – to listen to the science.
Focus on the goal
It would be possible for the public to take from this week’s headlines an overwhelming sense of despair.
The message I take is that we do not have time for fatalism.
We have to look squarely at the goal of a zero-emissions planet, then work out how to get there while maximising our economic growth. It requires an orderly transition, and that transition will have to be managed over several decades.
That is why my review of the National Electricity Market called for a whole-of-economy emissions reduction strategy for 2050, to be in place by the end of 2020.
Read more:
The Finkel Review at a glance
We have to be upfront with the community about the magnitude of the task. In a word, it is huge.
Many of the technologies in the IPCC’s most optimistic scenarios are at an early stage, or conceptual. Two that stand out in that category are:
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carbon dioxide removal (CDR): large-scale technologies to remove carbon dioxide from the atmosphere.
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carbon capture and sequestration (CCS): technology to capture and store carbon dioxide from electricity generation.
It will take a decade or more for these technologies to be developed to the point at which they have proven impact, then more decades to be widely deployed.
The IPCC’s pathways for rapid emissions reduction also include a substantial role for behavioural change. Behavioural change is with us always, but it is incremental.
Driving change of this magnitude, across all societies, in fundamental matters like the homes we build and the foods we eat, will only succeed if we give it time – and avoid the inevitable backlash from pushing too fast.
The IPCC has made it clear that the level of emissions reduction we can achieve in the next decade will be crucial. So we cannot afford to wait.
Many options
No option should be ruled off the table without rigorous consideration.
In that context, the Finkel Review pointed to a crucial role for natural gas, particularly in the next vital decade, as we scale up renewable energy.
The IPCC has made the same point, not just for Australia but for the world.
The question should not be “renewables or coal”. The focus should be on atmospheric greenhouse emissions. This is the outcome that matters.
Denying ourselves options makes it harder, not easier, to get to the goal.
There also has to be serious consideration of other options modelled by the IPCC, including biofuels, catchment hydroelectricity, and nuclear power.
My own focus in recent months has been on the potential for clean hydrogen, the newest entrant to the world’s energy markets.
Read more:
How hydrogen power can help us cut emissions, boost exports, and even drive further between refills
In future, I expect hydrogen to be used as an alternative to fossil fuels to power long-distance travel for cars, trucks, trains and ships; for heating buildings; for electricity storage; and, in some countries, for electricity generation.
We have in Australia the abundant resources required to produce clean hydrogen for the global market at a competitive price, on either of the two viable pathways: splitting water using solar and wind electricity, or deriving hydrogen from natural gas and coal in combination with carbon capture and sequestration.
Building an export hydrogen industry will be a major undertaking. But it will also bring jobs and infrastructure development, largely in regional communities, for decades.
So the scale of the task is all the more reason to press on today – at the same time as we press on with mining lithium for batteries, clearing the path for electric vehicles, planning more carbon-efficient cities, and so much more.
There are no easy answers. I hope, through this and other reports, there are newly determined people ready to contribute to the global good.
Alan Finkel, Australia’s Chief Scientist, Office of the Chief Scientist
This article is republished from The Conversation under a Creative Commons license. Read the original article.
We need more carbon in our soil to help Australian farmers through the drought
Evie Shaffer/Unsplash
Nanthi Bolan, University of Newcastle
Australia has never been a stranger to droughts, but climate change is now super-charging them.
Besides taking a toll on human health, droughts also bake the earth. This means the ground holds less water, creating a vicious cycle of dryness.
Our research has investigated ways to improve the health and structure of soil so it can hold more water, even during droughts. It’s vital to help farmers safeguard their soil as we adapt to an increasingly drought-prone climate.
Read more:
Australia moves to El Niño alert and the drought is likely to continue
Soil moisture is key
The immediate effect of drought is complete loss of soil water. Low moisture reduces soil health and productivity, and increases the loss of fertile top soil through wind and water erosion.
To describe how we can improve soil health, we first need to explain some technical aspects of soil moisture.
Author provided
Soil moisture is dictated by three factors: the ability of the soil to absorb water; its capacity to store that water; and the speed at which the water is lost through evaporation and runoff, or used by growing plants.
These three factors are primarily determined by the proportions of sand, silt and clay; together these create the “soil structure”. The right mixture means there are plenty of “pores” – small open spaces in the soil.
Read more:
How to fight desertification and drought at home and away
Soils dominated by very small “micropores” (30-75 micrometres), such as clay soil, tend to store more water than those dominated by macropores (more than 75 micrometers), such as sandy soil.
If the balance is skewed, soil can actually repel water, increasing runoff. This is a major concern in Australia, especially in some areas of Western Australia and South Australia.
Improving soil structure
Good soil structure essentially means it can hold more water for longer (other factors include compaction and surface crust).
Farmers can improve soil structure by using minimum tillage, crop rotation and return of crop residues after harvest.
Another important part of the puzzle is the amount of organic matter in the soil –it breaks down into carbon and nutrients, which is essential for absorbing and storing water.
There are three basic ways to increase the amount of organic matter a given area:
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grow more plants in that spot, and leave the crop and root residue after harvest
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slow down decomposition by tilling less and generally not disturbing the soil more than absolutely necessary
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apply external organic matter through compost, mulch, biochar and biosolids (treated sewage sludge).
Typically, biosolids are used to give nutrients to the soil, but we researched its impact on carbon storage as well. When we visited a young farmer in Orange, NSW, he showed us two sites: one with biosolids, and one without. The site with biosolids grew a bumper crop of maize the farmer could use as fodder for his cattle; the field without it was stunted.
The farmer told us the extra carbon had captured more moisture, which meant strong seedling growth and a useful crop.
Read more:
On dangerous ground: land degradation is turning soils into deserts
This illustrates the value of biowastes including compost, manure, crop residues and biosolids in capturing and retaining moisture for crop growth, reducing the impact of drought on soil health and productivity.
Improving soil health cannot happen overnight, and it’s difficult to achieve while in midst of a drought. But how farmers manage their soil in the good times can help prepare them for managing the impacts of the next drought when it invariably comes.
The author would like to thank Dr Michael Crawford, CEO of Soil CRC, for his substantial contribution to this article.
Nanthi Bolan, Professor of Enviornmental Science, University of Newcastle
This article is republished from The Conversation under a Creative Commons license. Read the original article.
New UN report outlines ‘urgent, transformational’ change needed to hold global warming to 1.5°C
Mark Howden, Australian National University and Rebecca Colvin, Australian National University
A landmark report from the Intergovernmental Panel on Climate Change, commissioned at the breakthrough 2015 summit that brokered the Paris climate agreement, outlines what’s at stake in the world’s bid to limit global temperature rise to 1.5℃.
The report, released today, sets out the key practical differences between the Paris agreement’s two contrasting goals: to limit the increase of human-induced global warming to well below 2℃, and to “pursue efforts” to limit warming to 1.5℃.
Read more:
The UN’s 1.5°C special climate report at a glance
Two and a half years in the making, the report provides vital information about whether the Paris Agreement’s more ambitious goal is indeed achievable, what the future may look like under it, and the risks and rewards of hitting the target.
Here are five key questions to which the report provides answers.
Can we limit warming to 1.5℃?
There is no clear yes or no answer to this question.
Put simply, it is not impossible that global warming could be limited to 1.5℃. But achieving this will be profoundly challenging.
If we are to limit warming to 1.5℃, we must reduce carbon dioxide emissions by 45% by 2030, reaching near-zero by around 2050.
Whether we are successful primarily depends on the rate at which government and non-state bodies take action to reduce emissions. Yet despite the urgency, current national pledges under the Paris Agreement are not enough to remain within a 3℃ temperature limit, let alone 1.5℃.
Global warming is not just a problem for the future. The impacts are already being felt around the world, with declines in crop yields, biodiversity, coral reefs, and Arctic sea ice, and increases in heatwaves and heavy rainfall. Sea levels have risen by 40.5mm in the past decade and are predicted to continue rising for decades, even if all greenhouse emissions were reduced to zero immediately. Climate adaptation is already needed and will be increasingly so at 1.5℃ and 2℃ of warming.
Rapid action is essential and the next ten years will be crucial. In 2017, global warming breached 1℃. If the planet continues to warm at the current rate of 0.2℃ per decade, we will reach 1.5℃ of warming around 2040. At current emissions rates, within the next 10 to 14 years there is a 2/3 chance we will have used up our entire carbon budget for keeping to 1.5.
How can we limit warming to 1.5℃?
The report says “transformational” change will be needed to limit warming to 1.5℃. Business as usual will not get us there.
Global emissions of carbon dioxide, methane and other greenhouse gases need to reach net zero globally by around 2050. Most economists say putting a price on emissions is the most efficient way to do this.
By 2050, 70-85% of electricity globally will need to be supplied by renewables. Investment in low-carbon and energy-efficient technologies will need to double, whereas investment in fossil-fuel extraction will need to decrease by around a quarter.
CIFOR/Flickr, CC BY-NC
Carbon dioxide removal technology will also be needed to remove greenhouse gases from the atmosphere. But the IPCC’s report warns that relying too heavily on this technology would be a major risk as it has not been used on such a large scale before. Carbon dioxide removal is an extra step that may be needed to keep warming to 1.5℃, not an excuse to keep emitting greenhouse gases.
Production, consumption and lifestyle choices also play a role. Reducing energy demand and food waste, improving the efficiency of food production, and choosing foods and goods with lower emissions and land use requirements will contribute significantly.
Taking such action as soon as possible will be hugely beneficial. The earlier we start, the more time we have to reach net zero emissions. Acting early will mean a smoother transition and less net cost overall. Delay will lead to more haste, higher costs, and a harder landing.
Reducing emissions quickly will also ensure warming is capped as soon as possible, reducing the number and severity of impacts.
Yet severe impacts will still be experienced even if warming is successfully capped at 1.5℃.
What is the cost of 1.5℃ of warming?
Although the Paris Agreement aims to hold global warming as close to 1.5℃ as possible, that doesn’t mean it is a “safe” level. Communities and ecosystems around the world have already suffered significant impacts from the 1℃ of warming so far, and the effects at 1.5℃ will be harsher still.
Poverty and disadvantages will increase as temperatures rise to 1.5℃. Small island states, deltas and low-lying coasts are particularly vulnerable, with increased risk of flooding, and threats to freshwater supplies, infrastructure, and livelihoods.
Warming to 1.5℃ also poses a risk to global economic growth, with the tropics and southern subtropics potentially being hit hardest. Extreme weather events such as floods, heatwaves, and droughts will become more frequent, severe, and widespread, with attendant costs in terms of health care, infrastructure, and disaster response.
The oceans will also suffer in a 1.5℃ warmer world. Ocean warming and acidification are expected to impact fisheries and aquaculture, as well as many marine species and ecosystems.
OIST/Flickr, CC BY
Up to 90% of warm water coral reefs are predicted to disappear when global warming reaches 1.5℃. That would be a dire situation, but far less serious than at 2℃, when the destruction of coral reefs would be almost total (greater than 99% destruction).
How do 1.5℃ and 2℃ compare?
Impacts on both human and natural systems would be very different at 1.5℃ rather than 2℃ of warming. For example, limiting warming to 1.5℃ would roughly halve the number of people globally who are expected to suffer from water scarcity.
Seas would rise by an extra 10cm this century at 2℃ compared with 1.5℃. This means limiting global warming to 1.5℃ would save up to 10.4 million people from the impacts of rising seas.
At 1.5℃ rather than 2℃:
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up to 427 million fewer people will suffer food and water insecurity, climate risks, and adverse health impacts
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extreme weather events, heat-related death and disease, desertification, and wildlife extinctions will all be reduced
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it will be significantly easier to achieve many of the United Nations’ Sustainable Development Goals, including those linked to hunger, poverty, water and sanitation, health, and cities and ecosystems.
How does the 1.5℃ target fit with the Sustainable Development Goals?
The Sustainable Development Goals aim for a world in which people can be healthy, financially stable, well fed, have clean air and water, and live in a secure and pleasant environment. Much of this is consistent with the goal of capping global warming at 1.5℃, which is why the IPCC notes there are synergies if the SDG initiatives and climate action should be explicitly linked.
But some climate strategies may make it harder to achieve particular SDGs. Countries that are highly dependent on fossil fuels for employment and revenue may suffer economically in the transition towards low-carbon energy.
Carefully managing this transition by simultaneously focusing on reducing poverty and promoting equity in decision-making may help avoid the worst effects of such trade-offs. What works in one place may not work in another, so strategies should always be locally appropriate.
Where next?
Limiting global warming to 1.5℃ will require a social transformation, as the world takes rapid action to reduce greenhouse gases. The effects of climate change will continue to shape the world we live in, but there is no doubt we will be far better off under 1.5℃ than 2℃ of global warming.
Read more:
Why is climate change’s 2 degrees Celsius of warming limit so important?
The choices we make today are shaping the future for coming generations. As the new report makes clear, if we are serious about the 1.5℃ target, we need to act now.
The authors gratefully acknowledge the substantial contribution to authorship of this article by of Lamis Kazak, an Australian National University Bachelor of Interdisciplinary Studies (Sustainability) student, as part of a Science Communication Internship with the Climate Change Institute.
Mark Howden, Director, Climate Change Institute, Australian National University and Rebecca Colvin, Knowledge Exchange Specialist, Climate Change Institute, Australian National University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Australia and Deforestation
Australia has two decades to avoid the most damaging impacts of climate change
Iain Stewart, ClimateWorks Australia
The long-awaited special report on the science underpinning the Paris Agreement goal of limiting global warming to 1.5℃ has been released today by the Intergovernmental Panel on Climate Change.
It tells us that hitting this goal will be challenging, but not impossible. And it highlights the benefits of hitting the target, by pointing out that global warming will be vastly more damaging if allowed to reach 2℃.
Read more:
The UN’s 1.5°C special climate report at a glance
The report says that for a 66% chance at limiting global warming to 1.5℃, an additional 550 billion tonnes of carbon dioxide (or its equivalent) can be emitted globally from the beginning of 2018. Increasing the risk to a 50% chance at limiting global warming to 1.5℃, that figure becomes 750Gt CO₂e.
Based on previous calculations, Australia’s fair share of the global carbon budget is roughly equivalent to 1%. That would put Australia’s remaining carbon budget at 5.5Gt and 7.5Gt for a 66% and 50% chance, respectively.
The simplified trajectory below shows that Australia would therefore need to reach net zero greenhouse emissions by 2038 for a 66% chance of limiting global warming to 1.5℃, and by 2045 for a 50% chance.
ClimateWorks Australia, Author provided
In practical terms, this gives Australia two decades to deliver on our part, for a good chance of avoiding the most devastating impacts of a warming climate. Globally, we must reach net zero greenhouse emissions by 2047 for a 66% chance of limiting global warming to 1.5℃, and by 2058 for a 50% chance. Australia will have to hit net zero before it is achieved globally because we currently have among the highest per person emissions, so our decarbonisation trajectory needs to be steeper.
But Australia’s emissions are rising
From 2006 to 2013, Australian emissions decreased, but they have since begun to rise again. As shown in ClimateWorks Australia’s recently released report, Tracking Progress, we are not yet on track meet our current Paris commitment of cutting emissions by 26-28% relative to 2005 levels by 2030. Nor are we on track to reach net zero.
Yet our research also showed we have the potential to get back on track. There have been recent periods when sectors of our economy have cut carbon at or near the pace required to achieve net zero emissions by 2050.
Read more:
Australia is not on track to reach 2030 Paris target (but the potential is there)
Reaching net zero from here will require rapid, economy-wide action, including:
- increasing the share of renewable electricity
- improving energy efficiency
- electrifying transport and industry where possible
- switching to lower-emission fuels such as gas
- land use changes (reforestation, reduced land clearance, and best practice farming).
There are already many examples of these kinds of approaches. For example, since 2010, solar photovoltaic prices have fallen by around 70% and battery prices by around 80%, while uptake rates have surpassed expectations. This has been the result of research, investment, government incentives, shifting consumer preferences, and economies of scale.
Consumers are beginning to embrace trends such as electric vehicles and 3D printing, and we can expect more technological disruptions throughout the economy such as building optimisation, smart grids, and solar-hydrogen, which all have the potential to reduce emissions significantly.
The goal is still in reach (just)
The new IPCC report is adamant that the goal of limiting global warming to 1.5℃ is still achievable – despite previous fears that it is already out of reach. Yes, it is tight, but the challenge is in going faster, not the lack of solutions.
Crucially, the report also points out that 2℃ of global warming would be vastly more damaging than 1.5℃, and that 2℃ cannot be treated as a “safe” limit.
At 2℃, the report predicts it is “very likely that there will be at least one sea-ice-free Arctic summer per decade”. In contrast, holding warming to 1.5℃ rather than 2℃ would protect an extra 10.4 million people from rising sea levels.
Some of these people are our neighbours in Pacific Island nations, many of which are implementing some of the most ambitious climate policies in the world. For low-lying countries and island states, the reality is “1.5 to stay alive”.
Australia’s climate at stake
Closer to home, the impacts of climate change on Australia will continue to manifest themselves in extreme weather events such as droughts, floods and bushfires. Increasing impacts are expected to extend to water, food and even border security, creating the potential for millions of climate refugees in our region before the end of the century.
As a wealthy, emissions-intensive country with abundant natural resources, in a region highly vulnerable to climate impacts, Australia should take its Paris climate targets very seriously. Australia has the means to become a regional leader in climate action, positioning ourselves as a “clean energy superpower” and helping our neighbours work towards becoming carbon-neutral.
Read more:
Lack of climate policy threatens to trip up Australian diplomacy this summit season
There are many examples within Australia of commitments already made to reach net zero emissions. States and territories representing 80% of Australia’s emissions – along with the federal opposition – have committed to reaching net zero emissions by 2050. Tasmania has already reached net zero. The ACT has legislated to do so by 2045.
Other organisations have also pledged to go carbon-neutral or use 100% renewable energy, including multinational companies, major cities such as Melbourne, Sydney and Adelaide, and universities.
These initiatives prove that setting targets for emissions reduction actually ignites action. The IPCC’s new report sets us perhaps the most important target of all: the world must hit net zero emissions by mid-century if we are to stand a good chance of avoiding the worst impacts of global warming.
Iain Stewart, Analyst, ClimateWorks Australia
This article is republished from The Conversation under a Creative Commons license. Read the original article.
The UN’s 1.5°C special climate report at a glance
Emil Jeyaratnam, The Conversation; Madeleine De Gabriele, The Conversation, and Michael Hopkin, The Conversation
The Intergovernmental Panel on Climate Change released a special report today on the impacts of global warming of 1.5℃ above pre-industrial levels.
The report outlines the considerable challenges of meeting the Paris Agreement’s more ambitious goal of limiting warming to 1.5℃, the global effort needed to achieve the target, and the consequences of not.
The highlights of the report are presented below:
CC BY-ND
Correction: A previous version of this article stated that the Australian Labor Party had a goal of reaching 50% renewable energy by 2050. But the ALP hope to achieve the 50% target via an emissions intensity scheme by 2030.
Emil Jeyaratnam, Data + Interactives Editor, The Conversation; Madeleine De Gabriele, Deputy Editor: Energy + Environment, The Conversation, and Michael Hopkin, Section Editor: Energy + Environment, The Conversation
This article is republished from The Conversation under a Creative Commons license. Read the original article.
The black wattle is a boon for Australians (and a pest everywhere else)
Wikipedia/The Conversation
Gregory Moore, University of Melbourne
Sign up to the Beating Around the Bush newsletter here, and suggest a plant we should cover at batb@theconversation.edu.au.
The genus Acacia is Australia’s largest, containing nearly 1,000 different species. It includes our national floral emblem, the golden wattle, and is the source of the green and gold colours of many of our sporting teams. The variety of acacias is mind-boggling.
There are many well-known small, short-lived species that thrive both in their natural habitats and in suburban gardens, where they are known for attracting insects and birds. There are species that survive in the arid inland as inconspicuous, stunted shrubs that are more than 200 years old, and there are also tall forest trees such as the blackwood, Acacia melanoxylon that can live for centuries.
Read more:
The art of healing: five medicinal plants used by Aboriginal Australians
The black wattle, Acacia mearnsii, falls somewhere between these extremes. It ranges from 6 metres up to (occasionally) 15 metres in height. It is generally called “short-lived”, but often makes it past 20 years old, and may persist for 30 years or more under the right conditions.
The Conversation, CC BY
It has attractive bi-pinnate (feathery) leaves, dark green foliage, and smooth, dark bark – hence its common name. It has the typical pale yellow to golden wattle flower. Its pea-like fruits are typically 10mm wide and up to 150mm long, which as they dry out can rattle on the tree. These fruits contain many tough, black seeds that can readily germinate if damaged, which breaks the hard seed coat. This explains the high weed potential, but makes them easy to propagate.
Different indigenous groups used wattles for various purposes. Seeds were often consumed as food. The bark of many species, including black wattle, was used for coarse rope and string, and the tannins and gums in the bark of black wattle were used as adhesives. Indeed, they are still used in the manufacture of some modern veneered and laminated timbers. An infusion of the bark in water has also been used for medicinal purposes.
Vinayaraj/Wikipedia, CC BY
Unusually, black wattle is probably better known and used outside Australia. Its fame and infamy stem from the fact that it has been grown for more than a century as far afield as South Africa, Portugal and Germany.
It was grown in plantations here and overseas, as its bark and wood contain high levels of chemicals called tannins, used in tanning leather. Indeed, many of the famous horse-riding paths, such as the Melbourne tan track around the botanic gardens, were once surfaced with black wattle waste from tanneries. The infamy arises because in many places, including parts of Australia, it is regarded as a highly invasive weed.
Read more:
Do you know a Bunji from a Boorie? Meet our dictionary’s new Indigenous words
The tree was also grown locally and in places like India as a source of firewood and timber for light construction. It is easily killed by fire, but can also sucker prolifically, which can give rise to dense thickets that virtually eliminate other species. The bark and crevices are home to many insects, fungi and bacteria. Some arborists who have worked with the species dislike its brittle wood, as broken twigs and branches can easily cut workers with a risk of subsequent infection. So be wary when working with it!
KENPEI/Wikipedia, CC BY
Given its occurrence over a large part of southeastern Australia, black wattle occurs naturally in a diverse range of habitats, from open eucalypt forests to drier woodlands and grasslands in New South Wales, Victoria, South Australia and Tasmania. It grows well in low rainfall, and in the heavy clays of the great basalt plain that extends from the outskirts of Melbourne to beyond the South Australian border.
Read more:
National parks are vital for protecting Australia’s endangered plants
This is a great fillip to the garden, as it requires little irrigation and has the added advantage of telling you when it needs water. When the plant is dry its leaves, which are usually open and in full display, noticeably close up. This is the time to give it a good drink.
In tougher environments where it is windy, frosty or very sunny, black wattle can be planted as a quick-growing tree among which other slower-growing and more sensitive species can be planted. The black wattle provides protection for these other tree species, and as it ages and starts to collapse (often at around 15 years) the other trees emerge and take over.
As for all acacias, black wattle is a nitrogen-fixing plant. This means its roots have bacteria that allow it to take nitrogen from the atmosphere and incorporate it into the plant’s structure, which also benefits the surrounding soil. This can be a real advantage to those establishing a garden in poorer soils or heavy clays.
Read more:
The Lord Howe screw pine is a self-watering island giant
The black wattle can also provide excellent natural mulch both in large-scale revegetation projects and domestic gardens. The mulch forms from the leaves and bark as they are shed, but also from the twigs and branches as the plant dies.
In the right parts of Australia, where it grows naturally, the black wattle is a valuable plant for revegetation work and an asset in the garden.
Gregory Moore, Doctor of Botany, University of Melbourne
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Explosive lies: how volcanoes can lie about their age, and what it means for us
from http://www.shutterstock.com, CC BY-ND
Richard N Holdaway; Ben Kennedy, and Brendan Duffy, University of Melbourne
Just like a teenager wanting to be older, volcanoes can lie about their age, or at least about their activities. For kids, it might be little white lies, but volcanoes can tell big lies with big consequences.
Our research, published today in Nature Communications, uncovers one such volcanic lie.
Accurate dating of prehistoric eruptions is important as it allows scientists to correlate them with other records, such as large earthquakes, Antarctic ice cores, historical events like Mediterranean civilisation milestones, and climatic events like the Little Ice Age. This gives us a better understanding of the links between volcanism and the natural and cultural environment.
Taupo’s last violent eruption
Lake Taupo, in the North Island of New Zealand, is a globally significant caldera supervolcano. The caldera formed after the collapse of a magma chamber roof following a massive eruption more than 20,000 years ago.
Now it seems that the Taupo eruption that occurred in the early part of the first millennium has been lying about its age. But like many lies, it was eventually found out, and it reveals exciting processes we hadn’t understood before.
The eruption of Taupo in the first millennium has been dated many times with radiocarbon, yielding a surprisingly large spread of ages between 36CE and 538CE.
Read more:
Curious Kids: Why do volcanoes erupt?
Radiocarbon dating of eruptions
Radiocarbon dating of organic material is based on the concentrations of radioactive carbon-14 in a sample remaining after the organisms’ death. Over the past two decades, the method has been refined greatly by combining it with dendrochronology, the study of the environmental effects on the width of tree rings through time.
Radiocarbon dating of tree ring records has allowed scientists to construct a reliable record of the concentration of carbon-14 in the atmosphere through time.
In principle, this composite record allows eruptions to be dated by matching the wiggly trace of carbon-14 in a tree killed by an eruption to the wiggly trace of atmospheric carbon-14 from the reference curve (“wiggle-match” dating).
Scientists presently use wiggle-match dating as the method of choice for eruption dating, but the technique is not valid if carbon dioxide gas from the volcano is affecting a tree’s version of the wiggle.
Read more:
Bali’s Agung – using ‘volcano forensics’ to map the past, and predict the future
The effect of volcanic carbon on eruption ages
Our study re-analysed the large series of radiocarbon dates for the Taupo eruption and found that the oldest dates were closest to the volcano vent. The dates were progressively younger the farther away they were.
Provided by authors, CC BY-ND
This unusual geographic pattern has been documented very close (i.e. less than a kilometre) to volcanic vents before, but never on the scale of tens of kilometres. Two wiggle match ages, taken from the same forest, located about 30km from the caldera lake, were among the oldest dates from the series of dates.
This enlarged influence of the volcano can be explained by the influence of groundwater beneath the lake and its surroundings. The Taupo wiggle-match tree grew in a dense forest in a swampy valley where volcanic carbon dioxide was seeping out of the ground and was incorporated in the trees.
Provided by authors, CC BY-ND
The ratio of carbon-13 to carbon-12 (the two stable isotopes of carbon) in the modern water of Lake Taupo and the Waikato River tells us that volcanic carbon dioxide is getting into the groundwater from an underlying magma body.
Can large eruptions be forecast over decades?
Our study shows that a large and increasing volume of carbon dioxide gas containing these stable isotopes was emitted from deep below the prehistoric Taupo volcano. It was then redistributed by the region’s huge groundwater system, ultimately becoming incorporated into the wood of the dated trees.
The increase was sufficiently large over several decades to dramatically alter the ratios of different carbon isotopes in the tree wood. The forest was subsequently killed by the last part of the Taupo eruption series. But the dilution of atmospheric carbon-14 by volcanic carbon made the radiocarbon dates for tree material from the Taupo eruption appear somewhere between 40 and 300 years too old.
The precursory change in carbon ratios gives us a way to gain insight into the forecasting of future eruptions, a central goal in volcanology. We found that the radiocarbon dates and isotope data that underpin the presently accepted “wiggle match” age reached a plateau (that is, stopped evolving normally). This meant that for several decades before the eruption, the outer growth rings of trees had ‘weird’ carbon ratios, forecasting the impending eruption.
We re-analysed data from other major eruptions, including at Rabaul in Papua New Guinea and Baitoushan on the North Korean border with China and found similar patterns. The anomalous chemistry mimics but exceeds the Suess effect, which reversed the carbon isotopic evolution of post-industrial wood. This implies that measurements of carbon isotopes in 200-300 annual rings can track changes in the carbon source used by trees growing near a volcano, providing a potential method of forecasting future large eruptions.
We anticipate that this will provide a significant focus for future research at supervolcanoes around the globe.
Richard N Holdaway, Adjunct Professor; Ben Kennedy, , and Brendan Duffy, Lecturer in Applied Geoscience, University of Melbourne
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Moving Break
I will be taking a break from Blogging for the next 2 to 3 weeks. It has become necessary for me to move home and this will be taking place over this period – so it’s packing, cleaning, transporting, etc, for the next few weeks. I may be able to get back to Blogging before 3 weeks, we’ll see how the move all goes. There is a lot to do though.
Kevin's Walk on the Wild Side 
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