Green cement a step closer to being a game-changer for construction emissions



If the cement industry were a country, it would be the third-largest emitter of CO₂ in the world.
Joe Mabel/Wikimedia, CC BY-SA

Yixia (Sarah) Zhang, Western Sydney University; Khin Soe, Western Sydney University, and Yingying Guo, UNSW

Concrete is the most widely used man-made material, commonly used in buildings, roads, bridges and industrial plants. But producing the Portland cement needed to make concrete accounts for 5-8% of all global greenhouse emissions. There is a more environmentally friendly cement known as MOC (magnesium oxychloride cement), but its poor water resistance has limited its use – until now. We have developed a water-resistant MOC, a “green” cement that could go a long way to cutting the construction industry’s emissions and making it more sustainable.

Producing a tonne of conventional cement in Australia emits about 0.82 tonnes of carbon dioxide (CO₂). Because most of the CO₂ is released as a result of the chemical reaction that produces cement, emissions aren’t easily reduced. In contrast, MOC is a different form of cement that is carbon-neutral.

Global CO₂ emissions from rising cement production over the past century (with 95% confidence interval).
Source: Global CO2 emissions from cement production, Andrew R. (2018), CC BY



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What exactly is MOC?

MOC is produced by mixing two main ingredients, magnesium oxide (MgO) powder and a concentrated solution of magnesium chloride (MgCl₂). These are byproducts from magnesium mining.

Magnesium oxide (MgO) powder (left) and a solution of magnesium chloride (MgCl₂) are mixed to produce magnesium oxychloride cement (MOC).
Author provided

Many countries, including China and Australia, have plenty of magnesite resources, as well as seawater, from which both MgO and MgCl₂ could be obtained.

Furthermore, MgO can absorb CO₂ from the atmosphere. This makes MOC a truly green, carbon-neutral cement.




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MOC also has many superior material properties compared to conventional cement.

Compressive strength (capacity to resist compression) is the most important material property for cementitious construction materials such as cement. MOC has a much higher compressive strength than conventional cement and this impressive strength can be achieved very fast. The fast setting of MOC and early strength gain are very advantageous for construction.

Although MOC has plenty of merits, it has until now had poor water resistance. Prolonged contact with water or moisture severely degrades its strength. This critical weakness has restricted its use to indoor applications such as floor tiles, decoration panels, sound and thermal insulation boards.

How was water-resistance developed?

A team of researchers, led by Yixia (Sarah) Zhang, has been working to develop a water-resistant MOC since 2017 (when she was at UNSW Canberra).

Adding industrial byproducts fly ash (above) and silica fume (below) improves the water resistance of MOC.
Author provided

To improve water resistance, the team added industrial byproducts such as fly ash and silica fume to the MOC, as well as chemical additives.

Fly ash is a byproduct from the coal industry – there’s plenty of it in Australia. Adding fly ash significantly improved the water resistance of MOC. Flexural strength (capacity to resist bending) was fully retained after soaking in water for 28 days.

To further retain the compressive strength under water attack, the team added silica fume. Silica fume is a byproduct from producing silicon metal or ferrosilicon alloys. When fly ash and silica fume were combined with MOC paste (15% of each additive), full compressive strength was retained in water for 28 days.

Both the fly ash and silica fume have a similar effect of filling the pore structure in MOC, making the cement denser. The reactions with the MOC matrix form a gel-like phase, which contributes to water repellence. The extremely fine particles, large surface area and high reactive silica (SiO₂) content of silica fume make it an effective binding substance known as a pozzolan. This helps give the concrete high strength and durability.

Scanning electron microscope images of MOC showing the needle-like phases of the binding mechanism.
Author provided



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Although the MOC developed so far had excellent resistance to water at room temperature, it weakened fast when soaked in warm water. The team worked to overcome this by using inorganic and organic chemical additives. Adding phosphoric acid and soluble phosphates greatly improved warm water resistance.

Examples of building products made using MOC.
Author provided

Over three years, the team has made a breakthrough in developing MOC as a green cement. The strength of concrete is rated using megapascals (MPa). The MOC achieved a compressive strength of 110 MPa and flexural strength of 17 MPa. These values are a few times greater than those of conventional cement.

The MOC can fully retain these strengths after being soaked in water for 28 days at room temperatures. Even in hot water (60˚C), the MOC can retain up to 90% of its compressive and flexural strength after 28 days. The values remain as high as 100 MPa and 15 MPa respectively – still much greater than for conventional cement.

Will MOC replace conventional cement?

So could MOC replace conventional cement some day? It seems very promising. More research is needed to demonstrate the practicability of uses of this green and high-performance cement in, for example, concrete.

When concrete is the main structural component, steel reinforcement has to be used. Corrosion of steel in MOC is a critical issue and a big hurdle to jump. The research team has already started to work on this issue.

If this problem can be solved, MOC can be a game-changer for the construction industry.




Read more:
The problem with reinforced concrete


The Conversation


Yixia (Sarah) Zhang, Associate Professor of Engineering, Western Sydney University; Khin Soe, Research Associate, School of Computing, Engineering and Mathematics, Western Sydney University, and Yingying Guo, PhD Candidate, School of Engineering and Information Technology, UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Our shameful legacy: just 15 years’ worth of emissions will raise sea level in 2300



Indonesian residents wade through flood water near the Ciliwung river in Jakarta in February 2018. Our emissions in the near future will lock in sea level rise over centuries.

Bill Hare, Potsdam Institute for Climate Impact Research

Greenhouse gas emissions released over the first 15 years of the Paris Agreement would alone lock in 20cm of sea-level rise in centuries to come, according to new research published today.

The paper shows that what the world pumps into the atmosphere today has grave long-term consequences. It underscores the need for governments to dramatically scale up their emission reduction ambition – including Australia, where climate action efforts have been paltry.

The report is the first to quantify the sea-level rise contribution of human-caused greenhouse gas emissions that countries would release if they met their current Paris pledges.

The 20cm sea-level rise is equal to that observed over the entire 20th century. It would comprise one-fifth of the 1m sea level rise projected for 2300.

A satellite image showing meltwater ponding in northwest Greenland near the ice sheet’s edge.
EPA/NASA EARTH OBSERVATORY

The picture is bleak

The study was led by researchers at Climate Analytics and the Potsdam Institute for Climate Impact Research, and was published today by the Proceedings of the National Academy of Sciences. It estimated the sea level rise to be locked in by 2300 due to greenhouse gas emissions between 2016 and 2030 – the first pledge period on the Paris treaty.

During those 15 years, emissions would cause sea levels to rise by 20cm by 2300. Even if the world cut all emissions to zero in 2030, sea levels would still rise in 2300. These estimates do not take into account the irreversible melting of parts of the Antarctic ice sheet.




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The researchers found that just over half of the sea level rise can be attributed to the top five polluters: China, the US, the European Union, India and Russia.

The emissions of these jurisdictions under will cause seas to rise by 12cm by 2300, the study shows.

The important takeaway message is that what the world does now will take years to play out – it is a stark warning of the long-term consequences of our actions.

Severe storms at Collaroy on Sydney’s northern beaches caused major damage to beachfront homes.
UNSW WATER RESEARCH

It’s worse than we thought

Last week a separate paper in Nature Communications showed sea-level rise could affect many more people than previously thought. The authors produced a new digital elevation model that showed many of the world’s coastlines are far lower than estimated with standard methods.

In low-lying parts of coastal Australia, for example, the previous data has
overestimated elevation by an average of 2.5m.

Their projections for the millions of people to be affected by sea-level rise are frightening. Within three decades, rising sea levels could push chronic floods higher than land currently home to 300 million people. By 2100, areas home to 200 million people could be permanently below the high tide line.

But what of Australia, girt by sea?

Australia is a coastal nation: the vast majority of our population lives within 50km of the sea, and will be heavily impacted by sea-level rise. Already, we’re seeing severe coastal erosion and inundation during king tides – and that’s without factoring in the impact of storm surges.

Clearly the world needs strong climate action to reduce greenhouse gas emissions as fast as possible. The Intergovernmental Panel on Climate Change has said emissions must be lowered to 45% below 2010 levels by 2030 and to zero by mid-century.

We also know that unless the world achieves this, we will not just lose parts of our coasts but also iconic ecosystems such as the Great Barrier Reef.



Australia’s emissions comprise a relatively small proportion of the global total – 1.4% or around 5% if we count coal and liquified natural gas exports. However, we have a much bigger diplomatic and political influence on the international stage.




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Australia should use its position to push for urgent action internationally. But the federal government’s appalling record on emissions reduction – despite its efforts to claim otherwise – puts us in a very weak position on the global stage. We cannot point fingers at other nations while our emissions rise and we sell as much coal as possible to the rest of the world, while also burning as much as we can.



All the while, Australia is becoming the poster child for extreme sea-level events, more frequent and severe bushfires and other devastating climate impacts.

Governments, including Australia’s, must put forward much stronger 2030 emission reduction pledges by 2020. There should seek to decarbonise at a pace in line with the Paris Agreement’s 1.5°C temperature goal.

Otherwise, our emissions today will cause seas to rise far into the future. This process cannot be reversed – it will be our legacy to future generations.


Climate Analytics researcher Alexander Nauels was lead author of the study.The Conversation

Bill Hare, Director, Climate Analytics, Adjunct Professor, Murdoch University (Perth), Visiting scientist, Potsdam Institute for Climate Impact Research

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Australia’s hidden opportunity to cut carbon emissions, and make money in the process



A seagrass meadow. For the first time, researchers have counted the greenhouse gases stored by and emitted from such ecosystems.
NOAA/Heather Dine

Oscar Serrano, Edith Cowan University; Carlos Duarte, King Abdullah University of Science and Technology; Catherine Lovelock, The University of Queensland; Paul Lavery, Edith Cowan University, and Trisha B Atwood, Utah State University

It’s no secret that cutting down trees is a main driver of climate change. But a forgotten group of plants is critically important to fixing our climate — and they are being destroyed at an alarming rate.

Mangroves, tidal marshes and seagrasses along Australia’s coasts store huge amounts of greenhouse gases, known as blue carbon.

Our research, published in Nature Communications, shows that in Australia these ecosystems absorb 20 million tonnes of carbon dioxide each year. That’s about the same as 4 million cars.




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Worryingly, the research shows that between 2 million and 3 million tonnes of carbon dioxide is released each year by the same ecosystems, due to damage from human activity, severe weather and climate change.

This research represents the world’s most comprehensive audit of any nation’s blue carbon. Around 10% of such ecosystems are located in Australia — so preserving and restoring them could go a long way to meeting our Paris climate goals.

A pile of washed-up seaweed and beach erosion at Collaroy Beach on Sydney’s northern beaches. Storms can damage blue carbon ecosystems.
Megan Young/AAP

Super-charged carbon dioxide capture

Blue carbon ecosystems are vital in curbing greenhouse gas emissions. They account for 50% of carbon dioxide sequestered by oceans — despite covering just 0.2% of the world’s total ocean area — and absorb carbon dioxide up to 40 times faster than forests on land.

They do this by trapping particles from water and storing them in the soil. This means tidal marsh, mangrove and seagrass ecosystems bury organic carbon at an exceptionally high rate.

Globally, blue carbon ecosystems are being lost twice as fast as tropical rainforests despite covering a fraction of the area.

Since European settlement, about 25,000km² of tidal marsh and mangroves and 32,000km² of seagrass have been destroyed – up to half the original extent. Coastal development in Australia is causing further losses each year.

When these ecosystems are damaged — through storms, heatwaves, dredging or other human development — the carbon stored in biomass and soils can make its way back into the environment as carbon dioxide, contributing to climate change.

In Western Australia in the summer of 2010-11, about 1,000km² of seagrass meadows at Shark Bay were lost due to a marine heatwave. Similarly, two cyclones and several other impacts devastated a 400km stretch of mangroves in the Gulf of Carpentaria in recent years.

The beach and Cape Kimberley hinterland at the mouth of the Daintree River in Queensland.
Brian Cassey/AAP

Such losses likely increase carbon dioxide emissions from land-use change in Australia by 12–21% per year.

Aside from the emissions reduction benefits, conserving and restoring blue carbon ecosystems would also increase the resilience of coasts to rising sea level and storm surge associated with climate change, and preserve habitats and nurseries for marine life.

How we measured blue carbon – and why

The project was part of a collaboration with CSIRO and included 44 researchers from 33 research institutions around the world.

To accurately quantify Australia’s blue carbon stocks, we divided Australia into five different climate zones. Variations in temperature, rainfall, tides, sediments and nutrients mean plant productivity and biomass varies across regions. So ecosystems in a tropical climate such as North Queensland store carbon dioxide at a different rate to those in temperate climates such as southeastern Australia.




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We estimated carbon dioxide stored in the vegetation above ground and soils below for each climate area. We measured the size and distribution of vegetation and took soil core samples to create the most accurate measurements possible.

Blue carbon must be assessed on a national scale before policies to preserve them can be developed. These policies might involve replanting seagrass meadows, reintroducing tidal flow to restore mangroves or preventing potential losses caused by coastal development.

Seagrass at Queensland’s Gladstone Harbour.
James Cook University

There’s a dollar to be made

Based on a carbon price of A$14 per tonne – the most recent price under the federal government’s Emissions Reduction Fund – blue carbon projects could be worth tens of millions of dollars per year in carbon credits. Our comprehensive measurements provide greater certainty of expected returns for financiers looking at investing in such projects.

Restoring just 10% of blue carbon ecosystems lost in Australia since European settlement could generate more than US$11 million per year in carbon credits. Conserving such ecosystems under threat could be worth between US$22 million and US$31 million per year.




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Blue carbon projects cannot currently be counted towards Australia’s Paris targets, but federal environment authorities are developing a methodology for their inclusion. The reintroduction of tidal flow to restore mangrove and tidal marsh ecosystems has been identified as the most promising potential activity.

Other activities being explored include planning for sea level rise to allow mangrove and tidal marsh to migrate inland, and avoiding the clearing of seagrass and mangroves.

There are still questions to be answered about exactly how blue carbon can be used to mitigate climate change. But our research shows the massive potential in Australia, and allows other countries to use the work for their own blue carbon assessments.The Conversation

Oscar Serrano, ARC DECRA Fellow, Edith Cowan University; Carlos Duarte, Adjunct professor, King Abdullah University of Science and Technology; Catherine Lovelock, Professor of Biology, The University of Queensland; Paul Lavery, Professor of Marine Ecology, Edith Cowan University, and Trisha B Atwood, Assistant Professor of aquatic ecology, Utah State University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

What if we measured the thing that matters most: “carbon productivity”


Carbon productivity is the measure that matters, but we are hung up on the productivity of our workers.
pixabay/pexels

David Peetz, Griffith University

Ask any economist a question, and you will usually get the answer: “productivity”.

The winner of the 2008 Nobel Prize in Economics, Paul Krugman, set the standard in 1994:

Productivity isn’t everything, but, in the long run, it is almost everything. A country’s ability to improve its standard of living over time depends almost entirely on its ability to raise its output per worker.

The new head of Australia’s treasury, Steven Kennedy, said much the same thing this week:

The most important long-term contribution to wage growth is labour productivity.

For my money, they could say the same about “carbon productivity”, a idea that is going to matter to us more.

Labour productivity is notoriously hard to measure; measuring changes in it is harder still.

It’s relatively easy to measure in the jobs we are doing less of these days, such as making washing machines; harder to measure in the jobs we are doing more of, such as caring for people.

And it’s less important than you might think. People aren’t a particularly finite resource. Allowable carbon emissions are.

Carbon is the input that matters

Economist Paul Krugman. ‘In the long run productivity is almost everything.’
CHRISTOPHER BARTH/EPA

The Intergovernmental Panel on Climate Change says net carbon emissions will have to be reduced to zero.

That means we’ve a carbon budget, a limited amount of greenhouse gas we can emit from here on. It would make sense to use it wisely.

What I am proposing is a target for “carbon productivity”, the amount of production we achieve from each remaining unit of emissions – as a means of helping us cut overall carbon emissions.

It’s easy to calculate: gross domestic product divided by net emissions. We already measure GDP, and we already measure emissions in tonnes, albeit unevenly.

We are going to need huge increases in carbon productivity, much more so as a result of cutting emissions than increasing production.

Things that are good for labour productivity might well be bad for carbon productivity. For example, replacing a sweeper with an air blower is good on the first count, bad on the second.

Measuring carbon productivity…

If introduced at a national level, a target, or at least a widely published measure, could start to focus government minds on what’s important and what’s not, and assist in allocating resources. Solar farms would become more likely to gain support than coal-fired power plants.

Regulatory resources might be redirected in surprising ways. While a small number of large emitters constitutes an easy target for policymakers, if those large emitters are efficient, the government might find it has to move its focus to the larger number of small inefficient emitters.

It could also help us think about how we resolve the conflict between the perceived need for economic growth and the need to substantially cut emissions. Both would be important, the measures that achieved both would be the most important.

Accounting debates about whether to carry carry forward international credits would be rendered meaningless.




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Giving national attention to measuring carbon productivity would put more pressure on more firms to measure all of their emissions. Many already measure their “scope 1” direct emissions. A smaller number measure “scope 2” emissions (from things such as electricity used by the firm).

A much smaller number measure “scope 3” emissions (from sources they do not own, such as air travel, waste and water). They’re the hardest to measure.

…might just produce results

For some, sustainable economic growth is a contradiction in terms.

They argue that economic growth is incompatible with ecological survival.

But the population appears to want both, and the political and social consequences of failing to achieve both could be devastating for democratic society and the planet. It has already been established that rising unemployment reduces support for action on climate change.




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Targeting or measuring carbon productivity by itself won’t achieve those goals.

For that, we would need some form of carbon pricing and a government committed to the uptake of low-emission technologies.

But if we are to have a shot at achieving both, we’ll need to know where we are going.The Conversation

David Peetz, Professor of Employment Relations, Centre for Work, Organisation and Wellbeing, Griffith University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Some good news for a change: Australia’s greenhouse gas emissions are set to fall



Renewable energy being installed at a community in the Northern Territory. Researchers have predicted Australia’s emissions are set to fall, but warn the renewables deployment rate must continue.
Lucy Hughes-Jones/AAP

Andrew Blakers, Australian National University and Matthew Stocks, Australian National University

For the past few years, Australia’s greenhouse gas emissions have headed in the wrong direction. The upward trajectory has come amid overwhelming evidence that the world must bring carbon dioxide emissions down. But the trend is set to change.

In a policy brief released today, we predict that Australia’s greenhouse gas emissions will peak during 2019-20 at the equivalent of about 540 million tonnes of carbon dioxide.

After a brief plateau, we expect they will decline by 3-4% over 2020-22, and perhaps much more in the following years – if backed by government policy.

The peak will occur because Australia’s world-leading deployment of solar and wind energy is displacing fossil fuel combustion. Emissions from the electricity sector are about to fall much faster than increases in emissions from all other sectors combined.

This is a message of hope for rapid reduction of emissions at low cost. But we cannot rest on our laurels. If renewable energy deployment stops or slows, emissions may rise again.

Figure 1: Historical and projected total Australian emissions in megatonnes of CO2 (equivalent) per year. Black line: Government emissions projections which assume solar and wind deplpoyment almost stops. Green line: Deployment continues at the current rate.
ANU

Australia: a renewables superstar

Deployment of solar and wind energy is the cheapest and quickest way to make deep emissions cuts because of its low and falling cost. Higher deployment rates would yield deeper emissions cuts, but this requires supportive government policy.

Wind and solar constitute about two-thirds of global net new electricity capacity. Gas, hydro and coal comprise most of the balance. Solar and wind comprise virtually all new generation capacity in Australia because they are cheaper than alternatives.




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Australia is a global renewable energy superstar because it is installing new solar and wind capacity four to fives times faster per capita than China, the European Union, Japan or the United States. This allows Australia to stabilise and then reduce its greenhouse emissions and sends a globally important message.

Figure 2 shows the rapid increase in the proportion of solar and wind energy from 2018 in the National Electricity Market, which covers the eastern states and comprises about 85% of national electricity generation. The proportion of renewable energy generation has reached 25%, including hydro.

Figure 2: Monthly solar and wind fraction of electricity generation in the NEM over 2014-19 showing sharp increase in 2018.
ANU

We are confident Australia’s emissions will fall in 2020, 2021 and probably 2022 because 16-17 gigawatts of wind and solar is locked in for deployment in 2018-20. This reduces emissions in the electricity sector by about 10 million tonnes a year.

The federal government projects that emissions outside the electricity system will increase by about 3 million tonnes per year on average over the 2020s. The difference leaves an overall decline of 7 million tonnes of emissions per year.

100% clean electricity is within our grasp

Beyond our projections for the next few years, continued falls in emissions are not assured. The emissions trajectory for 2022 and beyond depends largely on the level of renewables deployed.

Federal government projections assume solar and wind deployment almost stops in the 2020s. This would mean annual emissions increase from current levels to 563 million tonnes in 2030.

Wind turbines adjacent to the Tesla batteries at Jamestown, north of Adelaide, in 2017.
DAVID MARIUZ/AAP

But it doesn’t need to be this way. If the current renewables deployment rate continued, Australia would reach 50% renewable electricity in 2024, and potentially 80% renewables in 2030. This transformation would be technically straightforward and affordable. It requires governments, mostly the federal government, to encourage more transmission power lines to deliver renewable electricity to where it’s needed. Other off-the-shelf methods to support renewables include energy storage such as pumped hydro and batteries, and managing electricity demand.

The benefits of a consistent renewables rollout would be large. Australia’s electricity emissions in 2030 would be 100 million tonnes lower than government projections and the nation would meet its Paris target of a 26-28% emissions reduction between 2005 and 2030. This could be achieved without the controversial proposal to carry over carbon credits earned in the Kyoto Protocol period.

It should be noted that changes in land clearing rates or coal and gas mining or economic activity would also affect future national emissions.

Electricity infrastructure at the Snowy Hydro scheme. Such hydro projects are key to firming up intermittent renewable energy.
Lukas Coch/AAP

The emissions road ahead

Continued rapid deployment of solar and wind requires that governments enable construction of adequate electricity transmission and storage.

State governments should also continue efforts to establish renewable energy zones, with or without cooperation from the federal government. These zones would be located where there is good wind, sun and pumped hydro energy storage, bringing sustainable investment and jobs to regional areas.




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In the longer term, solar and wind can cut national emissions by two-thirds. Beyond the electricity sector, this involves electrifying motor vehicles, residential heating and cooling and industrial heating. National emissions could be cut by another 10% by stopping exports of fossil fuels, which creates fugitive emissions.

It is clear that solar and wind are the most practical route, globally and in Australia, to cheap, rapid and deep emissions cuts – and government policy will be key.The Conversation

Andrew Blakers, Professor of Engineering, Australian National University and Matthew Stocks, Research Fellow, ANU College of Engineering and Computer Science, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Climate explained: how volcanoes influence climate and how their emissions compare to what we produce



Rapid and voluminous volcanic eruptions around 252 million years ago can be linked with a mass extinction event.
from http://www.shutterstock.com, CC BY-ND

Michael Petterson, Auckland University of Technology


CC BY-ND

Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz

Everyone is going on about reducing our carbon footprint, zero emissions, planting sustainable crops for biodiesel etc. Is it true what the internet posts say that a volcano eruption for a few weeks will make all our efforts null and void?

The pretext to this question is understandable. The forces of nature are so powerful and operate at such a magnitude that human efforts to influence our planet may seem pointless.

If one volcanic eruption could alter our climate to such a degree that our world rapidly becomes an “icehouse” or a “hothouse”, then perhaps our efforts to mitigate anthropogenic climate change are a waste of time?

To answer this question we need to examine how our atmosphere formed and what geological evidence there is for volcanically induced climate change. We also need to look at recent data comparing volcanic and human greenhouse gas emissions.

There is evidence for catastrophic climate change from very large, protracted volcanic eruptions in the geological record. But in more recent times we have learned that volcanic emissions can lead to shorter-term cooling and longer-term warming. And the killer-punch evidence is that human-induced greenhouse gas emissions far exceed those of volcanic activity, particularly since 1950.

Forging Earth’s atmosphere

Let’s go back to first principles and look at where our atmosphere came from. Earth is 4.56 billion years old. The common consensus is that Earth’s atmosphere results from three main processes:

1. remnants of primordial solar nebula gases from the time of earliest planet formation

2. outgassing of the Earth’s interior from volcanic and related events

3. the production of oxygen from photosynthesis.

There have also been contributions over time from comets and asteroid collisions. Of these processes, internal planetary degassing is the most important atmosphere-generating process, particularly during the first of four aeons of Earth’s history, the hot Hadean.

Volcanic eruptions have contributed to this process ever since and provided the bulk of our atmosphere and, therefore, the climate within our atmosphere.

Next is the question of volcanic eruptions and their influence on climate. Earth’s climate has changed over geological time. There have been periods of an ice-free “hothouse Earth”. Some argue that sea levels were 200 to 400 metres higher than today and a significant proportion of Earth’s continents were submerged beneath sea level.

At other times, during a “snowball Earth”, our planet was covered in ice even at the equator.




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What contribution have volcanic eruptions made to this variation in climate? As an example of a major influence, some scientists link mass extinctions to major volcanic eruption events.

The most famous such association is that of the eruption of volcanoes that produced the Siberian Traps. This is a large region of thick volcanic rock sequences, some 2.5 to 4 million square kilometres, in an area in Russia’s eastern provinces. Rapid and voluminous volcanic eruptions around 252 million years ago released sufficient quantities of sulphate aerosols and carbon dioxide to trigger short-duration volcanic winters, and long-duration climate warming, over a period of 10s of thousands of years.

The Siberian Trap eruptions were a causal factor in Earth’s largest mass extinction event (at the end of the Permian period), when 96% of Earth’s marine species and 70% of terrestrial life ceased to exist.

Natural climate change over past 100 million years

Geological evidence indicates that natural processes can indeed radically change Earth’s climate. Most recently (in geological terms), over the past 100 million years ocean bottom waters have cooled, sea levels fallen and ice has advanced. Within this period there have also been spells of a hotter Earth, most likely caused by (natural) rapid releases in greenhouse gases.

Homo sapiens has evolved during the past few million years largely during an ice age when up to two-kilometre-thick ice sheets covered large areas of the northern continents and sea levels were over 100 metres lower than today. This period ended 10,000 years ago when our modern interglacial warmer period began.

Astronomical cycles that lead to climate variations are well understood – for example, the Milankovitch cycles, which explain variations in Earth’s orbit around the sun, and the periodic nodding/swaying of our Earth’s axis. All of the geological and tectonic causes for this general longer-term Earth cooling are less well understood. Hypotheses include contributions from volcanoes and processes linked to the rise of the Himalayas and Tibet (from 55 million years ago).




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Specific volcanic eruptions and climate impacts

Researchers have studied specific volcanic eruptions and climate change. Mount Pinatubo (Philippines) produced one of the larger eruptions of recent times in 1991, releasing 20 million tonnes of sulphur dioxide and ash particles into the stratosphere.

These larger eruptions reduce solar radiation reaching the Earth’s surface, lower temperatures in the lower troposphere, and change atmospheric circulation patterns. In the case of Pinatubo, global tropospheric temperatures fell by up to 4°C, but northern hemisphere winters warmed.

Volcanoes erupt a mix of gases, including greenhouse gases, aerosols and gases that can react with other atmospheric constituents. Atmospheric reactions with volcanic gases can rapidly produce substances such as sulphuric acid (and related sulphates) that act as aerosols, cooling the atmosphere.

Longer-term additions of carbon dioxide have warming impacts. Larger-scale volcanic eruptions, whose ash clouds reach stratospheric levels, have the biggest climatic impacts: the larger and more prolonged the eruption period, the larger the impacts.

These types of eruptions are thought to have been a partial cause for the Little Ice Age period, a global cooling event of about 0.5°C that lasted from the 15th to the late 19th century. Super volcanoes such as Yellowstone (USA), Toba (Indonesia) and Taupo (New Zealand) can, theoretically, produce very large-volume eruptions that have significant climate impacts, but there is uncertainty over how long these eruptions influence climate.

Perhaps the strongest evidence for answering whether our (human) emissions or volcanoes have a stronger influence on climate lies in the scale of greenhouse gas production. Since 2015, global anthropogenic carbon dioxide emissions have been around 35 to 37 billion tonnes per year. Annual volcanic CO₂ emissions are around 200 million tonnes.

In 2018, anthropogenic CO₂ emissions were 185 times higher than volcanic emissions. This is an astounding statistic and one of the factors persuading some geologists and natural scientists to propose a new geological epoch called the Anthropocene in recognition that humans are exceeding the impacts of many natural global processes, particularly since the 1950s.

There is evidence that volcanoes have strongly influenced climate on geological time scales, but, since 1950 in particular, it is Homo sapiens who has had by far the largest impact on climate. Let us not give up our CO₂ emission-reduction aspirations. Volcanoes may not save the day.The Conversation

Michael Petterson, Professor of Geology, Auckland University of Technology

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Double counting of emissions cuts may undermine Paris climate deal


Ice floe adrift in Vincennes Bay in the Australian Antarctic Territory. There are fears efforts to combat global warming will be undermined by double counting of carbon credits.
AAP/Torsten Blackwood

Frank Jotzo, Crawford School of Public Policy, Australian National University; Lambert Schneider, Oeko-Institut, and Maosheng DUAN, Tsinghua University

In the four years since the Paris climate agreement was adopted, countries have debated the fine print of how emissions reduction should be tracked and reported. One critical detail is proving particularly hard to work out – and a weak result would threaten the environmental integrity of the entire deal.

The sticking point is rules for carbon markets: specifically, how to prevent double counting of emissions reductions by both the country selling and buying carbon credits.

These rules are proving a major barrier to reaching consensus. In December, the negotiations move to Chile for this year’s major climate talks, known as COP25. The double counting issue needs to be resolved. It will not be an easy job, and the outcome matters to many countries, including Australia.




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The Morrison government says Australia will meet the Paris emissions targets by 2030 without international trading – partly by counting old carbon credits towards its Paris efforts. But in future Australia may adopt a stronger target in line with global climate goals. This may entail government and businesses buying carbon credits from overseas.

In an article just published in the journal Science, we and our co-authors* explain why double counting could undermine the Paris goals, and how a robust outcome could be achieved.

The Port Kembla industrial works in Wollongong. Industrial activity is a major contributor to overall global emissions.
AAP/Deal Lewins

What’s the problem here?

International carbon trading allows two or more countries to achieve their emissions targets more cheaply than if going it alone. Countries where cutting emissions is relatively cheap do more than is required by their targets. They then sell the additional emissions reductions, in the form of credits, to countries that find it harder to achieve their targets.

Carbon credits could be produced through activity such as replacing fossil fuels with zero-emissions energy, greater energy efficiency and electrification in transport and buildings, new technologies in industry and better practices in agriculture and forestry.

Rules for carbon trading are defined under Article 6 of the Paris agreement. Trading under the deal could be big: almost half the parties to the agreement have signalled they want to use carbon markets. Airlines might also become major buyers of emissions credits, under rules requiring them to offset increases in carbon emissions from international flights above 2020 levels.

The cost savings from using carbon markets could make it easier for countries to adopt more ambitious targets – ultimately resulting in greater emissions reductions.




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But if trading rules are not watertight then the use of carbon markets could lead to greater emissions, undermining the agreement.

One fundamental risk is double counting: a country selling a carbon credit might claim the underlying emissions reduction for itself, while at the same time the country buying the credit also claims the same emissions reduction.

Obviously any international transfer of emission reductions should not lead to higher total emissions than if participating countries had met their targets individually. This could be ensured through a form of double-entry bookkeeping, wherein the country selling carbon credits adjusts its emissions upwards, and the country acquiring the carbon credits adjusts, by the same amount, downwards.

But the devil lies in the detail – and in the self interest of the parties involved.

Planes lined up at Sydney Airport. The aviation industry will likely buy carbon credits to offset its emissions growth from 2020.
AAP

The bones of contention

Countries are wrangling over what double counting is, how it should be avoided and whether it should sometimes be allowed.

Some countries hoping to sell emissions credits, notably Brazil, propose rules under which emissions reductions sold to another country could effectively also be claimed by the selling country. Such rules existed under the Kyoto Protocol, which came before the Paris agreement. However under Kyoto developing countries did not have emission targets. All major countries have emissions targets under Paris, making the method unsuitable now.




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Another potential pitfall lies in the potential purchase by international airlines of large amounts of credits to offset increases in their emissions. Aviation emissions are not counted in national emissions inventories. So it would be logical to adjust the selling country’s inventory for any emissions reduction sold to airlines.

But some countries, notably Saudi Arabia, argue that this should not be done because the airline industry is governed by a separate international treaty. This approach would allow emissions reductions to be included in both agreements and counted twice.

In a separate point of debate some countries – including Australia, Canada, Japan, and the United States – oppose the idea of a single international body overseeing carbon trading under the Paris agreement, arguing for more national sovereignty and flexibility between nations buying and selling.

Making things even more complex, the Paris agreement allows each country to determine how to frame their emissions target. Some countries frame them as absolute emissions, others as a reduction relative to business-as-usual, or as a ratio of emissions to gross domestic product. Some countries’ targets are simply unclear.

A deforested area in the Amazon forest in Brazil. Carbon credits can be earned by nations that retain forest rather than cutting it down.
Marcelo Sayao/EPA

Letting each country determine its own ambitions and approach was key in making the Paris agreement a reality. But it makes accounting for carbon markets more complex.

There are also questions over whether a portion of carbon trading revenue should be allocated to help pay for climate change resilience in developing countries, and whether old credits from a trading scheme under the Kyoto Protocol, the Clean Development Mechanism, should be tradable in the new scheme.

The way forward in Chile

The solutions to all these issues will be nuanced, but will require that governments agree on some fundamentals.

The first is that a single set of common international accounting rules should apply, irrespective of which carbon market mechanism is used by countries or groups of countries.

The second is to ensure robust emissions accounting, regardless of how mitigation targets are expressed.

The third is that over time, all countries should move toward economy-wide emissions targets, as the Paris Agreement foresees.

The need to reach a political deal in Chile must not result in loopholes for international carbon markets. The rules must ensure environmental integrity and avoid double counting. If this is achieved, emissions reductions can be made more cheaply and global ambition can be more readily raised. If not, then the accord could be seriously undermined.

The article in the journal Science “Double counting and the Paris Agreement rulebook” is authored by Lambert Schneider, Maosheng Duan, Robert Stavins, Kelley Kizzier, Derik Broekhoff, Frank Jotzo, Harald Winkler, Michael Lazarus, Andrew Howard, Christina Hood. See here for the full manuscript.The Conversation

Frank Jotzo, Director, Centre for Climate and Energy Policy, Crawford School of Public Policy, Australian National University; Lambert Schneider, Research coordinator for international climate policy, Oeko-Institut, and Maosheng DUAN, professor, Tsinghua University

This article is republished from The Conversation under a Creative Commons license. Read the original article.