New research: nitrous oxide emissions 300 times more powerful than CO₂ are jeopardising Earth’s future


Pep Canadell, CSIRO; Eric Davidson, University of Maryland, Baltimore; Glen Peters, Center for International Climate and Environment Research – Oslo; Hanqin Tian, Auburn University; Michael Prather, University of California, Irvine; Paul Krummel, CSIRO; Rob Jackson, Stanford University; Rona Thompson, Norwegian Institute for Air Research, and Wilfried Winiwarter, International Institute for Applied Systems Analysis (IIASA)

Nitrous oxide from agriculture and other sources is accumulating in the atmosphere so quickly it puts Earth on track for a dangerous 3℃ warming this century, our new research has found.

Each year, more than 100 million tonnes of nitrogen are spread on crops in the form of synthetic fertiliser. The same amount again is put onto pastures and crops in manure from livestock.

This colossal amount of nitrogen makes crops and pastures grow more abundantly. But it also releases nitrous oxide (N₂O), a greenhouse gas.

Agriculture is the main cause of the increasing concentrations, and is likely to remain so this century. N₂O emissions from agriculture and industry can be reduced, and we must take urgent action if we hope to stabilise Earth’s climate.

2000 years of atmospheric nitrous oxide concentrations. Observations taken from ice cores and atmosphere. Source: BoM/CSIRO/AAD.

Where does nitrous oxide come from?

We found that N₂O emissions from natural sources, such as soils and oceans, have not changed much in recent decades. But emissions from human sources have increased rapidly.

Atmospheric concentrations of N₂O reached 331 parts per billion in 2018, 22% above levels around the year 1750, before the industrial era began.

Agriculture caused almost 70% of global N₂O emissions in the decade to 2016. The emissions are created through microbial processes in soils. The use of nitrogen in synthetic fertilisers and manure is a key driver of this process.

Other human sources of N₂O include the chemical industry, waste water and the burning of fossil fuels.

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N₂O is destroyed in the upper atmosphere, primarily by solar radiation. But humans are emitting N₂O faster than it’s being destroyed, so it’s accumulating in the atmosphere.

N₂O both depletes the ozone layer and contributes to global warming.

As a greenhouse gas, N₂O has 300 times the warming potential of carbon dioxide (CO₂) and stays in the atmosphere for an average 116 years. It’s the third most important greenhouse gas after CO₂ (which lasts up to thousands of years in the atmosphere) and methane.

N₂O depletes the ozone layer when it interacts with ozone gas in the stratosphere. Other ozone-depleting substances, such as chemicals containing chlorine and bromine, have been banned under the United Nations Montreal Protocol. N₂O is not banned under the protocol, although the Paris Agreement seeks to reduce its concentrations.

A farmer emptying fertiliser into machinery
Reducing fertiliser use on farms is critical to reducing N₂O emissions.

What we found

The Intergovernmental Panel on Climate Change has developed scenarios for the future, outlining the different pathways the world could take on emission reduction by 2100. Our research found N₂O concentrations have begun to exceed the levels predicted across all scenarios.

The current concentrations are in line with a global average temperature increase of well above 3℃ this century.

We found that global human-caused N₂O emissions have grown by 30% over the past three decades. Emissions from agriculture mostly came from synthetic nitrogen fertiliser used in East Asia, Europe, South Asia and North America. Emissions from Africa and South America are dominated by emissions from livestock manure.

In terms of emissions growth, the highest contributions come from emerging economies – particularly Brazil, China, and India – where crop production and livestock numbers have increased rapidly in recent decades.

N₂O emissions from Australia have been stable over the past decade. Increase in emissions from agriculture and waste have been offset by a decline in emissions from industry and fossil fuels.

Regional changes in N₂O emissions from human activities, from 1980 to 2016, in million tons of nitrogen per year. Data from: Tian et al. 2020, Nature. Source: Global Carbon Project & International Nitrogen Initiative.

What to do?

N₂O must be part of efforts to reduce greenhouse gas emissions, and there is already work being done. Since the late 1990s, for example, efforts to reduce emissions from the chemicals industry have been successful, particularly in the production of nylon, in the United States, Europe and Japan.

Reducing emissions from agriculture is more difficult – food production must be maintained and there is no simple alternative to nitrogen fertilisers. But some options do exist.

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In Europe over the past two decades, N₂O emissions have fallen as agricultural productivity increased. This was largely achieved through government policies to reduce pollution in waterways and drinking water, which encouraged more efficient fertiliser use.

Other ways to reduce N₂O emissions from agriculture include:

  • better management of animal manure

  • applying fertiliser in a way that better matches the needs of growing plants

  • alternating crops to include those that produce their own nitrogen, such as legumes, to reduce the need for fertiliser

  • enhanced efficiency fertilisers that lower N₂O production.

Global nitrous oxide budget 2007-16. Adopted from Tian et al. 2020. Nature. Source: Global Carbon Project & International Nitrogen Initiative.

Getting to net-zero emissions

Stopping the overuse of nitrogen fertilisers is not just good for the climate. It can also reduce water pollution and increase farm profitability.

Even with the right agricultural policies and actions, synthetic and manure fertilisers will be needed. To bring the sector to net-zero greenhouse gas emissions, as needed to stabilise the climate, new technologies will be required.

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The Conversation

Pep Canadell, Chief research scientist, Climate Science Centre, CSIRO Oceans and Atmosphere; and Executive Director, Global Carbon Project, CSIRO; Eric Davidson, Director, Appalachian Laboratory and Professor, University of Maryland, Baltimore; Glen Peters, Research Director, Center for International Climate and Environment Research – Oslo; Hanqin Tian, Director, International Center for Climate and Global Change Research, Auburn University; Michael Prather, Distinguished Professor of Earth System Science, University of California, Irvine; Paul Krummel, Research Group Leader, CSIRO; Rob Jackson, Professor, Department of Earth System Science, and Chair of the Global Carbon Project, Stanford University; Rona Thompson, Senior scientist, Norwegian Institute for Air Research, and Wilfried Winiwarter, , International Institute for Applied Systems Analysis (IIASA)

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

Astronomers create 40% more carbon emissions than the average Australian. Here’s how they can be more environmentally friendly


Adam Stevens, University of Western Australia and Sabine Bellstedt, University of Western Australia

Astronomers know all too well how precious and unique the environment of our planet is. Yet the size of our carbon footprint might surprise you.

Our study, released today in Nature Astronomy, estimated the field produces 25,000 tonnes of carbon dioxide-equivalent emissions per year in Australia. With fewer than 700 active researchers nationwide (including PhD students), this translates to 37 tonnes per astronomer per year.

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As a point of reference, the average Australian adult was responsible for 26 tonnes of emissions in 2019, total. That means the job of being an astronomer is 40% more carbon-intensive than the average Australian’s job and home life combined.

While we often defer to governments for climate policy, our global carbon footprint can be dramatically reduced if every industry promotes strategies to reduce their own footprint. For individual industries to make progress, they must first recognise just how much they contribute to the climate emergency.

Where do all the emissions come from?

We found 60% of astronomy’s carbon footprint comes from supercomputing. Astronomers rely on supercomputers to not only process the many terabytes of data they collect from observatories everyday, but also test their theories of how the Universe formed with simulations.

Antennas and a satellite dish in the foreground, with others in the background, in the WA desert.
Antennas of CSIRO’s ASKAP telescope at the Murchison Radio-astronomy Observatory in Western Australia.
CSIRO Science Image

Frequent flying has historically been par for the course for astronomers too, be it for conference attendance or on-site observatory visits all around the world. Prior to COVID-19, six tonnes of annual emissions from flights were attributed to the average astronomer.

An estimated five tonnes of additional emissions per astronomer are produced in powering observatories every year. Astronomical facilities tend to be remote, to escape the bright lights and radio signals from populous areas.

Some, like the Parkes radio telescope and the Anglo-Australian Telescope near Coonabarabran, are connected to the electricity grid, which is predominately powered by fossil fuels.

Others, like the Murchison Radio-astronomy Observatory in Western Australia, need to be powered by generators on site. Solar panels currently provide around 15% of the energy needs at the Murchison Radio-astronomy Observatory, but diesel is still used for the bulk of the energy demands.

Finally, the powering of office spaces accounts for three tonnes of emissions per person per year. This contribution is relatively small, but still non-negligible.

They’re doing it better in Germany

Australia has an embarrassing record of per-capita emissions. At almost four times the global average, Australia ranks in the top three OECD countries for the highest per-capita emissions. The problem at large is Australia’s archaic reliance on fossil fuels.

A study at the Max Planck Institute for Astronomy in Germany found the emissions of the average astronomer there to be less than half that in Australia.

The difference lies in the amount of renewable energy available in Germany versus Australia. The carbon emissions produced for each kilowatt-hour of electricity consumed at the German institute is less than a third pulled from the grid in Australia, on average.

The challenge astronomers in Australia face in reducing their carbon footprint is the same challenge all Australian residents face. For the country to claim any semblance of environmental sustainability, a swift and decisive transition to renewable energy is needed.

Taking emissions reduction into our own hands

A lack of coordinated action at a national level means organisations, individuals, and professions need to take emissions reduction into their own hands.

For astronomers, private arrangements for supercomputing centres, observatories, and universities to purchase dedicated wind and/or solar energy must be a top priority. Astronomers do not control the organisations that make these decisions, but we are not powerless to effect influence.

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The good news is this is already happening. A recent deal made by Swinburne University to procure 100% renewable energy means the OzSTAR supercomputer is now a “green machine”.

CSIRO expects the increasing fraction of on-site renewables at the Murchison Radio-astronomy Observatory has the potential to save 2,000 tonnes of emissions per year from diesel combustion. And most major universities in Australia have released plans to become carbon-neutral this decade.

As COVID-19 halted travel worldwide, meetings have transitioned to virtual platforms. Virtual conferences have a relatively minute carbon footprint, are cheaper, and have the potential to be more inclusive for those who lack the means to travel. Despite its challenges, COVID-19 has taught us we can dramatically reduce our flying. We must commit this lesson to memory.

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And it’s encouraging to see the global community banding together. Last year, 11,000 scientists from 153 countries signed a scientific paper, warning of a global climate emergency.

As astronomers, we have now identified the significant size of our footprint, and where it comes from. Positive change is possible; the challenge simply needs to be tackled head-on.The Conversation

Adam Stevens, Research Fellow in Astrophysics, University of Western Australia and Sabine Bellstedt, Research Associate in Astronomy, University of Western Australia

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

Climate explained: methane is short-lived in the atmosphere but leaves long-term damage

Shutterstock/effective stock photos

Zebedee Nicholls, University of Melbourne and Tim Baxter, University of Melbourne


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

Methane is a shorter-lived greenhouse gas – why do we average it out over 100 years? By doing so, do we risk emitting so much in the upcoming decades that we reach climate tipping points?

The climate conversation is often dominated by talk of carbon dioxide, and rightly so. Carbon dioxide is the climate warming agent with the biggest overall impact on the heating of the planet.

But it is not the only greenhouse gas driving climate change.

Comparing apples and oranges

For the benefit of policy makers, the climate science community set up several ways to compare gases to aid with implementing, monitoring and verifying emissions reduction policies.

In almost all cases, these rely on a calculated common currency – a carbon dioxide-equivalent (CO₂-e). The most common way to determine this is by assessing the global warming potential (GWP) of the gas over time.

The simple intent of GWP calculations is to compare the climate heating effect of each greenhouse gas to that created by an equivalent amount (by mass) of carbon dioxide.

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In this way, emissions of one gas – like methane – can be compared with emissions of any other – like carbon dioxide, nitrous dioxide or any of the myriad other greenhouse gases.

These comparisons are imperfect but the point of GWP is to provide a defensible way to compare apples and oranges.

Limits of metrics

Unlike carbon dioxide, which is relatively stable and by definition has a GWP value of one, methane is a live-fast, die-young greenhouse gas.

Methane traps very large quantities of heat in the first decade after it is released in to the atmosphere, but quickly breaks down.

After a decade, most emitted methane has reacted with ozone to form carbon dioxide and water. This carbon dioxide continues to heat the climate for hundreds or even thousands of years.

Emitting methane will always be worse than emitting the same quantity of carbon dioxide, no matter the time scale.

How much worse depends on the time period used to average out its effects. The most commonly used averaging period is 100 years, but this is not the only choice, and it is not wrong to choose another.

As a starting point, the Intergovernmental Panel on Climate Change’s (IPCC) Fifth Assessment Report from 2013 says methane heats the climate by 28 times more than carbon dioxide when averaged over 100 years and 84 times more when averaged over 20 years.

Many sources of methane

On top of these base rates of warming, there are other important considerations.

Fully considered using the 100-year GWP and including natural feedbacks, the IPCC’s report says fossil sources of methane – most of the gas burned for electricity or heat for industry and houses – can be up to 36 times worse than carbon dioxide. Methane from other sources – such as livestock and waste – can be up to 34 times worse.

Some cattle at a farm in New Zealand
Livestock are a source of methane emission into the atmosphere.
Flickr/mikeccross, CC BY-NC-ND

While some uncertainty remains, a well-regarded recent assessment suggested an upwards revision of fossil and other methane sources, that would increase their GWP values to around 40 and 38 times worse than carbon dioxide respectively.

These works will be assessed in the IPCC’s upcoming Sixth Assessment Report, with the physical science contribution due in 2021.

While we should prefer the most up to date science at any given time, the choice to consider – or not – the full impact of methane and the choice to consider its impact over 20, 100 or 500 years is ultimately political, not scientific.

Undervaluing or misrepresenting the impact of methane presents a clear risk for policy makers. It is vital they pay attention to the advice of scientists and bodies such as the IPCC.

Undervaluing methane’s impact in this way is not a risk for climate modellers because they rely on more direct assessments of the impact of gases than GWP.

Tipping points

The idea of climate tipping points is that, at some point, we may change the climate so much that it crosses an irreversible threshold.

At such a tipping point, the world would continue to heat well beyond our capability to limit the harm.

There are many tipping points we should be aware of. But exactly where these are – and precisely what the implications of crossing one would be – is uncertain.

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Unfortunately, the only way we can be sure of where these tipping points are is to cross them. The only thing we know for sure about them is that the impact on lives, livelihoods and the places we love would be beyond catastrophic if we did.

But we cannot ignore disturbing impacts of climate change that are already here.

For example, damage to the landscape from the Black Summer bushfires may be irreversible and this represents its own form of climate tipping point.

The scientific understanding of climate change goes well beyond simple metrics like GWP. Shuffling between metrics – such as 20-year or 100-year GWP – cannot avoid the fact our very best chance of avoiding ever-worsening climate harm is to massively reduce our reliance on coal, oil and gas, along with reducing our emissions from all other sources of greenhouse gas.

If we do this, we offer ourselves the best chance of avoiding crossing thresholds we can never return from.The Conversation

Zebedee Nicholls, PhD Researcher at the Climate & Energy College, University of Melbourne and Tim Baxter, Fellow – Melbourne Law School; Senior Researcher – Climate Council; Associate – Australian-German Climate and Energy College, University of Melbourne

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

To reduce disasters, we must cut greenhouse emissions. So why isn’t the bushfire royal commission talking about this?


Robert Glasser, Australian National University

With next fire season already underway,
the bushfire royal commission yesterday released an interim report.

Its observations in the wake of our Black Summer suggest the commission’s final report, due on October 28, may recommend a major shake-up of how disaster management is governed at the federal level. This includes setting up a national body focused on recovery from and resilience to future disasters.

Most initial observations are uncontroversial and sensible, but there is a glaring omission. It involves the most urgent measure to reduce the risk of future disasters: reducing greenhouse gas emissions.

In my former role as the United Nations Secretary General’s Special Representative for Disaster Risk Reduction, I saw first-hand the impacts of natural disasters, and nations’ efforts to build their climate change resilience. The royal commission process is a unique opportunity to accelerate progress in these areas, which are so critical for Australia’s future.

What’s in the report?

In February, the royal commission was tasked with finding ways to improve disaster management in three main areas:

  1. how the federal government coordinates with other levels of government
  2. resilience to climate change and mitigating disaster risk
  3. the laws governing the federal government response to national emergencies.

The initial observations touch on each of these areas. This includes the need to collate, harmonise and share disaster data across jurisdictions; enhance research in climate and disaster resilience; reassess aerial firefighting capabilities; and plan more effectively around critical infrastructure.

It’s also worth noting the royal commission hasn’t yet formed a view on a key change Prime Minister Scott Morrison suggested was necessary in the wake of the bushfires: establishing the legal authority for the federal government to declare a national state of emergency. Currently, only state and territory governments have this power.

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And controversially, the commission suggests the long-standing role of the Australasian Fire and Emergency Service Authorities Council (AFAC) should be transferred to a federal government agency.

AFAC is a non-government organisation that facilitates the deployment of emergency personnel and equipment interstate and internationally. But the states and territories may not be willing to relinquish the engagement they have under the current arrangements.

A bushfire danger rating sign, pointing to 'extreme'
The royal commission also reported that many people said terms like ‘watch and act’ were confusing.

Most importantly, the royal commission is considering consolidating disaster recovery and resilience functions in a new national body.

These functions reside in at least three agencies. They include Emergency Management Australia, the National Bushfire Recovery Agency, and the National Drought and North Queensland Flood Response and Recovery Agency.

Consolidation makes good sense as the recovery phase from disasters can contribute to strengthening resilience.

It’s also sensible to separate the resilience function from the disaster response function, currently led by Emergency Management Australia. In my experience, resilience work rarely gets the whole-of-government attention it deserves when it’s embedded in agencies focused around responding to emergencies.

Three months of disasters

After the devastation Black Summer wrought, it’s clear resilience to future disasters must start with action on climate change. So it’s disappointing the royal commission has not yet commented on the need to lower greenhouse gas emissions as rapidly as possible.

Although COVID-19 has masked our awareness of the rapidly increasing climate threat, the evidence — even over just the past three months — is overwhelming.

In June, the record was set for the highest temperature ever recorded in the Arctic. The associated unprecedented heatwave in Siberia contributed to massive bushfires razing an astonishing 20 million hectares.

While Siberia burned, severe floods devastated South Asia, China and Japan. One-third of Bangladesh was underwater, affecting almost 15 million people.

Two boys use a rubber tube to float in a flooded street in Bangladesh
Catastrophic floods in Bangladesh were among many disasters that occurred in the last three months.
EPA/Monirul Alam

In China the figure was 63 million, with daily rainfall records set across the country. China’s Three Gorges Hydroelectric Dam, the world’s biggest, received the largest inflow of water in its history, prompting fears last week the dam would be breached.

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In southern Japan, record-setting rains that dumped 1,000 millimetres of water in just three days forced hundreds of thousands of people from their homes.

Then, earlier this month, deadly fires erupted across California, exacerbated by persistent drought and record-setting temperatures. In just five days, the fires burned more land in the state than was destroyed in all of 2019.

We can’t ignore climate change

While it’s difficult to scientifically demonstrate that climate change “causes” any one disaster, the general direction is crystal clear. As the climate continues to warm, the frequency and severity of these events will increase.

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We’re already seeing worrying signs of this in Queensland, our most hazard-prone state. Over the past three years, 53 of Queensland’s 77 local government areas have endured three or more major disasters. And 71 out of 77 local government areas have experienced two or more such events.

These communities are increasingly in the unsustainable situation of chronically recovering from disasters.

The prime minister has argued “Australia, on its own, cannot control the world’s climate, as Australia accounts for just 1.3% of global emissions”.

But because we’re disproportionately vulnerable to the threats of climate change, it’s imperative we convince other nations to reduce their greenhouse gas emissions.

Our international advocacy will only be credible if we strengthen our own ambition to mitigate climate change. And as the government prepares to submit its updated targets under the Paris Climate Agreement, a recommendation to reduce emissions from the royal commission would be appropriate and extremely useful.The Conversation

Robert Glasser, Visiting Fellow, Australian National University

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

Dishing the dirt: Australia’s move to store carbon in soil is a problem for tackling climate change


Robert Edwin White, University of Melbourne and Brian Davidson, University of Melbourne

To slow climate change, humanity has two main options: reduce greenhouse gas emissions directly or find ways to remove them from the atmosphere. On the latter, storing carbon in soil – or carbon farming – is often touted as a promising way to offset emissions from other sources such as energy generation, industry and transport.

The Morrison government’s Technology Investment Roadmap, now open for public comment, identifies soil carbon as a potential way to reduce emissions from agriculture and to offset other emissions.

In particular, it points to so-called “biochar” – plant material transformed into carbon-rich charcoal then applied to soil.

But the government’s plan contains misconceptions about both biochar, and the general effectiveness of soil carbon as an emissions reduction strategy.

Emissions rising from a coal plant.
Soil carbon storage is touted as a way to offset emissions from industry and elsewhere.

What is biochar?

Through photosynthesis, plants turn carbon dioxide (CO₂) into organic material known as biomass. When that biomass decomposes in soil, CO₂ is produced and mostly ends up in the atmosphere.

This is a natural process. But if we can intervene by using technology to keep carbon in the soil rather than in the atmosphere, in theory that will help mitigate climate change. That’s where biochar comes in.

Making biochar involves heating waste organic materials in a reduced-oxygen environment to create a charcoal-like product – a process called “pyrolysis”. The carbon from the biomass is stored in the charcoal, which is very stable and does not decompose for decades.

Plant materials are the predominant material or “feedstock” used to make biochar, but livestock manure can also be used. The biochar is applied to the soil, purportedly to boost soil fertility and productivity. This has been tested on grassland, cropping soils and in vineyards.

A handful of biochar.
Biochar is produced by burning organic material in a low oxygen environment.

But there’s a catch

So far, so good. But there are a few downsides to consider.

First, the pyrolysis process produces combustible gases and uses energy – to the extent that when all energy inputs and outputs are considered in a life cycle analysis, the net energy balance can be negative. In other words, the process can create more greenhouse gas emissions than it saves. The balance depends on many factors including the type and condition of the feedstock and the rate and temperature of pyrolysis.

Second, while biochar may improve the soil carbon status at a new site, the sites from which the carbon residues are removed, such as farmers’ fields or harvested forests, will be depleted of soil carbon and associated nutrients. Hence there may be no overall gain in soil fertility.

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Third, the government roadmap claims increasing soil carbon can reduce emissions from livestock farming while increasing productivity. Theoretically, increased soil carbon should lead to better pasture growth. But the most efficient way for farmers to take advantage of the growth, and increase productivity, is to keep more livestock per hectare.

Livestock such as cows and sheep produce methane – a much more potent greenhouse gas than carbon dioxide. Our analysis suggests the methane produced by the extra stock would exceed the offsetting effect of storing more soil carbon. This would lead to a net increase, not decrease, in greenhouse gas

Beef cattle grazing in a field
Farmers would have to increase stock numbers to benefit from pasture growth.
Dan Peled/AAP

A policy failure

The government plan refers to the potential to build on the success of the Emissions Reduction Fund. Among other measures, the fund pays landholders to increase the amount of carbon stored in soil through carbon credits issued through the Carbon Farming Initiative.

However since 2014, the Emissions Reduction Fund has not significantly reduced Australia’s greenhouse gas emissions – and agriculture’s contribution has been smaller still.

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So far, the agriculture sector has been contracted to provide about 9.5% of the overall abatement, or about 18.3 million tonnes. To date, it’s supplied only 1.54 million tonnes – 8.4% of the sector’s commitment.

The initiative has largely failed because several factors have made it uneconomic for farmers to take part. They include:

  • overly complex regulations
  • requirements for expensive soil sampling and analysis
  • the low value of carbon credits (averaging $12 per tonne of CO₂-equivalent since the scheme began).
A farmer inspecting crops.
For many farmers, taking part in the Emissions Reduction Fund is uneconomic.

A misguided strategy

We believe the government is misguided in considering soil carbon as an emissions reduction technology.

Certainly, increasing soil carbon at one location can boost soil fertility and potentially productivity, but these are largely private landholder benefits – paid for by taxpayers in the form of carbon credits.

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If emissions reduction is seen as a public benefit, then the payment to farmers becomes a subsidy. But it’s highly questionable whether the public benefit (in the form of reduced emissions) is worth the cost. The government has not yet done this analysis.

To be effective, future emissions technology in Australia should focus on improving energy efficiency in industry, the residential sector and transport, where big gains are to be made.The Conversation

Robert Edwin White, Professor Emeritus, University of Melbourne and Brian Davidson, Senior Lecturer, Department of Agriculture and Food Systems, University of Melbourne

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

Carbon dioxide levels over Australia rose even after COVID-19 forced global emissions down. Here’s why


Zoe Loh, CSIRO; Helen Cleugh, CSIRO; Paul Krummel, CSIRO, and Ray Langenfelds, CSIRO

COVID-19 has curtailed the activities of millions of people across the world and with it, greenhouse gas emissions. As climate scientists at the Cape Grim Baseline Air Pollution Station, we are routinely asked: does this mean carbon dioxide concentrations in the atmosphere have fallen?

The answer, disappointingly, is no. Throughout the pandemic, atmospheric carbon dioxide (CO₂) levels continued to rise.

In fact, our measurements show more CO₂ accumulated in the atmosphere between January and July 2020 than during the same period in 2017 or 2018.

Emissions from last summer’s bushfires may have contributed to this. But there are several other reasons why COVID-19 has not brought CO₂ concentrations down at Cape Grim – let’s take a look at them.

Measuring the cleanest air in the world

Cape Grim is on the northwest tip of Tasmania. Scientists at the station, run by the CSIRO and Bureau of Meteorology, have monitored and studied the global atmosphere for the past 44 years.

The air we monitor is the cleanest in the world when it blows from the southwest, off the Southern Ocean. Measurements taken during these conditions are known as “baseline concentrations”, and represent the underlying level of carbon dioxide in the Southern Hemisphere’s atmosphere.

The Cape Grim station
The Cape Grim station measures the cleanest air in the world.
Bureau of Meteorology

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A drop in the CO₂ ocean

Emissions reductions due to COVID-19 started in China in January, and peaked globally in April. Our measurements show atmospheric CO₂ levels rose during that period. In January 2020, baseline CO₂ was 408.3 parts per million (ppm) at Cape Grim. By July that had risen to 410 ppm.

Since the station first began measurements in 1976, carbon dioxide levels in the atmosphere have increased by 25%, as shown in the graph below. The slowdown in the rate of carbon emissions during the pandemic is a mere tug against this overall upward trend.

The CO₂ increase is due to the burning of fossil fuels for energy, and land use change such as deforestation which leaves fewer trees to absorb CO₂ from the air, and changes the uptake and release of carbon in the soils.

Baseline CO₂ record from Cape Grim.
Baseline CO₂ record from Cape Grim.
Author provided

Atmospheric transport

Large air circulation patterns in the atmosphere spread gases such as CO₂ around the world, but this process takes time.

Most emissions reduction due to COVID-19 occurred in the Northern Hemisphere, because that’s where most of the world’s population lives. Direct measurements of CO₂ in cities where strict lockdown measures were imposed show emissions reductions of up to 75%. This would have reduced atmospheric CO₂ concentrations locally.

But it will take many months for this change to manifest in the Southern Hemisphere atmosphere – and by the time it does, the effect will be significantly diluted.

Natural ups and downs

Emissions reductions during COVID-19 are a tiny component of a very large carbon cycle. This cycle is so dynamic that even when the emissions slowdown is reflected in atmospheric CO₂ levels, the reduction will be well within the cycle’s natural ebb and flow.

Here’s why. Global carbon emissions have grown by about 1% a year over the past decade. This has triggered growth in atmospheric CO₂ levels of between 2 and 3 ppm per year in that time, as shown in the graph below. In fact, since our measurements began, CO₂ has accumulated more rapidly in the atmosphere with every passing decade, as emissions have grown.

Annual growth in CO₂ at Cape Grim  since 1976. Red horizontal bars show the average growth rate in ppm/year each decade.
Annual growth in CO₂ at Cape Grim since 1976. Red horizontal bars show the average growth rate in ppm/year each decade.
Author provided

But although CO₂ emissions have grown consistently, the resulting rate of accumulation in the atmosphere varies considerably each year. This is because roughly half of human emissions are mopped up by ecosystems and the oceans, and these processes change from year to year.

For example, in southeast Australia, last summer’s extensive and prolonged bushfires emitted unusually large amounts of CO₂, as well as changing the capacity of ecosystems to absorb it. And during strong El Niño events, reduced rainfall in some regions limits the productivity of grasslands and forests, so they take up less CO₂.

The graph below visualises this variability. It shows the baseline CO₂ concentrations for each year, relative to January 1. Note how the baseline level changes through a natural seasonal cycle, how that change varies from year to year and how much CO₂ has been added to the atmosphere by the end of the year.

Daily baseline values for CO₂ for each year from 1977 relative to 1 January for that year
Daily baseline values for CO2 for each year from 1977 relative to 1 January for that year.
Author provided

The growth rate has been as much as 3 ppm per year. The black line represents 2020 and lines for the preceding five years are coloured. All show recent annual growth rates of about 2-3 ppm/year – a variability in the range of about 1 ppm/year.

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Research in May estimated that due to the COVID-19 lockdowns, global annual average emissions for 2020 would be between 4.2% and 7.5% lower than for 2019.

Let’s simplistically assume CO₂ concentration growth reduces by the same amount. There would be 0.08-0.23 ppm less CO₂ in the atmosphere by the end of 2020 than if no pandemic occurred. This variation is well within the natural 1 ppm/year annual variability in CO₂ growth.

CO₂ is released in industrial emissions
CO₂ levels in the atmosphere are increasing due to fossil fuel burning and land use change.

The road ahead

It’s clear COVID-19 has not solved the climate change problem. But this fact helps us understand the magnitude of change required if we’re to stabilise the global climate system.

The central aim of the Paris climate agreement is to limit global warming to well below 2℃, and pursue efforts to keep it below 1.5℃. To achieve this, global CO₂ emissions must decline by 3% and 7% each year, respectively, until 2030, according to the United Nations Emissions Gap Report.

Thanks to COVID-19, we may achieve this reduction in 2020. But to lock in year-on-year emissions reductions that will be reflected in the atmosphere, we must act now to make deep, significant and permanent changes to global energy and economic systems.

The lead author, Zoe Loh, discusses the CO₂ record from Cape Grim in Fight for Planet A, showing now on the ABC.

Read more:
Why there’s more greenhouse gas in the atmosphere than you may have realised

The Conversation

Zoe Loh, Senior Research Scientist, CSIRO; Helen Cleugh, Senior research scientist, CSIRO Climate Science Centre, CSIRO; Paul Krummel, Research Group Leader, CSIRO, and Ray Langenfelds, Scientist at CSIRO Atmospheric Research, CSIRO

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

Climate explained: are we doomed if we don’t manage to curb emissions by 2030?

Thongden Studio/Shutterstock

Robert McLachlan, Massey University


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

Is humanity doomed? If in 2030 we have not reduced emissions in a way that means we stay under say 2℃ (I’ve frankly given up on 1.5℃), are we doomed then?

Humanity is not doomed, not now or even in a worst-case scenario in 2030. But avoiding doom — either the end or widespread collapse of civilisation — is setting a pretty low bar. We can aim much higher than that without shying away from reality.

It’s right to focus on global warming of 1.5℃ and 2℃ in the first instance. The many manifestations of climate change — including heat waves, droughts, water stress, more intense storms, wildfires, mass extinction and warming oceans — all get progressively worse as the temperature rises.

Climate scientist Michael Mann uses the metaphor of walking into an increasingly dense minefield.

Good reasons not to give up just yet

The Intergovernmental Panel on Climate Change described the effects of a 1.5℃ increase in average temperatures in a special report last year. They are also nicely summarised in an article about why global temperatures matter, produced by NASA.

The global average temperature is currently about 1.2℃ higher than what it was at the time of the Industrial Revolution, some 250 years ago. We are already witnessing localised impacts, including the widespread coral bleaching on Australia’s Great Barrier Reef.

This graph shows different emission pathways and when the world is expected to reach global average temperatures of 1.5℃ or 2℃ above pre-industrial levels.
Global Carbon Project, Author provided

Limiting warming to 1.5℃ requires cutting global emissions by 7.6% each year this decade. This does sound difficult, but there are reasons for optimism.

Read more:
The climate won’t warm as much as we feared – but it will warm more than we hoped

First, it’s possible technically and economically. For example, the use of wind and solar power has grown exponentially in the past decade, and their prices have plummeted to the point where they are now among the cheapest sources of electricity. Some areas, including energy storage and industrial processes such as steel and cement manufacture, still need further research and a drop in price (or higher carbon prices).

Second, it’s possible politically. Partly in response to the Paris Agreement, a growing number of countries have adopted stronger targets. Twenty countries and regions (including New Zealand and the European Union) are now targeting net zero emissions by 2050 or earlier.

A recent example of striking progress comes from Ireland – a country with a similar emissions profile to New Zealand. The incoming coalition’s “programme for government” includes emission cuts of 7% per year and a reduction by half by 2030.

Read more:
Young people won’t accept inaction on climate change, and they’ll be voting in droves

Third, it’s possible socially. Since 2019, we have seen the massive growth of the School Strike 4 Climate movement and an increase in fossil fuel divestment. Several media organisations, including The Conversation, have made a commitment to evidence-based coverage of climate change and calls for a Green New Deal are coming from a range of political parties, especially in the US and Europe.

There is also a growing understanding that to ensure a safe future we need to consume less overall. If these trends continue, then I believe we can still stay below 1.5℃.

The pessimist perspective

Now suppose we don’t manage that. It’s 2030 and emissions have only fallen a little bit. We’re staring at 2℃ in the second half of the century.

At 2℃ of warming, we could expect to lose more than 90% of our coral reefs. Insects and plants would be at higher risk of extinction, and the number of dangerously hot days would increase rapidly.

Read more:
Not convinced on the need for urgent climate action? Here’s what happens to our planet between 1.5°C and 2°C of global warming

The challenges would be exacerbated and we would have new issues to consider. First, under the “shifting baseline” phenomenon — essentially a failure to notice slow change and to value what is already lost — people might discount the damage already done. Continuously worsening conditions might become the new normal.

Second, climate impacts such as mass migration could lead to a rise of nationalism and make international cooperation harder. And third, we could begin to pass unpredictable “tipping points” in the Earth system. For example, warming of more than 2°C could set off widespread melting in Antarctica, which in turn would contribute to sea level rise.

Read more:
If warming exceeds 2°C, Antarctica’s melting ice sheets could raise seas 20 metres in coming centuries

But true doom-mongers tend to assume a worst-case scenario on virtually every area of uncertainty. It is important to remember that such scenarios are not very likely.

While bad, this 2030 scenario doesn’t add up to doom — and it certainly doesn’t change the need to move away from fossil fuels to low-carbon options.The Conversation

Robert McLachlan, Professor in Applied Mathematics, Massey University

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

Carbon emissions are chilling the atmosphere 90km above Antarctica, at the edge of space

Ashleigh Wilson

John French, University of Tasmania; Andrew Klekociuk, University of Tasmania, and Frank Mulligan, National University of Ireland Maynooth

While greenhouse gases are warming Earth’s surface, they’re also causing rapid cooling far above us, at the edge of space. In fact, the upper atmosphere about 90km above Antarctica is cooling at a rate ten times faster than the average warming at the planet’s surface.

Our new research has precisely measured this cooling rate, and revealed an important discovery: a new four-year temperature cycle in the polar atmosphere. The results, based on 24 years of continuous measurements by Australian scientists in Antarctica, were published in two papers this month.

The findings show Earth’s upper atmosphere, in a region called the “mesosphere”, is extremely sensitive to rising greenhouse gas concentrations. This provides a new opportunity to monitor how well government interventions to reduce emissions are working.

Our project also monitors the spectacular natural phenomenon known as “noctilucent” or “night shining” clouds. While beautiful, the more frequent occurrence of these clouds is considered a bad sign for climate change.

Studying the ‘airglow’

Since the 1990s, scientists at Australia’s Davis research station have taken more than 600,000 measurements of the temperatures in the upper atmosphere above Antarctica. We’ve done this using sensitive optical instruments called spectrometers.

These instruments analyse the infrared glow radiating from so-called hydroxyl molecules, which exist in a thin layer about 87km above Earth’s surface. This “airglow” allows us to measure the temperature in this part of the atmosphere.

Scientific equipment
Spectrometer in the optical laboratory at Davis station, Antarctica.
John French

Our results show that in the high atmosphere above Antarctica, carbon dioxide and other greenhouse gases do not have the warming effect they do in the lower atmosphere (by colliding with other molecules). Instead the excess energy is radiated to space, causing a cooling effect.

Our new research more accurately determines this cooling rate. Over 24 years, the upper atmosphere temperature has cooled by about 3℃, or 1.2℃ per decade. That is about ten times greater than the average warming in the lower atmosphere – about 1.3℃ over the past century.

Untangling natural signals

Rising greenhouse gas emissions are contributing to the temperature changes we recorded, but a number of other influences are also at play. These include the seasonal cycle (warmer in winter, colder in summer) and the Sun’s 11-year activity cycle (which involves quieter and more intense solar periods) in the mesosphere.

One challenge of the research was untangling all these merged “signals” to work out the extent to which each was driving the changes we observed.

Surprisingly in this process, we discovered a new natural cycle not previously identified in the polar upper atmosphere. This four-year cycle which we called the Quasi-Quadrennial Oscillation (QQO), saw temperatures vary by 3-4℃ in the upper atmosphere.

Discovering this cycle was like stumbling across a gold nugget in a well-worked claim. More work is needed to determine its origin and full importance.

But the finding has big implications for climate modelling. The physics that drive this cycle are unlikely to be included in global models currently used to predict climate change. But a variation of 3-4℃ every four years is a large signal to ignore.

We don’t yet know what’s driving the oscillation. But whatever the answer, it also seems to affect the winds, sea surface temperatures, atmospheric pressure and sea ice concentrations around Antarctica.

‘Night shining’ clouds

Our research also monitors how cooling temperatures are affecting the occurrence of noctilucent or “night shining” clouds.

Noctilucent clouds are very rare – from Australian Antarctic stations we’ve recorded about ten observations since 1998. They occur at an altitude of about 80km in the polar regions during summer. You can only see them from the ground when the sun is below the horizon during twilight, but still shining on the high atmosphere.

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Humans are encroaching on Antarctica’s last wild places, threatening its fragile biodiversity

The clouds appear as thin, pale blue, wavy filaments. They are comprised of ice crystals and require temperatures around minus 130℃ to form. While impressive, noctilucent clouds are considered a “canary in the coalmine” of climate change. Further cooling of the upper atmosphere as a result of greenhouse gas emissions will likely lead to more frequent noctilucent clouds.

There is already some evidence the clouds are becoming brighter and more widespread in the Northern Hemisphere.

Sea ice in Antarctica
The new temperature cycle is reflected in the concentration of sea ice in Antacrtica.
John French

Measuring change

Human-induced climate change threatens to alter radically the conditions for life on our planet. Over the next several decades – less than one lifetime – the average global air temperature is expected to increase, bringing with it sea level rise, weather extremes and changes to ecosystems across the world.

Long term monitoring is important to measure change and test and calibrate ever more complex climate models. Our results contribute to a global network of observations coordinated by the Network for Detection of Mesospheric Change for this purpose.

The accuracy of these models is critical to determining whether government and other interventions to curb climate change are indeed effective.

Read more:
Anatomy of a heatwave: how Antarctica recorded a 20.75°C day last month

The Conversation

John French, Atmospheric physicist, University of Tasmania; Andrew Klekociuk, Principal Research Scientist, Australian Antarctic Division and Adjunct Senior Lecturer, University of Tasmania, and Frank Mulligan, , National University of Ireland Maynooth

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

Emissions of methane – a greenhouse gas far more potent than carbon dioxide – are rising dangerously

Sukree Sukplang/Reuters

Pep Canadell, CSIRO; Ann Stavert; Ben Poulter, NASA; Marielle Saunois, Université de Versailles Saint-Quentin-en-Yvelines (UVSQ) – Université Paris-Saclay ; Paul Krummel, CSIRO, and Rob Jackson, Stanford University

Fossil fuels and agriculture are driving a dangerous acceleration in methane emissions, at a rate consistent with a 3-4℃ rise in global temperatures this century.

Our two papers published today provide a troubling report card on the global methane budget, and explore what it means for achieving the Paris Agreement target of limiting warming to well below 2℃.

Methane concentration in the atmosphere reached 1,875 parts per billion at the end of 2019 – more than two and a half times higher than pre-industrial levels.

Once emitted, methane stays in the atmosphere for about nine years – a far shorter period than carbon dioxide. However its global warming potential is 86 times higher than carbon dioxide when averaged over 20 years and 28 times higher over 100 years.

In Australia, methane emissions from fossil fuels are rising due to expansion of the natural gas industry, while agriculture emissions are falling.

Agriculture and fossil fuels are driving the rise in methane emissions.

Balancing the global methane budget

We produced a methane “budget” in which we tracked both methane sources and sinks. Methane sources include human activities such as agriculture and burning fossil fuels, as well as natural sources such as wetlands. Sinks refer to the destruction of methane in the atmosphere and soils.

Our data show methane emissions grew almost 10% from the decade of 2000-2006 to the most recent year of the study, 2017.

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Atmospheric methane is increasing by around 12 parts per billion each year – a rate consistent with a scenario modelled by the Intergovernmental Panel on Climate Change under which Earth warms by 3-4℃ by 2100.

From 2008-2017, 60% of methane emissions were man-made. These include, in order of contribution:

  • agriculture and waste, particularly emissions from ruminant animals (livestock), manure, landfills, and rice farming
  • the production and use of fossil fuels, mainly from the oil and gas industry, followed by coal mining
  • biomass burning, from wood burning for heating, bushfires and burning biofuels.
2000 years of atmospheric methane concentrations. Observations taken from ice cores and atmosphere. Source: BoM/CSIRO/AAD.

The remaining emissions (40%) come from natural sources. In order of contribution, these include:

  • wetlands, mostly in tropical regions and cold parts of the planet such as Siberia and Canada
  • lakes and rivers
  • natural geological sources on land and oceans such as gas–oil seeps and mud volcanoes
  • smaller sources such as tiny termites in the savannas of Africa and Australia.

So what about the sinks? Some 90% of methane is ultimately destroyed, or oxidised, in the lower atmosphere when it reacts with hydroxyl radicals. The rest is destroyed in the higher atmosphere and in soils.

Increasing methane concentrations in the atmosphere could, in part, be due to a decreasing rate of methane destruction as well as rising emissions. However, our findings don’t suggest this is the case.

Measurements show that methane is accumulating in the atmosphere because human activity is producing it at a much faster rate than it’s being destroyed.

NASA video showing sources of global methane.

Source of the problem

The biggest contributors to the methane increase were regions at tropical latitudes, such as Brazil, South Asia and Southeast Asia, followed by those at the northern-mid latitude such as the US, Europe and China.

In Australia, agriculture is the biggest source of methane. Livestock are the predominant cause of emissions in this sector, which have declined slowly over time.

The fossil fuel industry is the next biggest contributor in Australia. Over the past six years, methane emissions from this sector have increased due to expansion of the natural gas industry, and associated “fugitive” emissions – those that escape or are released during gas production and transport.

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Tropical emissions were dominated by increases in the agriculture and waste sector, whereas northern-mid latitude emissions came mostly from burning fossil fuels. When comparing global emissions in 2000-2006 to those in 2017, both agriculture and fossil fuels use contributed equally to the emissions growth.

Since 2000, coal mining has contributed most to rising methane emissions from the fossil fuel sector. But the natural gas industry’s rapid growth means its contribution is growing.

Some scientists fear global warming will cause carbon-rich permafrost (ground in the Arctic that is frozen year-round) to thaw, releasing large amounts of methane.

But in the northern high latitudes, we found no increase in methane emissions between the last two decades. There are several possible explanations for this. Improved ground, aerial and satellite surveys are needed to ensure emissions in this vast region are not being missed.

More surveys are needed into thawing permafrost in the high northern latitudes.

Fixing our methane leaks

Around the world, considerable research and development efforts are seeking ways to reduce methane emissions. Methods to remove methane from the atmosphere are also being explored.

Europe shows what’s possible. There, our research shows methane emissions have declined over the past two decades – largely due to agriculture and waste policies which led to better managing of livestock, manure and landfill.

Livestock produce methane as part of their digestive process. Feed additives and supplements can reduce these emissions from ruminant livestock. There is also research taking place into selective breeding for low emissions livestock.

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The extraction, processing and transport of fossil fuels contributes to substantial methane emissions. But “super-emitters” – oil and gas sites that release a large volume of methane – contribute disproportionately to the problem.

This skewed distribution presents opportunities. Technology is available that would enable super-emitters to significantly reduce emissions in a very cost effective way.

Clearly, current upward trends in methane emissions are incompatible with meeting the goals of the Paris climate agreement. But methane’s short lifetime in the atmosphere means any action taken today would bring results in just nine years. That provides a huge opportunity for rapid climate change mitigation.The Conversation

Pep Canadell, Chief research scientist, CSIRO Oceans and Atmosphere; and Executive Director, Global Carbon Project, CSIRO; Ann Stavert, Project Scientist; Ben Poulter, Research scientist, NASA; Marielle Saunois, Enseignant-chercheur, Laboratoire des sciences du climat et de l’environnement (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ) – Université Paris-Saclay ; Paul Krummel, Research Group Leader, CSIRO, and Rob Jackson, Chair, Department of Earth System Science, and Chair of the Global Carbon Project,, Stanford University

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

Climate explained: what if we took all farm animals off the land and planted crops and trees instead?

Kira Volkov/Shutterstock

Sebastian Leuzinger, Auckland University of Technology


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

I would like to know how much difference we could make to our commitment under the Paris Agreement and our total greenhouse gas emissions if we removed all cows and sheep from the country and grew plants in their place (hemp, wheat, oats etc). Surely we could easily become carbon neutral if we removed all livestock? How much more oxygen would be produced from plants growing instead? How would this offset our emissions? And what if we returned the land the animals were on to native forests or even pine plantations?

This is an interesting question and gives me the opportunity for some nice – albeit partly unrealistic – model calculations. Before I start, just two comments regarding the question itself.

Oxygen concentrations have been relatively stable at around 21% of the air we breathe for millions of years. This will not change markedly even if carbon dioxide emissions increase for years to come. Carbon dioxide concentrations, even in the most pessimistic emissions scenarios, will only get to around 0.1% of the atmosphere, hardly affecting the air’s oxygen content.

Secondly, grazing animals like cows and sheep emit methane — and that’s what harms the climate, not the grassland itself. Hemp or wheat plantations would have a similar capacity to take up carbon dioxide as grassland. But growing trees is what makes the difference.

Read more:
Climate explained: how different crops or trees help strip carbon dioxide from the air

Here’s a back-of-the-envelope calculation to work out how New Zealand’s carbon balance would change if all livestock were removed and all agricultural land converted to forest.

If New Zealand stopped farming cows and sheep, it would remove methane emissions.
Heath Johnson/Shutterstock

Converting pasture to trees

This would remove all methane emissions from grazing animals (about 40 megatonnes of carbon dioxide equivalent per year).

New Zealand has about 10 million hectares of grassland. Let us assume that mature native bush or mature pine forests store the equivalent of roughly 1,000 tonnes of carbon dioxide per hectare.

If it takes 250 years to grow mature native forests on all former agricultural land, this would lock away 10 billion tonnes of carbon dioxide within that time span, offsetting our carbon dioxide emissions (energy, waste and other smaller sources) during the 250 years of regrowth. Because pine forest grows faster, we would overcompensate for our emissions until the forest matures (allow 50 years for this), creating a net carbon sink.

Note these calculations are based on extremely crude assumptions, such as linear growth, absence of fire and other disturbances, constant emissions (our population will increase, and so will emissions), ignorance of soil processes, and many more.

If agricultural land was used to grow crops, we would save the 40 megatonnes of carbon dioxide equivalent emitted by livestock in the form of methane, but we would not store a substantial amount of carbon per hectare.

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Steps towards a carbon-neutral New Zealand

How should we interpret this rough estimate? First, we must acknowledge even with our best intentions, we still need to eat, and converting all agricultural land to forest would leave us importing food from overseas — certainly not great for the global carbon budget.

Second, it shows if livestock numbers were at least reduced, and we all turned to a more plant-based diet, we could reduce our emissions substantially. The effect would be similar to reforesting large parts of the country.

Third, this example also shows that eventually, be it after 250 years in the case of growing native forests, or after about 50 years in the case of pine forests, our net carbon emissions would be positive again. As the forests mature, carbon stores are gradually replenished and our emissions would no longer be compensated. Mature forests eventually become carbon neutral.

Even though the above calculations are coarse, this shows that a realistic (and quick) way to a carbon-neutral New Zealand will likely involve three steps: reduction of emissions (both in the agricultural and energy sectors), reforestation (both native bush and fast growing exotics), and a move to a more plant-based diet.The Conversation

Sebastian Leuzinger, Professor, Auckland University of Technology

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