Earth may temporarily pass dangerous 1.5℃ warming limit by 2024, major new report says


Pep Canadell, CSIRO and Rob Jackson, Stanford University

The Paris climate agreement seeks to limit global warming to 1.5℃ this century. A new report by the World Meteorological Organisation warns this limit may be exceeded by 2024 – and the risk is growing.

This first overshoot beyond 1.5℃ would be temporary, likely aided by a major climate anomaly such as an El Niño weather pattern. However, it casts new doubt on whether Earth’s climate can be permanently stabilised at 1.5℃ warming.

This finding is among those just published in a report titled United in Science. We contributed to the report, which was prepared by six leading science agencies, including the Global Carbon Project.

The report also found while greenhouse gas emissions declined slightly in 2020 due to the COVID-19 pandemic, they remained very high – which meant atmospheric carbon dioxide concentrations have continued to rise.

Woman holds a sign at a climate protest
The world may exceed the 1.5℃ warming threshold sooner than we expected.
Erik Anderson/AAP

Greenhouse gases rise as CO₂ emissions slow

Concentrations of the three main greenhouse gases – carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O), have all increased over the past decade. Current concentrations in the atmosphere are, respectively, 147%, 259% and 123% of those present before the industrial era began in 1750.

Concentrations measured at Hawaii’s Mauna Loa Observatory and at Australia’s Cape Grim station in Tasmania show concentrations continued to increase in 2019 and 2020. In particular, CO₂ concentrations reached 414.38 and 410.04 parts per million in July this year, respectively, at each station.

Atmospheric concentrations of carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂0) from WMO Global Atmosphere Watch.

Growth in CO₂ emissions from fossil fuel use slowed to around 1% per year in the past decade, down from 3% during the 2000s. An unprecedented decline is expected in 2020, due to the COVID-19 economic slowdown. Daily CO₂ fossil fuel emissions declined by 17% in early April at the peak of global confinement policies, compared with the previous year. But by early June they had recovered to a 5% decline.

We estimate a decline for 2020 of about 4-7% compared to 2019 levels, depending on how the pandemic plays out.

Although emissions will fall slightly, atmospheric CO₂ concentrations will still reach another record high this year. This is because we’re still adding large amounts of CO₂ to the atmosphere.

Global daily fossil CO₂ emissions to June 2020. Updated from Le Quéré et al. 2020, Nature Climate Change.

Warmest five years on record

The global average surface temperature from 2016 to 2020 will be among the warmest of any equivalent period on record, and about 0.24℃ warmer than the previous five years.

This five-year period is on the way to creating a new temperature record across much of the world, including Australia, southern Africa, much of Europe, the Middle East and northern Asia, areas of South America and parts of the United States.




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Sea levels rose by 3.2 millimetres per year on average over the past 27 years. The growth is accelerating – sea level rose 4.8 millimetres annually over the past five years, compared to 4.1 millimetres annually for the five years before that.

The past five years have also seen many extreme events. These include record-breaking heatwaves in Europe, Cyclone Idai in Mozambique, major bushfires in Australia and elsewhere, prolonged drought in southern Africa and three North Atlantic hurricanes in 2017.

Left: Global average temperature anomalies (relative to pre-industrial) from 1854 to 2020 for five data sets. UK-MetOffice. Right: Average sea level for the period from 1993 to July 16, 2020. European Space Agency and Copernicus Marine Service.

1 in 4 chance of exceeding 1.5°C warming

Our report predicts a continuing warming trend. There is a high probability that, everywhere on the planet, average temperatures in the next five years will be above the 1981-2010 average. Arctic warming is expected to be more than twice that the global average.

There’s a one-in-four chance the global annual average temperature will exceed 1.5℃ above pre-industrial levels for at least one year over the next five years. The chance is relatively small, but still significant and growing. If a major climate anomaly, such as a strong El Niño, occurs in that period, the 1.5℃ threshold is more likely to be crossed. El Niño events generally bring warmer global temperatures.

Under the Paris Agreement, crossing the 1.5℃ threshold is measured over a 30-year average, not just one year. But every year above 1.5℃ warming would take us closer to exceeding the limit.

Global average model prediction of near surface air temperature relative to 1981–2010. Black line = observations, green = modelled, blue = forecast. Probability of global temperature exceeding 1.5℃ for a single month or year shown in brown insert and right axis. UK Met Office.

Arctic Ocean sea-ice disappearing

Satellite records between 1979 and 2019 show sea ice in the Arctic summer declined at about 13% per decade, and this year reached its lowest July levels on record.

In Antarctica, summer sea ice reached its lowest and second-lowest extent in 2017 and 2018, respectively, and 2018 was also the second-lowest winter extent.

Most simulations show that by 2050, the Arctic Ocean will practically be free of sea ice for the first time. The fate of Antarctic sea ice is less certain.

A polar bear on an ice floe
Summer sea ice in the Arctic is expected to virtually disappear by 2050.
Zaruba Ondrej/AP

Urgent action can change trends

Human activities emitted 42 billion tonnes of CO₂ in 2019 alone. Under the Paris Agreement, nations committed to reducing emissions by 2030.

But our report shows a shortfall of about 15 billion tonnes of CO₂ between these commitments, and pathways consistent with limiting warming to well below 2℃ (the less ambitious end of the Paris target). The gap increases to 32 billion tonnes for the more ambitious 1.5℃ goal.

Our report models a range of climate outcomes based on various socioeconomic and policy scenarios. It shows if emission reductions are large and sustained, we can still meet the Paris goals and avoid the most severe damage to the natural world, the economy and people. But worryingly, we also have time to make it far worse.




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



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


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


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.

‘Compassionate conservation’: just because we love invasive animals, doesn’t mean we should protect them



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Kaya Klop-Toker, University of Newcastle; Alex Callen, University of Newcastle; Andrea Griffin, University of Newcastle; Matt Hayward, University of Newcastle, and Robert Scanlon, University of Newcastle

On an island off the Queensland coast, a battle is brewing over the fate of a small population of goats.

The battle positions the views of some conservation scientists and managers who believe native species must be protected from this invasive fauna, against those of community members who want to protect the goat herd to which they feel emotionally connected. Similar battles colour the management decisions around brumbies in Kosciuszko National Park and cats all over Australia.




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These debates show the impact of a new movement called “compassionate conservation”. This movement aims to increase levels of compassion and empathy in the management process, finding conservation solutions that minimise harm to wildlife. Among their ideas, compassionate conservationists argue no animal should be killed in the name of conservation.

But preventing extinctions and protecting biodiversity is unlikely when emotion, rather than evidence, influence decisions. As our recent paper argues, the human experience of compassion and empathy is fraught with inherent biases. This makes these emotions a poor compass for deciding what conservation action is right or wrong.

It sounds good on paper

We are facing a biological crisis unparalleled in human history, with at least 25% of the world’s assessed species at risk of extinction. These trends are particularly bad in Australia, where we have one of the world’s worst extinction records and the world’s highest rate of mammal extinctions.

The federal government recently announced it will commit to a new ten-year threatened species strategy, focused on eradicating feral pests such as foxes and cats.




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This approach goes against the principles underpinning compassionate conservation. The movement, which first emerged in 2010, is founded on the ideals of “first do no harm” and “individuals matter”.

When you first think about it, this idea sounds great. Why kill some animals to save others?

Well, invasive animals — those either intentionally or accidentally moved to a new location — are one of the biggest threats to global biodiversity.

Invasive predators, such as cats and foxes, have caused the extinction of 142 vertebrate species worldwide. In Australia, feral and domestic cats kill more than 15 billion native animals per year.

Fortunately, endangered populations can recover when these pests are removed. Controlling pest numbers is one of the most effective tools available to conservationists.

Conflicting moral standpoints

Killing pests is at stark odds with the “do no harm” values promoted by the compassionate conservation movement.

Thousands of wild horses are rapidly degrading the ecosystems of Australia’s high country.

Compassionate conservationists argue it’s morally wrong to kill animals for management, whereas conservation scientists argue it’s morally wrong to allow species to go extinct — especially if human actions (such as the movement of species to new locations) threaten extinction.

These conflicting moral standpoints result in an emotional debate about when it is justified to kill or let be killed. This argument centres on emotion and moral beliefs. There is no clear right or wrong answer and, therefore, no resolution.

In an attempt to break this emotional stalemate, we explored the biases inherent in the emotions of compassion and empathy, and questioned if increased empathy and compassion are really what conservation needs.

Evolutionary biases

At first, compassion and empathy may appear vital to conservation, and on an individual level, they probably are. People choose to work in conservation because they care for wild species. But compassion and empathy come with strong evolutionary biases.

The first bias is that people feel more empathy toward the familiar — people care more for things they relate most closely to. The second bias is failure to scale-up — we don’t feel 100 times more sorrow when hearing about 100 people dying, compared to a single person (or species).

Evolution has shaped our emotions to peak for things we relate most strongly to, and to taper off when numbers get high — most likely to protect us from becoming emotionally overloaded.

Let’s put these emotions in the context of animal management. Decisions based on empathy and compassion will undoubtedly favour charismatic, relatable species over thousands of less-familiar small, imperilled creatures.

This bias is evident in the battle over feral horses in national parks. There is public backlash over the culling of brumbies, yet there is no such response to the removal of feral pigs, despite both species having similarly negative impacts on protected habitats.

More harm than good

If compassionate conservation is adopted, culling invasive species would cease, leading to the rapid extinction of more vulnerable native species. A contentious example is the race to save the endangered Tristan albatross from introduced mice on Gough Island in the south Atlantic.

Sealers introduced mice in the 1800s, and the mice have adapted to feed on albatross chicks, killing an estimated two million birds per year. Under compassionate conservation, lethal control of the mice would not be allowed, and the albatross would be added to the extinction list within 20 years.




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What’s more, compassionate conservation advocates for a more hands-off approach to remove any harm or stress to animals. This means even the management of threatened fauna would be restricted.

Under this idea, almost all current major conservation actions would not be allowed because of temporary stress placed on individual animals. This includes translocations (moving species to safer habitat), captive breeding, zoos, radio tracking and conservation fencing.

With 15% of the world’s threatened species protected in zoos and undergoing captive breeding, a world with compassionate conservation would be one with far fewer species, and we argue, much less conservation and compassion.

In this time of biodiversity crisis and potential ecosystem collapse, we cannot afford to let emotion bias our rationale. Yes, compassion and empathy should drive people to call for more action from their leaders to protect biodiversity. But what action needs to be taken should be left to science and not our emotions.




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The Conversation


Kaya Klop-Toker, Conservation Biology Researcher, University of Newcastle; Alex Callen, Post-doctoral researcher, University of Newcastle; Andrea Griffin, Senior Lecturer, School of Psychology, University of Newcastle; Matt Hayward, Associate professor, University of Newcastle, and Robert Scanlon, PhD Candidate in Restoration Ecology, University of Newcastle

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