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



The Cape Grim observatory, home of the ‘world’s cleanest air’… and rising greenhouse gases.
CSIRO, Author provided

Zoe Loh, CSIRO; Blagoj Mitrevski, CSIRO; David Etheridge, CSIRO; Nada Derek, CSIRO; Paul Fraser, CSIRO; Paul Krummel, CSIRO; Paul Steele, CSIRO; Ray Langenfelds, CSIRO, and Sam Cleland, Australian Bureau of Meteorology

This week brought news that atmospheric carbon dioxide (CO₂) levels at the Mauna Loa atmospheric observatory in Hawaii have risen steeply for the seventh year in a row, reaching a May 2019 average of 414.7 parts per million (ppm).

It was the highest monthly average in 61 years of measurements at that observatory, and comes five years after CO₂ concentrations first breached the 400ppm milestone.

But in truth, the amount of greenhouse gas in our atmosphere is higher still. If we factor in the presence of other greenhouse gases besides carbon dioxide, we find that the world has already ticked past yet another milestone: 500ppm of what we call “CO₂-equivalent”, or CO₂-e.




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Forty years of measuring the world’s cleanest air reveals human fingerprints on the atmosphere


In July 2018, the combination of long-lived greenhouse gases measured in the “cleanest air in the world” at Cape Grim Baseline Atmospheric Pollution Station surpassed 500ppm CO₂-e.

As the atmosphere of the Southern Hemisphere contains less pollution than the north, this means the global average atmospheric concentration of greenhouse gases is now well above this level.

What is CO₂-e?

Although CO₂ is the most abundant greenhouse gas, dozens of other gases – including methane (CH₄), nitrous oxide (N₂O) and the synthetic greenhouse gases – also trap heat. Many of them are more powerful greenhouse gases than CO₂, and some linger for longer in the atmosphere. That means they have a significant influence on how much the planet is warming.

Southern Hemispheric radiative forcing relative to 1750 due to the long-lived greenhouse gases (carbon dioxide, methane, nitrous oxide and synthetic greenhouse gases), expressed as watts per square metre, from measurements in situ at Cape Grim, from the Cape Grim Air Archive, and Antarctic firn air.
CSIRO

Atmospheric scientists use CO₂-e as a convenient way to aggregate the effect of all the long-lived greenhouse gases.

As all the major greenhouse gases (CO₂, CH₄ and N₂O) are rising in concentration, so too is CO₂-e. It has climbed at an average rate of 3.3ppm per year during this decade – faster than at any time in history. And it is showing no sign of slowing.

Cape Grim/Antarctic carbon dioxide equivalent (CO₂-e) calculated from the long-lived greenhouse gas radiative forcing data shown in the figure above with CO₂ data shown for reference, annual data through to 2018. Inset panel shows the monthly mean CO₂-e data for Cape Grim from 2015 through to March 2019, showing CO₂-e surpassing 500ppm in July 2018.
CSIRO

This milestone, like so many others, is symbolic. The difference between 499 and 500ppm CO₂-e is marginal in terms of the fate of the climate and the life it sustains. But the fact that the cleanest air on the planet has now breached this threshold should elicit deep concern.

Warming on the way

The Paris climate agreement is aimed at limiting global warming to less than 2℃ above pre-industrial levels, to avoid the most dangerous effects of climate change. But the task of predicting how human greenhouse emissions will perturb the climate system on a scale of decades to centuries is complex.

The best estimate of long-term global warming expected from 500ppm CO₂-e is about 2.5℃. But so far, since pre-industrial times, the global climate (including oceans) has warmed by only 0.7℃.

This is partly because industrial smog and other tiny particles (together called aerosols) reflect sunlight out to space, offsetting some of the expected warming. What’s more, the climate system responds slowly to rising atmospheric greenhouse gas concentrations because much of the excess heat is taken up by the oceans.

The amount of heat each greenhouse gas can trap depends on its absorption spectrum – how strongly it can absorb energy at different wavelengths, particularly in the infrared range. Despite its simple molecular structure, there is still much to learn about the heat-absorbing properties of methane, the second-biggest component of CO₂-e.

Studies published in 2016 and 2018 led to the estimate of methane’s warming potential being revised upwards by 15%, meaning methane is now considered to be 32 times more efficient at trapping heat in the atmosphere than CO₂, on a per-molecule basis over a 100-year time span.

Considering this new evidence, we calculate that greenhouse gas concentrations at Cape Grim crossed the 500ppm CO₂-e threshold in July 2018.

This is higher than the official estimate based on the previous formulation for calculating CO₂-e, which remains in widespread use. For instance, the US National Oceanic and Atmospheric Administration is reporting 2018 CO₂-e as 496ppm.

The graph below shows the two curves for the time evolution of CO₂-e in the atmosphere as measured at Cape Grim, using the old and new formulae.

Cape Grim monthly CO2-e from 2015 until Sept 2018 calculated using the old and new formulae.
CSIRO

Some greenhouse gases, such as chlorofluorocarbons (CFCs), also deplete the ozone layer. CFCs are in decline thanks to the Montreal Protocol, which bans the production and use of these chemicals, despite reports that indicate some recent production of CFC-11 in China.

But unfortunately their ozone-safe replacements, hydrofluorocarbons (HFCs), are very potent greenhouse gases, and are on the rise. The recently enacted Kigali Amendment to the protocol means that consumption controls on HFCs are now in place, and this will see the growth rate of HFCs slow significantly and then reverse in the coming decades.

We can change

Australia is at the forefront of initiating measures to curb the impact of HFCs on climate change.

Methane is another low-hanging fruit for climate action, while we undertake the slower and more difficult transition away from CO₂-emitting energy sources.

The significant human methane emissions from leaks in reticulated gas systems, landfills, waste water treatment, and fugitive emissions from coal mining and oil and gas production can be monitored and reduced. We have the science and technology to do this now.

Both in the oil and gas sectors and in urban areas, there are many examples of how methane “hot spots” can be identified and tackled.

It’s a classic win-win that saves money and reduces climate change, and something we should be implementing in Australia in the near future.The Conversation

Zoe Loh, Research Scientist, CSIRO; Blagoj Mitrevski, Research scientist, CSIRO; David Etheridge, Principal Research Scientist, CSIRO; Nada Derek, Research Projects Officer, Oceans and Atmosphere, Climate Science Centre, CSIRO; Paul Fraser, Honorary Fellow, CSIRO; Paul Krummel, Research Group Leader, CSIRO; Paul Steele, Honorary Fellow, CSIRO; Ray Langenfelds, Scientist at CSIRO Atmospheric Research, CSIRO, and Sam Cleland, Officer in Charge, Cape Grim Baseline Air Pollution Station, Australian Bureau of Meteorology

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

Simply returning rescued wildlife back to the wild may not be in their best interest


It can be tough in the wild, especially if you’re a rescued animal or an orphan reared by human care.
Shutterstock/Andrea Geiss

Bruce Englefield, University of Sydney and Paul McGreevy, University of Sydney

There are few checks done to see how well injured or orphaned Australian animals survive after they’ve been released into the wild, we found in our new research published on Sunday.

That’s a worry for the more than 50,000 native animals that are released in Australia each year. It’s especially worrying for any orphans who’ve never experienced life in the wild.

But we found the rules governing the return of wildlife are not always in the animal’s best interest.




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Not just activists, 9 out of 10 people are concerned about animal welfare in Australian farming


Our review of Australian animal welfare legislation, regulations, codes of practice and policies found a complex regulatory system that varies between states and territories. It’s a system that is fragmented, contradictory and inconsistent.

This makes it difficult for the many thousands of volunteers and others who try to rescue and rehabilitate native animals.

Australia lags in animal welfare

We believe Australia lags behind the developed world in animal welfare and animal law. This situation evolved haphazardly and is hampered by policies that rely on assumptions based largely on neither scientific nor factual evidence.

Current policy mandates that rehabilitated rescued animals must be placed into the wild. The survival of these animals after release depends on their behavioural and physical attributes, yet some could be ill-equipped to survive.

From our reading of current regulations, any such assessment of an animal’s suitability for release is either negligible or questionable.

There is also no reliable method of identifying animals after release. Indeed, most jurisdictions forbid it and, perhaps as a direct result, there is minimal monitoring to show what happens to released animals.

Return to where?

In general, all Australian jurisdictions require rehabilitated animals to be returned to the wild. But rather than using a more general definition of rehabilitation we should think of returning the animal to its natural habitat or state.

The distinction between these two possible destinations is far from semantic. It can be argued the natural habitat (or state) of a hand-reared orphan animal, is one of captivity.

Many wildlife carers releasing an animal and seeing it disappear into the wild may equate this with success, but this may be an unfortunate convenient illusion.

The released animal may not be the happy state that carers may prefer to assume. Vague assumptions that naturalness in releasing animals to the wild is reliably associated with better well-being are largely unfounded.

But wildlife carers have no choice in the matter. They are required to consign the animals, to which they have devoted hours of care, to an uncertain fate for which they may be very poorly prepared.

And they must do so even if their knowledge, experience and pragmatism directs their thinking to more favourable alternative solutions. These include allowing some native animals to be kept in large-scale facilities such as private fenced enclosures, national parks, islands and other fenced options.

Concern for orphans in the wild

The regulations make no distinction between animals that are injured, rehabilitated and released, and those that are rescued as orphans. These are often physically unharmed but require milk substitute feeding from a bottle and nurturing by – and possible inadvertently bonding with – humans prior to release to the wild.

Adult and juvenile native animals raised in the wild usually have all their innate and learned behaviour instincts intact when they are injured and rescued.

Unless they remain in captivity for a prolonged period, or are subjected to inappropriate housing and handling, their instincts generally persist and kick-in once they have been released. They have an opportunity to survive.

In contrast, the chances for orphans to survive after release seems remote.

Orphans that needed hand-rearing generally become habituated to the smells, sounds and sights of human presence and the captive environment.

The requirement to return orphans to the wild, with no account taken of their mental state, may be difficult to defend on conservation, ethical, moral and practical grounds.

Think of the carers

The physical and mental protection of Australian injured or orphaned native wildlife should be recognised as an important animal welfare issue. The physical and mental well-being of the wildlife carers who rehabilitate them is just as important as a human welfare issue.




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Man’s stressed friend: how your mental health can affect your dog


In the absence of criteria that take into account the mental well-being of the animals and their carers, the current policy of releasing all hand-reared wildlife to the wild must be reviewed.

Using a One Welfare approach – that considers the the animals, the humans and the environment – would see a regulatory framework that balances the needs of rescued wildlife, wildlife carers and conservation.

The public and Australia’s extraordinary wildlife carers deserve to be confident that regulation is consistent among jurisdictions and reflective of best practice for the rescued wildlife and the environment.The Conversation

Bruce Englefield, PhD Student. Faculty of Veterinary Science, University of Sydney and Paul McGreevy, Professor of Animal Behaviour and Animal Welfare Science, University of Sydney

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