Global stocktake shows the 43 greenhouse gases driving global warming

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A wide range of industrial processes have released greenhouse gases into the atmosphere.
Paulo Resende/

Pep Canadell, CSIRO; Cathy Trudinger, CSIRO; David Etheridge, CSIRO; Malte Meinshausen, University of Melbourne; Paul Fraser, CSIRO, and Paul Krummel, CSIRO

The most comprehensive collection of atmospheric greenhouse gas measurements, published today, confirms the relentless rise in some of the most important greenhouse gases.

The data show that today’s aggregate warming effect of carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) is higher than at any time over the past 800,000 years, according to ice core records.

Building on half a century of atmospheric measurements by the international research community, we compiled and analysed the data as part of a group of international scientists, led by Malte Meinshausen from the University of Melbourne in collaboration with CSIRO.

Together, the data provide the most compelling evidence of the unprecedented perturbation of Earth’s atmosphere. They clearly show that the growth of greenhouse gases began with the onset of the industrial era around 1750, took a sharp turn upwards in the 1950s, and still continues today.

Research has demonstrated that this observed growth in greenhouse gases is caused by human activities, leading to warming of the climate – and in fact more than the observed warming, because part of the effect is currently masked by atmospheric pollution (aerosols).

The new collection of records comes from measurements of current and archived air samples, air trapped in bubbles in ice cores, and firn (compacted snow). The data cover the past 2,000 years without gaps, and are the result of a compilation of measurements analysed by dozens of laboratories around the world, including CSIRO, the Bureau of Meteorology’s Cape Grim Station, NOAA, AGAGE and the Scripps Institution of Oceanography, among others.

These data include 43 different greenhouse gases released into the atmosphere from dozens of human activities and industrial processes. While CO₂, CH₄ and N₂O are on the rise, some other greenhouse gases such as dichlorodifluoromethane (CFC-12) are slowly starting to decline as a result of policies to ban their use.

Author provided

The greenhouse gases

Most of us know that CO₂, CH₄ and N₂O are among the principal causes of human-induced climate change. They are found in the atmosphere in the absence of human activity, but the increases in their concentrations are due to human activities such as burning fossil fuels, deforestation and agriculture (livestock, rice paddies, and the use of nitrogen-based fertilisers). They are all from biological or fossil fuel sources.

But there is much more when it comes to greenhouse gases. Our analysis features a further 40 greenhouse gases (among hundreds that exist), many of them emitted in very small quantities. Although many might play a small role, dichlorodifluoromethane (CFC-12) and trichlorofluoromethane (CFC-11) are the third and fifth most important greenhouse gases respectively, in terms of their overall contributions to global warming.

Most of these gases are emitted exclusively by humans, the so-called synthetic greenhouse gases, and have been used variously as aerosol spray propellants, refrigerants, fire-extinguishing agents, and in the production of semiconductors, among other industrial applications.

Synthetic greenhouse gases include chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), most perfluorocarbons (PFCs), sulfur hexafluoride (SF₆), and others. Several, most famously CFCs, also deplete the ozone layer and are regulated under the Montreal Protocol. Others, such as HFCs, were actually first produced in large quantities to replace the ozone-depleting substances, but unfortunately turned out to be potent greenhouse gases too.

Importantly, all 43 greenhouse gases offer opportunities to tackle climate change, either by reducing their emissions or, in the case of synthetic gases, finding non-greenhouse alternatives.

Not all greenhouse gases are the same

How much a greenhouse gas contributes to warming depends on three factors. The first is how much gas is emitted. Second is how much a kilogram of that gas will warm the planet once it’s in the atmosphere. And third is how long the gas will remain in the atmosphere.

CO₂ is the most important greenhouse gas in warming the planet, despite being the weakest greenhouse gas per unit of mass. Its contribution to warming comes from the sheer scale of emissions (40 billion tonnes emitted each year), and the fact that a large part effectively hangs around in the atmosphere for hundreds or thousands of years after emission. The resulting concentration makes CO₂ responsible for about 65% of all warming due to greenhouse gas emissions from human activities.

This makes CO₂ the most important factor in determining future global warming. Unless we can cut CO₂ emissions to zero by the second half of this century, primarily by finding alternatives to fossil fuels, the world will continue to warm beyond the 2℃ target of the Paris Agreement, not to mention the aspirational 1.5℃ goal.

Provided by University of Melbourne

Methane (CH₄) is the next most important greenhouse gas, with current concentration contributing about 15% of overall human-induced warming.

Most synthetic greenhouse gases have very high global warming potentials. The one with the highest current emissions is the refrigerant HFC-134a, which is 1,300 times more potent than CO₂ (per mass unit emitted). Other synthetic greenhouse gases have even more extraordinary warming potentials, with CF₄ (used in the semiconductor industry) and SF₆ (from industrial electricity transformers) being 6,500 and 23,400 times more potent than CO₂, respectively.

CFC-12, a former refrigerant, is both a potent ozone-depleting substance and a powerful greenhouse gas. Although its emissions and atmospheric concentrations are now declining thanks to global compliance with the Montreal Protocol, it is still the third most important greenhouse gas and responsible for 6-7% of all warming since the beginning of the industrial era.

What are these GHG data good for?

Our new compilation of greenhouse gas data is the most complete and robust picture to date showing the main drivers of climate change, and how we humans are altering the Earth’s atmosphere. Global temperature is now about 1℃ warmer on average than pre-industrial temperatures.

The new database also serves as an accurate measure of greenhouse gas concentrations resulting from past human and natural emissions, which will in turn help to improve the performance of climate models. Building trust and confidence in climate projections starts by testing and running models with real data during historical periods. The new climate projections will feed in the next major report from the Intergovernmental Panel on Climate Change, due to be released in 2021.

The ConversationContinued greenhouse gas monitoring, including significant contributions by Australia, is crucial to understand how the planet reacts to human interference, and to better plan for adaptation to a changing climate. Global and regional greenhouse data can help nations to track the long-term global targets under the Paris agreement, and to inform actions needed to stabilise the climate.

Pep Canadell, CSIRO Scientist, and Executive Director of the Global Carbon Project, CSIRO; Cathy Trudinger, Senior Research Scientist, CSIRO; David Etheridge, Principal Research Scientist, CSIRO; Malte Meinshausen, A/Prof., School of Earth Sciences, University of Melbourne; Paul Fraser, Honorary Fellow, CSIRO, and Paul Krummel, Research Group Leader, CSIRO

This article was originally published on The Conversation. Read the original article.

Around the world, environmental laws are under attack in all sorts of ways

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In Montana and Idaho, endangered gray wolves are no longer safe outside national parks.
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Bill Laurance, James Cook University

As President Donald Trump mulls over whether to pull out of the Paris climate agreement, it is hard to imagine that he’s listening to the experts. US climate researchers are being so stifled, ignored or blackballed that France has now offered sanctuary to these misunderstood souls.

One might prefer to think of Trump as an outlier in an otherwise environmentally sane world. But alarmingly, there’s just too much evidence to the contrary.

A recent analysis, led by Guillaume Chapron of Sweden’s Agricultural University, reveals a rising tide of assaults on environmental safeguards worldwide. If nothing else, it illustrates the sheer range and creativity of tactics used by those who seek to profit at the expense of nature.

The assaults on environmental protections are so diverse that Chapron and his colleagues had to devise a new “taxonomy” to categorise them all. They have even set up a public database to track these efforts, giving us a laundry list of environmental rollbacks from around the world.

Nick Kim /

One might perhaps hope that species staring extinction in the face would be afforded special protection. Not in the western US states of Idaho and Montana, where endangered gray wolves have been taken off the endangered species list, meaning they can be shot if they stray outside designated wilderness or management areas.

In Western Australia, an endangered species can be legally driven to extinction if the state’s environment minister orders it and parliament approves.

Think diverse ecosystems are important? In Canada, not so much. There, native fish species with no economic, recreational or indigenous value don’t get any legal protection from harm.

And in France – a crucial flyway for Eurasian and African birds – killing migratory birds is technically illegal. But migrating birds could be shot out of the sky anyway because the environment minister ordered a delay in the law’s enforcement.

In South Africa, the environment minister formerly had authority to limit environmental damage and oversee ecological restoration at the nation’s many mining sites. But that power has now been handed over to the mining minister, raising fears of conflict between industry and environmental interests.

In Brazil, the famous Forest Code that has helped to reduce deforestation rates in the Amazon has been seriously watered down. Safeguards for forests along waterways and on hillsides have been weakened, and landowners who illegally fell forests no longer need to replant them.

In the Indian Ocean island nation of Mauritius, endangered species are protected by law, unless it is deemed to be in the “national interest” not to do so. Although an endangered species, the endemic Mauritius flying fox was annoying commercial fruit farmers, so the government has allowed more than 40,000 flying foxes to be culled.

And in Indonesia, it’s illegal to carry out destructive open-pit mining in protected forest areas. But aggressive mining firms are forcing the government to let them break the law anyway, or else face spending public money on legal battles.

Shoot the messengers

Campaigners should also beware. Under new legislation proposed in the UK, conservation groups that lose lawsuits will be hit with heavy financial penalties.

In many parts of the world, those who criticise environmentally destructive corporations are getting hit with so-called “strategic lawsuits against public participation”, or SLAPP suits.

In Peru, for instance, a corporation that was mowing down native rainforest to grow “sustainable” cacao for chocolate routinely used lawsuits and legal threats to intimidate critics.

That’s before we’ve even discussed climate change, which you might not be allowed to do in the US anyway. Proposed legislation would prohibit the government from considering climate change as a threat to any species. No wonder researchers want to move overseas.

Nick Kim /

As the above examples show, essential environmental safeguards are being conveniently downsized, diminished, ignored or swept under the carpet all over the world.

Viewed in isolation, each of these actions might be rationalised or defended – a small compromise made in the name of progress, jobs or the economy. But in a natural world threatened with “death by a thousand cuts”, no single wound can be judged in isolation.

Without our hard-won environmental protections, we would all already be breathing polluted air, drinking befouled water, and living in a world with much less wildlife.

The ConversationThis article is an edited version of a blog post that originally appeared here.

Bill Laurance, Distinguished Research Professor and Australian Laureate, James Cook University

This article was originally published on The Conversation. Read the original article.