AGAGE – Cabot Institute for the Environment blog

Monitoring greenhouse gas emissions: Now more important than ever?

Posted on October 15, 2018April 13, 2023 by janet.crompton

As part of Green Great Britain Week, supported by BEIS, we are posting a series of blogs throughout the week highlighting what work is going on at the University of Bristol’s Cabot Institute for the Environment to help provide up to date climate science, technology and solutions for government and industry. We will also be highlighting some of the big sustainability actions happening across the University and local community in order to do our part to mitigate the negative effects of global warming. Today our blog will look at ‘Explaining the latest science on climate change’.

The IPCC report

On 8 October 2018 the Intergovernmental Panel on Climate Change (IPCC) [1] published their special report on Global Warming of 1.5 ˚C. As little as 24 hours after the report had been published, the results of the report were already receiving extensive global coverage in the media, with BBC News describing the report as the “final call”. The BBC News article also explicitly mentions that this is “the most extensive warning yet on the risks of rising global temperatures. Their dramatic report on keeping that rise under 1.5 ˚C states that the world is now completely off track, heading instead towards 3 ˚C. Staying below 1.5 ˚C will require ‘rapid, far-reaching and unprecedented changes in all aspects of society’ [2].”

Reading the report has quite honestly been somewhat overwhelming but also necessary to understand exactly what we are in for. And as much as I understand the difficulty one might face either with the technical terms of the report or even the volume of information, I would really encourage you to give it a read. This special report covers a wide range of subjects from oceans, ice and flooding to crops, health and economy. However, if you do find that the chapters themselves are too lengthy or difficult, there is an amazing interactive, and very easy way that will help you explore the impacts of a 1.5 ˚C, 2 ˚C and beyond on Carbon Brief’s website.

There are two distinct parts in the IPCC special report. The full technical report that consists of 5 chapters and a short summary for policy makers (SPM). The SPM clearly states that “Estimated anthropogenic global warming matches the level of observed warming to within ±20 %” which translates into ‘almost 100 % of the warming is the result of human activity’ [3] [4].

We know for a fact that human activity is warming the planet

One outcome of this “human activity” that we often discuss is the emission of greenhouse gases (GHGs). Through various types of activities, whether that is agriculture, deforestation or burning fossil fuels, GHGs are emitted to the atmosphere. Without going too much into the chemistry and physics, what these GHGs do is change the mixing ratios within the atmosphere, resulting in greater absorbance of infrared radiation. And it is this change in the composition of our atmosphere that we refer to as the manmade greenhouse gas effect which also leads to the warming described in the IPCC report. But far more than the warming effect itself, global warming has all sorts of impacts most of which you can explore through the interactive link above.

Greenhouse gases and a long history of monitoring

Some of the ‘usual suspects’ in the discussion of GHG emissions are carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) (often described as the ‘major’ greenhouse gases [5]). However, an often-overlooked set of halogenated greenhouse gases are playing an increasingly large role in anthropogenic driven climate change. Gases like perfluorocarbons (PFCs) and hydrofluorocarbons (HFCs) are compounds that are emitted through some form of human activity. In the case of PFCs for example, the GHGs CF4 and C2F6 are two of the most volatile and long-lived gases monitored under the Kyoto protocol [6] and they are both primarily emitted through or during industrial processes. In contrast, HFCs are used widely as coolants in refrigerators and air-conditioning units, as blowing agents in foam manufacture and propellants in aerosols. They were originally introduced to replace ozone-depleting gases such as chlorofluorocarbons (CFCs), but like their predecessors, are potent greenhouse gases. Given the long lifetime of many of these halogenated gases, current emissions will influence the climate system for decades to come.

In order to monitor the accumulation of these gases in atmosphere, high-precision measurements are required. Through projects such as the Advanced Global Atmospheric Gases Experiment (AGAGE) [7] (figure 1 [8]) that has been measuring the composition of the global atmosphere continuously since 1978 and the National Oceanic and Atmospheric Administration’s Earth System Research Laboratory Global Monitoring Division, scientists have tracked the atmospheric concentrations of climate forcing gases from as far back as 1950s [9].

Figure 1: The AGAGE network

The Atmospheric Chemistry Research Group (ACRG) Chemistry Department, University of Bristol

The ACRG carries out research in the UK and worldwide in collaboration with other atmospheric chemistry research centres, universities and third parties. In the UK, the ACRG runs the UK Deriving Emissions linked to Climate Change network (DECC) [10], funded by the Department for Business, Energy and Industrial Strategy (BEIS) to measure atmospheric GHG and ozone depleting substances over the UK. These measurements are used in elaborate mathematical models to create top-down emission estimates for the UK and verify the UK GHG inventories submitted to the United Nations Framework Convention for Climate Change (UNFCCC) as part of the Kyoto protocol. Worldwide, the group is involved in the AGAGE network, monitoring global background levels of a wide range of GHGs. The ACRG runs 2 of the 9 global background stations under the AGAGE programme. One of these is the Mace Head station (Figure 2) on the west coast of Ireland, which is ideally placed for resolving northern hemispheric baseline air amongst European pollution events. The other AGAGE research station managed by the ACRG is the site at Ragged Point, Barbados. This site just north of the tropics, sits on the eastern edge of the island of Barbados and is directly exposed to the Atlantic. The researchers in ACRG study a variety of GHGs and a very large range of topics from maintaining instrument suites to ensuring the quality of the resulting data so that it can be used in modelling studies.

Figure 2: The Mace Head Station (Credit: Dr Kieran Stanley)

Why are measuring stations and networks like AGAGE so valuable and more important than ever?

The answer to this question is straightforward. Without measurement stations and their underlying networks, we would have very few means [11] by which to measure the accumulation of GHGs in the global atmosphere, and consequently no way of evaluating their emissions without relying on statistics from the industries that emit them. The current IPCC report is underpinned by such measurements, which allow scientists to estimate the impact of anthropogenic activity on past, present and future climates.

From Mauna Loa and its 60 -year record of atmospheric CO2 [12], to unexpected growth in emissions of banned substances such as CFC – 11 [13] and monitoring the accumulation of extremely long-lived greenhouse gases in the global atmosphere, atmospheric measurements stations have been our inside man when it comes to keeping track of what is happening in our atmosphere and to what extent human activities are altering its composition.

Perhaps now more than ever, in the light of the IPCC report, we can appreciate the importance of the data that have been collected over decades but also, the efforts of those who have been directly or indirectly involved in this kind of work. Continuing and expanding the measurement networks for these gases is and will be even more vital for a continued understanding of global and regional GHG emission trends.

References

[1] http://www.ipcc.ch/
[2] https://www.bbc.co.uk/news/science-environment-45775309
[3] http://report.ipcc.ch/sr15/pdf/sr15_spm_final.pdf
[4] https://www.carbonbrief.org/analysis-why-scientists-think-100-of-global-warming-is-due-to-humans
[5] https://www.c2es.org/content/main-greenhouse-gases/
[6] https://www.atmos-chem-phys.net/10/5145/2010/acp-10-5145-2010.pdf
[7] https://agage.mit.edu/
[8] https://agage.mit.edu/
[9] https://www.esrl.noaa.gov/gmd/about/aboutgmd.html
[10] http://www.bristol.ac.uk/chemistry/research/acrg/current/decc.html
[11] https://www.co2.earth/co2-ice-core-data
[12] https://www.co2.earth/daily-co2
[13] https://www.theguardian.com/environment/2018/may/16/mysterious-rise-in-banned-ozone-destroying-chemical-shocks-scientists

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This blog is written by Cabot Institute members Eleni Michalopoulou, Dr Dan Say, Dr Kieran Stanley and Professor Simon O’Doherty from the University of Bristol’s School of Chemistry.

Dan Say

Eleni Michalopoulou

Read other blogs in this Green Great Britain Week series:
1. Just the tip of the iceberg: Climate research at the Bristol Glaciology Centre
2. Monitoring greenhouse gas emissions: Now more important than ever?
3. Digital future of renewable energy
4. The new carbon economy – transforming waste into a resource
5. Systems thinking: 5 ways to be a more sustainable university
6. Local students + local communities = action on the local environment

‘New’ man-made gases: Ozone crisis or hoax?

Posted on March 14, 2014April 19, 2023 by janet.crompton

Image by PiccoloNamek (English wikipedia)
[GFDL (www.gnu.org/copyleft/fdl.html),
via Wikimedia Commons

You may have noticed a story reported on widely recently on the discovery of 4 ‘new’ man-made ozone-depleting gases. This follows the publication of a study in the journal Nature Geoscience on the first measurements of these gases, their abundances in the atmosphere and estimated global emission rates. Responses to the reporting of this publication have ranged from the Daily Mail’s “Ozone Crisis” to the inevitable internet-based diatribe of “any research from UEA is clearly made up” in various comment sections. So just how concerned should we be about the emissions of these four gases?

Chlorofluorcarbons (CFCs)

The reason we care about CFCs is because they deplete ozone high up in the atmosphere, potentially exposing humans to harmful UV rays. Oh, they also happen to be extremely potent greenhouse gases, with each molecule of a CFC being equivalent to 1000s of molecules of CO₂, and they sit around in the atmosphere for 10s or 100s of years before being removed. Basically they’re pretty bad, and sure they might have been great refrigerants and aerosol propellants but at what cost?

The production of CFCs has now to all intents and purposes ceased, although that doesn’t mean that emissions have completely stopped; various banks of these gases exist in fridges for example. These might leak during use or when destroyed. So it’s not entirely surprising to read that this study has found that various CFCs are still being released.

Newly measured

In fact the reason this paper is important is more to do with the fact that these gases have never before been measured. Many of the media articles seem to lead with the fact these are ‘new’ ozone-depleting gases, which is a little misleading. They’re not new; they’ve been around for decades, only nobody has been able to measure them in the atmosphere before. Why’s that you might ask? Well much of it is to do with just how small their concentrations are in the atmosphere.

The fact of the matter is that the concentrations of these gases (CFC-112, CFC-112a, CFC-113a, HCFC-133a) are tiny. All four have atmospheric mixing ratios of less than 1 part per trillion (ppt). In other words, if you could isolate a trillion molecules of air (1 x 10¹²) then not even one of them would be one of these ’new’ CFCs. By contrast CO₂ in the atmosphere has a mixing ratio of hundreds of parts per million.

Compare these newly measured gases to the major CFCs (CFC-11, CFC-12, CFC-113) whose current atmospheric concentrations are hundreds if not thousands of times greater. Even though emissions of these major CFCs are now close to zero they will still be around in the atmosphere at these elevated concentrations for decades to come. This is shown in the plot below taken from the AGAGE network measurements of CFC-12. Although the concentration has reached a peak it will take at least one hundred years for levels to get back down to pre-1980 levels, with the current mixing ratio still over 500 ppt.

Plot taken from the AGAGE network measurements of CFC-12

So emissions of these newly measured gases would have to really pick up for a sustained period of time to add significantly to the ozone-depleting effect of what is already in the atmosphere. To say the measurement of these compounds has created some sort of ozone crisis is therefore a gross exaggeration. That’s not to say that this work was a waste of time; it’s vital that we know about these compounds and their atmospheric abundance so we can ensure their contribution to ozone depletion remains negligible.

Other factors influencing ozone recovery

There are other potentially more important causes for concern as well. Hydrochlorofluorocarbons (HCFCs) were introduced as replacements for CFCs but also contribute to ozone depletion, albeit in a less effective way. Although these are also being phased out many of these will have a greater impact on the recovery of the ozone ‘hole’ than these newly measured species. Just a few months ago the United Nations Environment Programme (UNEP) released a report saying another gas, Nitrous Oxide (N₂O), is now considered to be the biggest threat to the ozone layer over the next 50 years. Not to mention that one of the impacts of a rise in global surface temperatures could be a slowing in ozone hole recovery. There’s a genuinely interesting (honest!) explanation for why that is which I will cover in another blog.

The point is that there are lots of factors which affect the Earth’s ozone layer. Studies like the one recently published in Nature Geoscience are vital for our understanding of what the recent and current atmospheric composition is like. It might not be a problem now, but surely the key to looking after our planet, and ourselves, is to prevent things from becoming problematic in future. If we can take steps to find out where these emissions are coming from and why some of them are increasing then measures could be put in place to limit their future influence on ozone recovery.

This blog is written by Mark Lunt, Atmospheric Chemistry Reseach Group, Cabot Institute, University of Bristol, .

Mark Lunt

35 years monitoring the changing composition of our atmosphere

Posted on November 4, 2013April 20, 2023 by janet.crompton

I work on an experiment that began when the Bee Gees’ Stayin’ Alive was at the top of the charts. The project is called AGAGE, the Advanced Global Atmospheric Gases Experiment, and I’m here in Boston, Massachusetts celebrating its 35-year anniversary. AGAGE began life in 1978 as the Atmospheric Lifetimes Experiment, ALE, and has been making high-frequency, high-precision measurements of atmospheric trace gases ever since.

At the time of its inception, the world had suddenly become aware of the potential dangers associated with CFCs (chlorofluorocarbons). What were previously thought to be harmless refrigerants and aerosol propellants were found to have a damaging influence on stratospheric ozone, which protects us from harmful ultraviolet radiation. The discovery of this ozone-depletion process was made by Mario Molina and F. Sherwood Rowland, for which they, and Paul Crutzen, won the Nobel Prize in Chemistry in 1995. However, Molina and Rowland were not sure how long CFCs would persist in the atmosphere, and so ALE, under the leadership of Prof. Ron Prinn (MIT) and collaborators around the world, was devised to test whether we’d be burdened with CFCs in our atmosphere for years, decades or centuries.

Fig 1. The AGAGE network

ALE monitored the concentration of CFCs, and other ozone depleting substances, at five sites chosen for their relatively “unpolluted” air (including the west coast of Ireland station which is now run by Prof. Simon O’Doherty here at the University of Bristol). The idea was that if we could measure the increasing concentration of these gases in the air, then, when combined with estimates of the global emission rate, we would be able to determine how rapidly natural processes in the atmosphere were removing them.

Fig 2. Mace Head station on the West coast of Ireland

Thanks in part to these measurements, we now know that CFCs will only be removed from the atmosphere over tens to hundreds of years, meaning that the recovery of stratospheric ozone and the famous ozone “hole” will take several generations. However, over the years, ALE, and now AGAGE, have identified a more positive story relating to atmospheric CFCs: the effectiveness of international agreements to limit gas emissions.

The Montreal Protocol on Substances that Deplete the Ozone Layer was agreed upon after the problems associated with CFCs were recognised. It was agreed that CFC use would be phased-out in developed countries first, and developing countries after a delay of a few years. The effects were seen very rapidly. For some of the shorter-lived compounds, such as methyl chloroform (shown in the figure), AGAGE measurements show that global concentrations began to drop within 5 years of the 1987 ratification of the Protocol.

Figure 3. Concentrations of methyl chloroform, a substance banned under the Montreal Protocol, measured at four AGAGE stations.

Over time, the focus of AGAGE has shifted. As the most severe consequences of stratospheric ozone depletion look like they’ve been avoided, we’re now more acutely aware of the impact of “greenhouse” gases on the Earth’s climate. In response, AGAGE has developed new techniques that can measure over 40 compounds that are warming the surface of the planet. These measurements are showing some remarkable things, such as the rapid growth of HFCs, which are replacements for CFCs that have an unfortunate global-warming side effect, or the strange fluctuations in atmospheric methane concentrations, which looked like they’d plateaued in 1999, but are now growing rapidly again.

The meeting of AGAGE team members this year has been a reminder of how important this type of meticulous long-term monitoring is. It’s also a great example of international scientific collaboration, with representatives attending from the USA, UK, South Korea, Australia, Switzerland, Norway and Italy. Without the remarkable record that these scientists have compiled, we’d be much less informed about the changing composition of the atmosphere, more unsure about the lifetimes of CFCs and other ozone depleting substances, and unclear as to the exact concentrations and emissions rates of some potent greenhouse gases. I’m looking forward to the insights we’ll gain from the next 35 years of AGAGE measurements!This blog was written by Dr Matt Rigby, Atmospheric Chemistry Research Group, University of Bristol.

Matt Rigby