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Unexplained gap in global emissions of potent greenhouse gases resolved

In a new paper, published in the Proceedings of the National Academy of Sciences (PNAS), we examine the gap between the global emissions of HFCs that we infer from atmospheric observations and those reported by developed countries. The findings of the paper are summarised in a University of Bristol press release:

Until now, there has been little verification of the reported emissions of hydrofluorocarbons (HFCs), gases that are used in refrigerators and air conditioners, resulting in an unexplained gap between the amount reported, and the rise in concentrations seen in the atmosphere.  This new study shows that this gap can be almost entirely explained by emissions from developing countries. 

Currently only 42 countries are required to provide detailed annual reports of their emissions to the United Nations Framework Convention on Climate Change (UNFCCC). 

The study, led by Mark Lunt from Bristol’s School of Chemistry used HFC measurements from the international Advanced Global Atmospheric Gases Experiment (AGAGE), in combination with models of gas transport in the atmosphere, to evaluate the total emissions that are reported to the UNFCCC each year.

HFCs are potent greenhouse gases; per tonne of emissions, each gas measured in this work is hundreds or even thousands of times more effective than carbon dioxide at trapping the radiation that warms the Earth.

There is currently no global agreement to regulate the emissions of these compounds, although proposals have been made to begin phasing out their use. 

Mark Lunt said: “Any phase-out mechanism would likely be more stringent for the developed countries, but these results show that emissions from non-reporting countries are also highly significant.”

Meanwhile, the researchers note that although their estimates of total emissions from developed countries are broadly consistent with the reports that they compile, this does not necessarily mean that the emissions of each gas are being accurately reported. 

In fact, the results suggest that the most commonly used HFC is significantly over-reported whilst some other HFCs are under-reported. 

Dr Matt Rigby from the University of Bristol, who co-authored this work, said: “It appears as if the apparent accuracy of the aggregated HFC emissions from developed countries is largely due to a fortuitous cancellation of errors in the individual emissions reports.”

Professor Ron Prinn from the Massachusetts Institute of Technology (MIT), who leads the AGAGE network, added: “This study highlights the need to verify national reports of greenhouse gas emissions into the atmosphere.  Given the level of scrutiny these reports are under at the moment, it is vitally important that we improve our ability to use air measurements to check that countries are actually emitting what they claim.”

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Anaesthetic gases have a (small) influence on climate

In a paper published in Geophysical Research Letters, we quantify the influence of anaesthetic gases on global atmospheric radiative forcing. It turns out that inhalation anaesthetics are potent greenhouse gases, with 1 kg of emissions of desflurane (a commonly used anaesthetic) having the influence of around 2,500 kg of CO2. However, emissions of these gases are very low compared to CO2, so the influence on climate is still relatively small.

This paper is nicely summarised in an American Geophysical Union press release, and was picked up by the Daily Mail.

A 6-year-old girl is prepared to go under anesthesia prior to undergoing a hydrocelectomy at Forward Operating Base (FOB) Farah, Afghanistan. A new study finds that anesthesia gases are accumulating in the Earth’s atmosphere, where they make a small contribution to climate change. Credit: ISAF Headquarters Public Affairs Office/Wikimedia Commons
A 6-year-old girl is prepared to go under anesthesia prior to undergoing a hydrocelectomy at Forward Operating Base (FOB) Farah, Afghanistan. A new study finds that anesthesia gases are accumulating in the Earth’s atmosphere, where they make a small contribution to climate change.
Credit: ISAF Headquarters Public Affairs Office/Wikimedia Commons
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Little-studied man-made gases have big warming potential

We recently published a paper “Recent and Future Trends in Synthetic Greenhouse Gases” in Geophysical Research Letters describing recent trends in “synthetic” greenhouse gases (gases with no significant natural sources), and their possible impact on climate in the coming decades. The paper was summarised on the American Geophysical Union blog (thanks to Alexandra Branscombe!), and is described in the following University of Bristol press release:

Radiative forcing due to synthetic greenhouse gases. Historical values are based on AGAGE observations. Future values assume the HFC phase down schedule proposed by the US Environmental Protection Agency (2012), compared to previously published "non-policy" scenarios.
Radiative forcing due to synthetic greenhouse gases. Historical values are based on AGAGE observations. Future values assume the HFC phase down schedule proposed by the US Environmental Protection Agency (2012), compared to previously published “non-policy” scenarios.

“The total warming impact of 25 major synthetic greenhouse gases has been examined by an international team, led by researchers from the University of Bristol.

The study estimates that, without additional limits on synthetic greenhouse gas use, the resulting increase in warming could outweigh the climate benefits gained thus far from phasing down chlorofluorocarbons (CFCs).

CFCs—commonly used in refrigerators and air conditioners—garnered public attention for their role in creating a hole in the ozone layer over Antarctica.  As these chemicals were phased-down thanks to international agreements limiting their use, they were replaced by other synthesized gases that can still be harmful to the ozone layer and are greenhouse gases that contribute to climate change.  Despite this, synthetic greenhouse gases (SGHGs) beyond the CFCs have received relatively little attention from the research community—until now. 

The study, led by Dr Matthew Rigby in Bristol’s School of Chemistry, analysed observed atmospheric levels of SGHGs from 1978 to 2012, and then used these measurements to predict the impact these gases could have on global warming through 2050.

In response to the phase-down of CFCs through the 1987 Montreal Protocol, the researchers discovered that the use of other synthetic gases as refrigerants—such as hydrofluorocarbons (HFCs)—has risen.  HFCs had been limited in the now-defunct 1997 Kyoto Protocol, but there is currently no agreement restricting their use.  So, using HFCs as a test case, the researchers examined the effect of phasing down HFCs by amending the Montreal Protocol to include these gases.

Dr Rigby said: “We could avoid adding the equivalent of up to another three years of carbon dioxide emissions into the atmosphere if these gases were being phased down.”

HFCs are particularly strong greenhouse gases, so even relatively small levels in the atmosphere can contribute to warming.

“Per tonne of emissions, HFCs are much more potent greenhouse gases than carbon dioxide, and are very good at trapping the radiation that heats the Earth,” Dr Rigby said.

While HFCs are currently not a major driver of climate change compared to carbon dioxide or even other SGHGs, the researchers point out that if unabated they may contribute significantly to future warming.

The study used measurements of SGHG levels from the Advanced Global Atmospheric Gases Experiment (AGAGE), a global observing system developed by Professor Ronald Prinn of the Massachusetts Institute of Technology (MIT) and colleagues, and sponsored by NASA and other agencies.

Professor Prinn, co-director of the MIT Joint Program on the Science and Policy of Global Change and a co-author of the report said: “Addressing HFCs, and other SGHGs, now will ensure that they don’t contribute significantly to warming in the future.”

Meanwhile, the researchers note that due to extensive use, CFCs will continue to warm the planet for years to come.

“CFCs have contributed the most among the synthetic greenhouse gases to warming.  Their use peaked and levels are now declining, but these gases will remain in the atmosphere for many years.  This is likely the trend we will see with most SGHG gases, so it is important that we address these gases now before they do more severe damage,” said Professor Prinn.”

(With particular thanks to Audrey Resutek who wrote the MIT press release that this is based on).

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35 years of AGAGE measurements

I’ve just returned from the 35th anniversary AGAGE meeting in Boston, MA. I’ve written a blog post for the Cabot Institute, summarising the changes AGAGE has seen during this time:

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

“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.

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.

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.

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 well 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!”

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GAUGE kicks off!

GAUGE schematic

On the 1st March, we officially began our new £3m NERC-funded consortium project Greenhouse gAs Uk and Global Emissions (GAUGE). The University of Bristol press release explains:

Scientists awarded grant to determine UK’s greenhouse gas emissions
Press release issued 1 March 2013

Researchers in the University of Bristol’s Atmospheric Chemistry Research Group (ACRG), in collaboration with scientists around the country, have been awarded funding from the Natural Environment Research Council (NERC) to provide an independent ‘top-down’ check on the UK’s greenhouse gas emissions estimates.

GAUGE schematic
GAUGE will involve measurements of greenhouse gases from the air, sea and space in an effort to better quantify UK emissions

The UK is required to estimate how much climate-warming carbon dioxide, methane and nitrous oxide it emits each year. However, at the moment, these estimates rely heavily on so-called ‘bottom-up’ accounting methods that may be subject to biases and inaccuracies.

The GAUGE project (Greenhouse gAs Uk and Global Emissions) is a three and a half year collaboration between several universities and research institutions across the UK.

ACRG’s Professor Simon O’Doherty, who also runs the UK greenhouse gas monitoring network funded by the Department for Energy and Climate Change, said: “It’s important that we expand our greenhouse gas observation capabilities in this country, if we’re really going to understand what we’re emitting. But it’s equally important that we begin exploring new types of measurement, which may help us understand emissions processes more fundamentally.”

GAUGE will bring together a more comprehensive suite of greenhouse gas observations around the UK than has ever been compiled. The project will determine emissions using information from satellites, aircraft, tall towers (including the BT tower in the middle of London), balloons and boats.

In addition to developing new measurements, GAUGE will use computer models to simulate how greenhouse gases travel through the air.

Dr Matt Rigby, a research fellow at ACRG, said: “By measuring the concentration of greenhouse gases in the atmosphere, and then using computer models to simulate where the air came from in the days before the measurements, we can determine emissions from the surrounding areas. This new funding will allow us to develop these methods with the help of the Met Office and GAUGE partners at other universities.”

Using the new measurements and modelling techniques, GAUGE researchers hope to make the UK’s emissions amongst the best-quantified in the world.

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Visit to Westminster

On the 29th October, I visited Westminster, where I was shadowing Stephen Williams MP as part of the Royal Society Pairing Scheme. The week was a great opportunity to find out how policy makers get access to scientific research.

The University ran a press release about the event, saying:

Dr Matt Rigby from the University of Bristol will be swapping a lab coat for legislation, when he visits MP Stephen Williams at the House of Commons for a “Week in Westminster” commencing Monday 29 October as part of a unique ‘pairing’ scheme run by the Royal Society – the UK’s national academy of science.

During his visit Dr Rigby will shadow his MP pair and learn about his work, as well as attending a House of Commons Science and Technology Committee meeting and Prime Minister’s Question Time and meeting Professor Sir John Beddington, Government Chief Scientific Advisor. The visit will provide him with a behind-the-scenes insight into how science policy is formed as well as an understanding of the working life of an MP.

Dr Rigby said: “This will be a great opportunity to learn first-hand how science is translated into public policy. We’re often told that we need to get out of the lab and engage with policy-makers, and I think this will be fantastic way to see how we can interact more effectively.”

The Royal Society’s MP-Scientist pairing scheme aims to build bridges between parliamentarians and some of the best scientists in the UK. It is an opportunity for MPs to become better informed about science issues and for scientists to understand how they can influence science policy. Over 200 pairs of scientists and MPs have taken part in the scheme since it was launched in 2001.

Sir Paul Nurse, President of the Royal Society said: “We live in a world facing increasing challenges that can only be addressed with a clear understanding of science. From climate change to influenza outbreaks, GM food to nuclear power, our MPs have to make decisions about complex issues that will affect the lives of all those in the UK and, in many cases, more widely throughout the world. This means that MPs and scientists have a responsibility to engage with each other to get the best possible scientific advice into public policy making.

“We set up the Royal Society’s MP Scientist pairing scheme in 2001 to provide the opportunity for MPs and scientists to build long-term relationships with each other and have now organised over two hundred pairings.

“I know many parliamentarians and scientists who have gained from the scheme, and the shaping of public policy can only improve over time as these relationships continue to grow.”