Dan Say’s work on our re-evaluation of the UK’s HFC emissions featured on the University of Bristol News. Based on an analysis of atmospheric data, we found that the UK’s estimates of the emissions of HFC-134a, used in car air conditioning, were likely too high. Dan took a closer look at the UK inventory and found that estimates of the frequency at which car air conditioning units were refilled, and the number of cars with air conditioning units in them were likely over-estimated in the inventory.
The government is now re-evaluating the assumptions that go in to their HFC-134a calculations.
“The amount of greenhouse gases that the UK produces is calculated annually by the Department for Energy and Climate Change (DECC). Researchers at the University of Bristol independently verify these estimates using atmospheric measurements, making the UK one of only three countries in the world that does so.
“Our work is used by the DECC for monitoring compliance with international and domestic legislation; identifying priorities for improving inventory accuracy; assessing the UK’s progress towards targets set in the Montreal and Kyoto Protocols; evaluating the impact of policy; and informing international negotiations.” – Professor Simon O’Doherty
The UK is signed up to the Montreal Protocol (which aims to reduce the amount of ozone depleting compounds emitted) and the Kyoto Protocol (which aims to reduce the amount of anthropogenic greenhouse gases in the atmosphere). These require the UK to report its emissions on a regular basis, but it’s not as straightforward as simply measuring the gases in the atmosphere.
Reporting the amount of man-made greenhouse gases that the UK produces annually is a challenging task. Like the other 191 countries that have signed up to the Kyoto protocol, the UK uses an inventory approach to estimate the emissions, as directly measuring anthropogenic greenhouse gases is too complicated. This involves estimating emissions from a variety of activities such as burning fossil fuels, agriculture and energy production. But the UK is one of only three countries that go one-step further, by using atmospheric measurements to validate these inventory calculations.
This independent verification is performed by researchers from the University of Bristol’s Atmospheric Chemistry Research Group which is part of the Cabot Institute and the School of Chemistry. Using a combination of physical measurement and sophisticated modelling techniques, Professor Simon O’Doherty and Dr Matt Rigby work in collaboration with Dr Alistair Manning from the UK Met Office to monitor the greenhouse gases in the atmosphere above the UK.
In order to do this, the researchers developed the UK DECC Network – a unique national greenhouse gas monitoring system comprising six stations making high-frequency measurements of key atmospheric trace gases. Analysis and interpretation of these observations using state-of-the-art modelling techniques enables the independent assessment of the UK’s adherence to the Montreal and Kyoto Protocols.
“Our work started more than 20 years ago when we provided data to the Government on the accumulation of ozone-depleting gases in the atmosphere resulting in the signing of the Montreal Protocol,” says O’Doherty. “We have been able to show how the use of chlorofluorocarbons (CFCs) has risen and fallen over the years and that direct measurement of atmospheric gases can be used to monitor the impact of legislation such as the Montreal Protocol.”
Back then O’Doherty only had one monitoring station at his disposal, but today he can use data from a network of stations across the country as well as aircraft, satellites and even ferries that measure climatically important gases such as carbon dioxide, methane and nitrous oxide. When combined with models of atmospheric gas transport, these observations provide an independent means of assessing natural and man-made emissions. As well as monitoring the UK’s compliance with international treaties, these data have been central to recent World Meteorological Office (WMO) Scientific Assessments of Ozone Depletion produced between 2007 and 2010 and to the Nobel Prize-winning Inter Governmental Panel on Climate Change (IPCC) Assessment of Climate Change published in 2007.
The data will also form the basis for negotiations of future targets for UK emissions.
“Future climate treaties will take recent emissions estimates as a baseline from which to plan emissions reductions. Therefore, it’s really important that we are able to get these estimates right, both in the UK and around the world, so that the burden for emissions reductions is shared in a fair way,” says Dr Rigby.
One of the biggest challenges for the future is distinguishing between natural and man-made greenhouse gases. O’Doherty and Rigby are now investigating new techniques that could measure different isotopic compounds and thus distinguish between anthropogenic and naturally emitted greenhouse gases.
Key facts: • The underpinning research was funded by the Department for Energy and Climate Change, the Natural Environment Research Council and NASA. • Man-made greenhouse gas emissions cannot currently be measured directly but instead are calculated by estimating emission from a number of activities such as the burning of fossil fuels. • Bristol researchers independently verify these calculations by taking atmospheric measurements and using atmospheric models to calculate the source of the emissions. • The UK now has a network of stations, managed by Professor Simon O’Doherty, that continuously monitor important atmospheric gases. • The data from the monitoring stations is used to verify if the UK is adhering to the Montreal and Kyoto protocols, as well as to inform international policy on climate change. • The UK is one of only three countries in the world that collects data and verifies emissions in this way.”
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.
I was recently interviewed for a report on the environmental impacts of refrigerant gases on behalf of a company that makes hydrocarbon refrigerant blends. The report is called “Hydrocarbons: The Quest For A Green Solution To The Changing Future Of Refrigeration And Air-Conditioning” is available on the PriorityCool Refrigerants website.
Artist Neville Gabie has put together a striking piece of work called “Collective Breath“, which culminated in this video, filmed at Mace Head research station in Ireland. The piece is an instrument that is played using the compressed breath of 1111 people from the WOMAD festival. Neville, who I met through a Cabot Institute event, was partly inspired by some of the equipment that we used for compressing and storing air samples in the Atmospheric Chemistry Research Group. I gave a short talk on greenhouse gases at the installation at WOMAD.
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.”
Although methane is the second most important greenhouse gas its sources are quite poorly understood. However, new methods of measuring atmospheric methane may be able to help.
Methane is a molecule containing one carbon and four hydrogen atoms. These atoms usually have an atomic mass unit of 12 (carbon) and 1 (hydrogen). However, they also occur in higher masses in nature, called isotopes. Carbon-13 and deuterium (hydrogen with a mass of 2) occur in one atom for every few thousand atoms of regular carbon or hydrogen. This becomes potentially useful for us, because different sources of methane emit molecules with slightly different ratios of carbon-12 to carbon-13 or different ratios of hydrogen to deuterium. For example, methane emitted from wetlands has less 13C than the average in the atmosphere, whereas wildfires emit methane with a relatively high deuterium content.
So, by measuring methane concentrations and isotope ratios in the atmosphere, we can hope to learn something more about where the methane came from.
In the last few years, advances in laser spectroscopy have meant that we can now measure the isotopic composition of methane by shining lasers through a sample and measuring the absorption of certain wavelengths. However, the variations in methane isotope ratio that we expect to see in the atmosphere are very small. Therefore, to be able to resolve small changes, some people are proposing to also “pre-concentrate” air samples, which means that we remove a lot of the nitrogen, oxygen and other major components of air, to leave a more concentrated sample of methane that can be analyzed. Similar systems exist for measuring concentrations of other gases, but not yet for methane isotopes.
In this paper, we asked the question: “If we had these instruments at each AGAGE station, how much better would we be able to constrain methane emissions from different sources than we can at present?”. The answer we found was a little mixed. We found that these new measurements would provide additional information about the methane emissions to the atmosphere. However, the amount by which the uncertainties in our current estimates of methane emissions would be reduced is a little smaller than we hoped for. For example, for wetlands (the single largest source) and other microbial sources, we found that global uncertainty reduction would be reduced by only around 3%. For smaller sources that had a more “distinct” source isotope ratio such as biomass burning, larger relative uncertainty reductions were possible (9%).
Despite the relatively modest uncertainty reductions, my feeling is that, given the importance of methane in the global climate system, these new instruments will have a role to play in a future methane observing system. Given the complexity of the system, no single measurement (or modeling) strategy will be able to fully determine the causes of the strange changes we see in methane. However, by combining many measurement types, we should be able to understand the system better than we currently do.
Atmospheric Scientist at the University of Bristol