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Overview and Definitions

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The four monitoring stations in the UK and Ireland measuring greenhouse and ozone depleting gases are funded by the UK's Department of Energy and Climate Change (DECC). The University of Bristol has been running a programme of atmospheric monitoring of trace gases at Mace Head in the Republic of Ireland since 1987, with the UK Met Office carrying out interpretation of these data. In 2011, the Met Office and the University of Bristol (Atmospheric Chemistry Research Group) were awarded a contract to establish an expanded programme of atmospheric observations to deliver increased spatial and temporal resolution of the estimated emissions. The methodology chosen to achieve this was to establish two new tall tower observation sites based in Ridge Hill tower (Herefordshire) and Tacolneston tower (Norfolk), and to adopt an existing station: Tall Tower Angus (Scotland). The Angus site has since been replaced by a site at Bilsdale. The raw data from the Mace Head site is available from the CDIAC and the ratified raw observations from Ridge Hill and Tacolneston are available through the EBAS database (select UK_DECC framework). The most recent observations of CO2 and CH4 are also shown pictorially through the ICOS website for Ridge Hill, Tacolneston and Mace Head.
The atmospheric observations are used to derive hemispheric baseline atmospheric concentrations and UK emission estimates. The estimates are used to compare with the official UK greenhouse gas inventory as submitted to the UNFCCC (United Nations Framework Convention on Climate Change) as well as feeding into other research programmes, such as the EU projects INGOS (Integrated non-CO2 Greenhouse gas Observing System) and NitroEurope, and global networks such as AGAGE (Advanced Global Atmospheric Gases Experiment), of which Mace Head is a key station.
The Mace Head site is well positioned to contrast air entering Europe from the Atlantic with emissions leaving Europe towards the Atlantic, while the three UK sites provide excellent spatial measurement distribution thus enabling the Met Office to better determine emissions estimates for the UK and its Devolved Administrations (England, Wales, Scotland and N. Ireland). Mid-latitude Northern Hemisphere baseline monthly mass mixing ratios estimated from the Mace Head observations using the method described in Manning et al. 20111 are shown under Trends.


Global Warming Potential (GWP) - The ability of a greenhouse gas to trap heat in the atmosphere. It is measured relative to carbon dioxide (CO2) and is calculated over a specific time interval. For example, a gas with a GWP100 of 10 will trap 10 times as much heat as the same mass of CO2 over a 100 year period.

Atmospheric Lifetime - The mean length of time a given species resides in the atmosphere, determined by it's sources, sinks, reactivity and deposition rates.

Radiative Efficiency (RE) - A measure of the net energy change in the atmosphere caused by climatic factors. RE can be used to assess and compare anthropogenic and natural drivers of climate change.

Ozone Depletion Potential (ODP) - The ability of a chemical species to destroy stratospheric ozone relative to that of CFC-11, which is given a reference value of 1.

1. Manning, A.J., O'Doherty, S., Jones, A. R., Simmonds, P. G. and Derwent, R. G., 2011. Estimating UK methane and nitrous oxide emissions from 1990 to 2007 using an inversion modeling approach, J. Geophys. Res., 116, D02305. doi:10.1029/2010JD014763

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