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Tuesday, June 21, 2011

Cape Grim Greenhouse gas website launched by CSIRO

The CSIRO and Australian Bureau of Meteorology have launched a website showing the monthly data for greenhouse gases measured at the windswept Cape Grim Station located in the path of the roaring forties on the west coast of Tasmania. Cape Grim is one of three important baseline atmospheric stations for measuring background greenhouse gases, the other two being Mauna Loa in the middle of the Pacific and Alert Weather Station on Ellesmere Island in the Canadian Arctic. About 15 other stations around the world also collect and track atmospheric emissions data.

Dr Paul Fraser, Leader of CSIRO’s Changing Atmosphere research group said at the launch on Monday "We've been measuring greenhouse gases in the atmosphere since the late 1970s...We thought it would be good for the Australian public, or anyone in particular, to access our site where we can show them the data as it is collected, basically on a monthly basis."

The website provides an entry point to explaining greenhouse gases with the initial graph showing the data trend from the 1970s to the present for CO2, and two other strong greenhouse gases - methane and nitrous oxide. Since the station first began measurements in 1976, carbon dioxide levels have increased by more than 15 per cent. Concentrations of methane and nitrous oxide at Cape Grim have also increased significantly since 1978 by about 20 and 8 per cent respectively. The graphs show both seasonal variation and inter-annual variability which corresponds with the El NiƱo-Southern Oscillation (ENSO) and volcanic eruptions.

But Cape Grim measures much more including CFCs and related gases which have contributed to ozone depletion and the ozone hole over Antarctica each year. The Montreal protocol came into force in 1989 to phase out Chlorofluorocarbons which were destroying the atmospheric ozone layer and you can see a clear trend of these gases plateauing and starting to decrease as the CFC phaseout continues.

The datasets upon which all these graphs are based will eventually also be published on the site said Dr Fraser. Accurate data has been collected from Cape Grim since 1976. To graph concentrations on a longer time scale air samples collected from Law Dome in Antarctica are used to provide a record stretching back 1000 years.

In the past the data from Cape Grim has only been available indirectly through the data archived on a global level with the US Department of Energy and the WMO. The Japan Meteorological Agency maintains a World Data Centre for Greenhouse Gases for the WMO.

Peta Ashworth, Leader of CSIRO’s Science into Society Group said "Our group has been researching public perceptions to climate change for some time. Last October we ran a survey about communication and climate change and one of the things that came up was that the majority of people were very keen to learn more about climate change and climate change science, to become better informed and get more knowledge to make a difference. I think this website is one way for those that are interested. It provides an opportunity to see whats happening with atmospheric levels."

The primary graph displays the rising CO2 atmospheric concentration, but it doesn't give information on the proportion of CO2 that is anthropogenic or natural. In answer to a question about this Dr Fraser explained

"Simply seeing an increase in CO2 concentration in the atmosphere doesn't tell you where the carbon comes from. As a clue you can estimate how much of that carbon is in the atmosphere and what does that represent about what we know about the burning of fossil fuels. You see that the numbers are not widely different. There is some indirect evidence of the role of fossil fuels."

"The direct evidence is a combination of things. We just don't measure the concentration, we also measure the isotopic composition of the CO2. And the isotopic composition clearly shows it cannot be volcanic. The volcanic CO2 we know is a relatively small emission, because we have measured emissions from volcanoes and we know it has a certain isotopic signature which is completely different than the isotopic signature of CO2 coming from fossil fuels."

"The other think we measure is the oxygen levels in the atmosphere and the thing we show there is the increase in CO2 in the atmosphere is mirrored by a decrease in the oxygen level in the atmosphere. If the CO2 goes up 30ppm we observe a similar decrease in the oxygen. That is clearly indicative of a combustion process."

The provision of this data, initially in graph form on a monthly update basis but eventually as full datasets, provides a measure of public transparency and communication on atmospheric measurements of greenhouse gas emissions which is vital for the important public policy issues being debated on climate mitigation and climate adaption.

Climate tipping point: Global Atmospheric Methane on the rise - Jan 8, 2010 - The concentration of methane in the atmosphere is rising, according to measurements made by the New Zealand National Institute of Water and Atmospheric Research (Niwa) at its Baring Head Station near Wellington.

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