Hydrofluorocarbons (HFCs) are replacements for chlorofluorocarbons (CFCs), the use of which is being phased out because they are primarily responsible for depleting the ozone layer. While HFCs don't destroy ozone, they are often very powerful greenhouse gases, so it is important that we monitor their concentration and emissions. One difficulty in doing this is that there are many HFCs emitted into the atmosphere, and new ones are appearing all the time.
To keep track of these gases, the AGAGE network has developed a system that can measure gas concentrations using mass spectrometry. The system is able to detect gases at very low concentrations, by removing most of the nitrogen and oxygen from the measured samples, increasing the concentration of the pollutants we want to measure. This means that we can now detect 'new' gases very soon after they appear in the atmosphere.
In this paper, our colleague Martin Vollmer from Empa in Switzerland describes the measurement of four HFCs that have appeared in the atmosphere over he last decade or so (HFC-227ea, HFC-236fa, HFC-245fa, HFC-365mfc). Using a combination of in situ measurements, and new measurements of archived air samples, we can determine the entire air history of the four gases, from the year they first appeared in detectable amounts.
Using these observations, and a two-dimensional model of the atmosphere, we calculated the annual global emission rates. As is often the case, the emissions we found differed from previous "bottom-up" estimates by substantial amounts, highlighting the value of this type of 'top-down' emissions verification.
For more information on GHG emissions modeling see web.mit.edu/mrigby.
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| Measurements of four new HFCs made by the AGAGE network. |
To keep track of these gases, the AGAGE network has developed a system that can measure gas concentrations using mass spectrometry. The system is able to detect gases at very low concentrations, by removing most of the nitrogen and oxygen from the measured samples, increasing the concentration of the pollutants we want to measure. This means that we can now detect 'new' gases very soon after they appear in the atmosphere.
In this paper, our colleague Martin Vollmer from Empa in Switzerland describes the measurement of four HFCs that have appeared in the atmosphere over he last decade or so (HFC-227ea, HFC-236fa, HFC-245fa, HFC-365mfc). Using a combination of in situ measurements, and new measurements of archived air samples, we can determine the entire air history of the four gases, from the year they first appeared in detectable amounts.
Using these observations, and a two-dimensional model of the atmosphere, we calculated the annual global emission rates. As is often the case, the emissions we found differed from previous "bottom-up" estimates by substantial amounts, highlighting the value of this type of 'top-down' emissions verification.
For more information on GHG emissions modeling see web.mit.edu/mrigby.
