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Into the Future with Metrology - The Challenges of Our Environment and Climate


Human influences on the greenhouse gas cycle

carbon cycle
The global cycle ensures a constant change between bound and re-released carbon dioxide. (Fig.: Ernst Klett Verlag, Stuttgart, Wolfgang Schaar, Grafing, based on Barbara W. Murck et al.: Dangerous Earth. John Wiley & Sons Inc. 1997, p. 25)
Radon flux
Radon flux above Europe: between climate observation and radiation protection

Human civilization disturbs the natural cycle of the greenhouse gases (GHGs) like CO2, CH4, N2O and H2O. The concrete anthropogenic impact can be determined using various methods. When measuring GHG isotope signatures, advantage is taken of the fact that the ratio of different isotopes of an element can differ according to their origin. For example, the CO2 produced during combustion of plants and fossil fuels (= ancient plants) has a different ratio between 12C and 13C than the CO2 in the atmosphere. Methane is a greenhouse gas 30 times stronger than CO2 which comes from thawing permafrost, natural gas production, leaks in natural gas pipelines and intensive livestock farming. Here, different C/H isotope signatures are found. The same is true for the N isotopes in N2O, which is mainly influenced by intensive agriculture and traffic emissions, or for the H/D and 16O/18O isotope distribution in water. The latter is an important indicator of transport processes between the oceans, the atmosphere and the biosphere, and for condensation processes in clouds. In order to determine such isotope ratios on a global scale in the long term and with high accuracy, new reference materials and primary isotope ratio measurement methods for the different molecules are needed. In addition, optical transfer standards for traceability and mobile spectroscopic isotope measurements (e.g. on airplanes and balloons or at remote measurement sites) need to be developed or improved. Under field conditions, isotope ratios are currently determined mainly by optical/spectroscopic methods (laser or FTIR), which requires a robust metrological link between the optical measuring methods and the mass spectrometers, which are usually only operated in stationary mode. PTB works intensively with both methods. In EMPIR projects such as SIRS and STELLAR, PTB’s work aims at supporting the Global Atmosphere Watch Programme of the WMO and of the European Metrology Network (EMN), "Climate and Ocean Observation (COO)". Another innovative method is the radon tracer method. This method uses the naturally occurring radioactive noble gas isotope 222Rn (radon), which originates from the soil and is therefore, in deeper layers of the atmosphere, found in higher concentrations than in higher layers. 222Rn can therefore be used to obtain data for transport calculations (e.g. of CO2) and to validate models for calculating dispersion in the atmosphere. In this way, data for climate models will be available in the future with smaller uncertainties, allowing a distinction to be made between natural and anthropogenic greenhouse gases. For this purpose,  Opens external link in new window"traceRadon" a European model project coordinated by PTB, is offering traceability to the SI for the first time for the rapidly growing number of users of flux measurements around the world such as ICOS or ANSTO. In addition, outdoor air measurements of 222Rn provide a valuable database for efficiently improving the radiation protection of the European population without driving up the costs involved.

Participating departments and division

Opens internal link in current window3.1 3.1 General and Inorganic Chemistry

Opens internal link in current window 3.4 Analytical Chemistry of the Gas Phase

Opens internal link in current window6 Ionizing Radiation