The research activity covers topics related to gas analysis, humidity and temperature. Methods based on spectroscopy measurements and dynamic methods are used for absolute measurements and standard realization of gases influencing the climate at trace level (ozone, SF₆, VOCs). Gravimetric methods are developed for the preparation of standards for gases present in the atmosphere at higher concentration (as CO₂). Most of the results are obtained in the framework of international joint research programs promoted by CIPM and EURAMET.
Global climate models describe how the atmosphere, the oceans, the land, living things, ice, and energy from the Sun affect each other and the Earth's climate. Climate researchers use global climate models to better understand how global changes such as increasing greenhouses gases or decreasing Arctic sea ice will affect the Earth. Greenhouse gases (CO₂, H₂O) in our atmosphere allow the lower atmosphere to absorb heat that is radiated from the Earth's surface, trapping heat within the Earth system. The amount of greenhouse gases in our atmosphere is on the rise, causing temperature to climb.
Accurate knowledge of the concentrations of such gases and aerosols in the troposphere and their variability in time and space, as well an Earth temperature and humidity mapping, is essential to support scientific understanding of atmospheric photochemistry. The world standards for gases in the WMO-GAW-network and other air quality monitoring networks, should be hosted at NMIs that are members of CCQM/GAWG.

It plays a crucial role in the atmosphere. Whereas in the stratosphere it protects living organisms from harmful solar UV radiation, in the lower atmosphere at levels down to about 10^-9 parts per part of air it has an adverse effect on human health and plants.
Since 2004 INRIM has developed and mantained the ozone in air primary standard (INRIM-O3SRP), providing traceability to the 21 laboratories of the National Air Quality Monitoring Network. The standard is based on the UV linear absorption of the electronic band of the O₃ molecule. In 2007 experimental analysis allowed re-evaluation of the uncertainty of the primary standard: the Key Comparison CCQM-BIPM-QM-K1 "Ozone at ambient level" validated its uncertainty.
Traceability has been guaranteed at ARPA, environmental laboratories, CNR institutes (Antartic project), work-ambient control laboratories (contact: m.sassi@inrim.it).

It is one of the six gases regulated by the Kyoto protocol. It is a totally anthropogenic gas with a 500 year life time, present in the atmosphere at 10^-9 mol/mol level.
Studies for the development of a new generation of primary gas mixtures based on laser absorption spectroscopy have been performed on this gas. And an absolute determination of the amount of SF₆ in pure N₂ in the 10^-4 mol/mol range have been realized. The extended relative uncertainty is U = 0.03 nmol/mol (contact: m.sassi@inrim.it).

Reactive non-methane hydrocarbon compounds commonly referred to as VOCs, present in the atmosphere in fraction level within a range between 0.01 and 10 nmol/mol, play an important role in the chemistry and therefore the oxidizing power of the atmosphere. They are responsible for the photochemical formation of O₃ and other photo-oxidant pollutants. The realization of primary standards of some VOCs at ambient level is a challenge for the NMIs. An international project between WMO-GAW and CCQM-GAWG for the establishment of Central Calibration Laboratories for VOCs has been defined [3]; in 2007 a first exercise (EUROMET 886) that demonstrates the degrees of equivalence of the NMIs for ambient VOCs has been run on the analysis of the twenty-nine components requested by the EU directive 2002/3/EC. INRIM participated successfully in this comparison with GC-FID in cooperation with Politecnico di Torino and WMO-IKM_IFU (Germany)(contact: m.sassi@inrim.it).

In terms of total mass of emission, CO₂ is the single most important waste product of our industrialized society.
The CO₂ level over the last 1000 years was about 280 µmol/mol. By 2003 the global mean atmospheric CO₂ level had reached 375 µmol/mol. In recent years INRIM set-up a facility for primary gravimetric preparation of gas mixtures. CO₂ in N₂ and in air primary gas mixtures, both at atmospheric and at emission level, have been prepared and studies of their stability have been carried out. In 2007 the results of the international Key comparison CCQM K52 "Carbon dioxide in synthetic" and of a bilateral comparison with NPL, validated the gravimetrical preparation procedure (contact: m.sega@inrim.it).

Clouds are one of the most significant elements in the atmospheric system, playing several key roles. Some types of clouds may help warming, while others may help cooling. Precise water measurements are needed at global and at micro climate level. In both cases measurement are required up to 100% RH. At INRIM studies are in progress for developing standards and sensors working in a network configuration, traceable to primary humidity standards in the air temperature range from -25 ºC to 90 ºC (contact: v.fernicola@inrim.it).

[1] J. Viallon et al: "Intern. Comparison CCQM-P28: Ozone at ambient level", Metrol., Vol. 43, No 1A (Techn. Suppl.), 08010, 2006.
[2] M.P. Sassi: "Accuracy budget of amount-of-substance gaseous standards based on absorption spectroscopy", IEEE Trans. on Instrum. and Measur., Vol. 56, no. 2, pp. 564-566, 2007.
[3] E. Amico di Meane, M. Sega, F. Rolle: "International comparison CCQM-K52 "Carbon dioxide in Synthetic air" - INRIM results", INRIM Technical Report no. 32, October 2006.
[4] A.M.H. van der Veen et al: "Intern. comparison CCQM-P41 Greenhouse Gases. 1. Measurement capability", Metrol., Vol. 44, no. 08002, Techn. Suppl., 2007.
[5] A.M.H. van der Veen et al: "International comparison CCQM-P41 Greenhouse Gases. 2. Direct comparison of primary gas standard mixtures", Metrol., Vol. 44, no. 08003, Techn. Suppl., 2007.
[6] E. Amico di Meane, M. Sega: "Pilot study CCQM-P41 "Greenhouse gases"- IMGC results", IMGC Technical Report no. 114, 2004.