Current Trends in Halocarbons: Impact on Climate Change

The two seminars explore the current state-of-the-art on our knowledge about contribution of anthropogenic halogenated organic compounds to atmospheric chemistry and climate change.  Results from a collaboration between Scuola Normale Superiore and University of Reading, established within the National Ph.D. program on Sustainable Development and Climate Change, are presented showing that climate change studies require the synergic efforts of different, apparently disconnected, disciplines, ranging from atmospheric physics to spectroscopy and quantum chemistry.

Keith Shine | Department of Meteorology, University of Reading
Halocarbons and climate change How well do we understand their contribution? 

Halocarbon gases, such as chlorofluorocarbons (CFCs) and hydrofluorocarbons (HFCs), have many industrial and domestic uses, including, for example, in refrigeration and air conditioning systems. Their potential contribution to climate change has been recognized for about 50 years, but there remain many unresolved issues which will be highlighted in this talk. These include (i) the fact that stratospheric ozone depletion due to CFCs causes a climate effect that opposes their direct contribution to the greenhouse effect, which means that their net contribution to climate change remains an uncertainty; (ii) there are several tens of such halocarbons detected in the atmosphere – some are decreasing in concentration while others are increasing, largely in response to international agreements – and we have only incomplete quantitative understanding of the drivers of these changes.

Daniela Alvarado Jiménez | Scuola Normale Superiore and IUSS Pavia
Impact of changes in water vapor continuum and spectroscopic parameters on radiative efficiencies of halocarbons

This study evaluates how recent updates to the description of the so-called water vapor continuum and improvements in the spectroscopic parameters of atmospheric species affect the estimation of radiative efficiencies (RE) of halocarbons, particularly in the 0 – 500 cm⁻¹ infrared region. Using quantum-chemical simulations beyond the anharmonic treatment and experimental infrared absorption measurements for HFC-236fa, HFC-245fa, and HFC-43-10mee, the research refines the calculation of REs and radiative forcing curves. These findings improve the accuracy of halocarbon absorption characterizations and strengthen the reliability of radiative forcing assessments, supporting a better understanding of their climatic impact.

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