KLIMAFORSK-Stort program klima

Halocarbon gases present in the atmosphere (chlorofluorocarbons - CFCs and their replacements) are normally associated with stratospheric ozone depletion, yet they are strong greenhouse gases that have substantial impacts on radiative forcing of climate c hange. Their impact on climate varies considerably, depending specifically on the atmospheric lifetime and radiative forcing efficiency of each compound. To set restrictions on emissions for the purpose of mitigating climate change, it is important to hav e adequate knowledge about the properties of each gas to derive their climate impact, which is normally quantified in terms of metrics, such as Global Warming Potentials (GWPs). Working Group I of the Intergovernmental Panel on Climate Change (IPCC) rece ntly released their 5th Assessment Report (AR5) (IPCC, 2013). The number of halocarbon gases included in the list of metric values was more than doubled compared to the previous IPCC assessment report (AR4), largely due to the publication of a comprehensi ve review study of GWPs for halocarbons and related compounds (Hodnebrog et al., 2013). At a workshop in Oslo in May 2014, international experts in the field, including the author team of Hodnebrog et al. (2013), identified several issues for improvement and reporting of metric calculations of halocarbons. Concrete plans were made for how these issues could be approached, and will, if acted on now, lead to an improved and more comprehensive treatment of halocarbon metrics in the next IPCC assessment repor t, and also lead to better communication with policy makers and industry. A follow-up workshop in Oslo in 2015 would be an important and timely step to accelerate international collaboration on halocarbon metrics, and to ensure that policy makers are wel l informed. The main goal of the 2015 workshop will be to follow up on the research and communication programs begun at the Oslo workshop in May 2014, as well as identify any emerging issues.