Recent Increases in Global HFC-23 Emissions and the Contribution of HFCs and HCFCs to Radiative Forcing
S. Montzka1, L. Kuijpers2, M. Battle3, M. Aydin4, K. Verhulst4, E. Saltzman4, D. Fahey1, B. Miller5, L. Miller6, C. Siso5 and B. Hall1
1NOAA Earth System Research Laboratory, 325 Broadway, Boulder, CO 80305; 303-497-6657, E-mail: stephen.a.montzka@noaa.gov
2Eindhoven Centre for Sustainability, Technical University Eindhoven, Eindhoven, Netherlands
3Department of Physics and Astronomy, Bowdoin College, Brunswick, ME 04011
4Department of Earth System Science, University of California, Irvine, CA 92697
5Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309
6Science and Technology Corporation, Boulder, CO 80305
Trifluoromethane (HFC-23) is an unintended by-product of chlorodifluoromethane (HCFC-22) production and has a 100-yr global warming potential of 14,800. Firn-air and ambient air measurements of HFC-23 from three firn sampling excursions to Antarctica between 2001 and 2009 have been used to construct a consistent atmospheric history for this chemical in the Southern Hemisphere. The results show continued increases in the atmospheric abundance of HFC-23 and they imply substantial increases in HFC-23 global emissions since 2003. These emission increases are coincident with rapidly increasing HCFC-22 production in developing countries and are observed despite efforts in recent years to limit emissions of HFC-23 through the Kyoto Protocol’s Clean Development Mechanism. These results will be considered along with new NOAA measurements of additional hydrofluorocarbons (HFCs) from archived air, firn air, and ongoing flask-air measurements. Summed together, hydrochlorofluorocarbons (HCFCs) and HFCs accounted for 2.2% of the direct radiative forcing from all anthropogenic, long-lived gases in 2008, but they accounted for ~9% of the increase in total forcing from trace gases during 2003-2008. The increase in radiative forcing from HCFCs and HFCs was slightly larger than attributable to N2O global mixing ratio increases over this same period.
Figure 1. Global HFC-23 emissions derived from Antarctic firn air and ambient air measurements compared to augmented emissions reported to the UNFCCC by developed countries (blue line). The difference is attributed to developing countries (black line). HFC-23 emissions avoided through Clean Development Mechanism (CDM) projects of the Kyoto Protocol have been added to global emissions (green dashed line) to provide a picture of the ‘world avoided’ by these activities.
Figure 2. Radiative forcing from HFCs and HCFCs in recent years based on samples regularly collected at remote sites throughout the globe, archived samples from the Northern Hemisphere, and firn-air collected in Antarctica.