Abstract
Abstract. A Reference Case (RC) scenario for emissions of HFC-23 from co-production during HCFC-22 manufacture over the next 25 years is presented. Offered as a template rather than a prediction, this model projects current production practices and existing abatement frameworks to yield insights into how atmospheric composition and radiative forcing might change with and without additional efforts to constrain HFC-23 emissions. Assuming that no additional abatement measures are implemented, emissions for year 2035 in this Reference Case would rise to 24 ktonnes yr−1, (cf., 8.6 ktonnes yr−1 in 2009), the atmospheric abundance of HFC-23 would rise to 50 ppt, which is a 121 % increase over the 2009 observed abundance, and HFC-23 would be expected to contribute a radiative forcing of 9 mW m−2 (cf., 4 mW m−2 in 2009). Under such a scenario, the HFC-23 emission growth rate would be a continuation of the historical trend of ∼0.2 ktonnes yr−2 until 2030, after which the growth is projected to quadruple as the Montreal Protocol phase-out of HCFC production for dispersive use concludes and HFC-23 thermal decomposition in the projects of the Clean Development Mechanism (CDM) comes to a scheduled end while growth in the production of HCFC-22 for feedstock use continues to climb with projected GDP growth. Two opposite variations regarding the future renewal of CDM projects are examined for their impact on projected emissions and abundance, relative to the Reference Case scenario.
Highlights
Hydrofluorocarbon-23 (HFC-23, known as CHF3, trifluoromethane and fluoroform) is a long-lived and potent greenhouse gas (GHG) with a global warming potential (GWP) of 14 800 for a 100-year horizon (Forster et al, 2007)
The Less Mitigation (LM) scenario illustrates the change in HFC-23 emissions that may result if the twelve Clean Development Mechanism (CDM) projects that opted for seven-year crediting periods are not renewed after their first terms
We use this scenario of globally installed HFC-23 thermal decomposition as our Best Practices (BP) scenario, and suggest that it results in a lower limit for future HFC-23 emissions, and its atmospheric abundance and radiative forcing
Summary
Hydrofluorocarbon-23 (HFC-23, known as CHF3, trifluoromethane and fluoroform) is a long-lived (atmospheric lifetime ∼270 years, WMO 2010) and potent greenhouse gas (GHG) with a global warming potential (GWP) of 14 800 for a 100-year horizon (Forster et al, 2007). With simple assumptions, we extend these bottom-up components along plausible pathways to create a Reference Case (RC) scenario of global HFC-23 emissions projected through the 25 years This particular period is of interest in that its terminus (year 2035) is slightly beyond the concluding phase of the 2007 HCFC-related revisions to the Montreal Protocol, which bring global production and consumption of HCFC-22 for dispersive uses essentially to an end. It coincides with the current term limits for renewable agreements for incineration of HFC-23 co-produced in the CDM projects.
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