Scientific Assessment of Ozone Depletion: 2014

Chapter 5 Scientific Summary

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Scientific Summary Chapter 5: Scenarios, Information, and Options for Policymakers

A new baseline scenario for ozone-depleting substances (ODSs) is presented in Chapter 5 that reflects our current understanding of atmospheric mixing ratios, production levels, and bank sizes. Elimination of future emissions, from either production or existing banks of various ODSs, is applied to this scenario to evaluate the maximum impacts of various hypothetical policy options including phase- outs and destruction (see Table S5-1). Some specific findings corresponding to this table include:

Table S5-1. Summary of mitigation options for accelerating the recovery of the ozone layer and reducing CO2-equivalent emissions.

The table gives the reductions in integrated EESC (Equivalent Effective Stratospheric Chlorine) and integrated CO2-equivalent emissions relative to the baseline scenario that can be achieved for mitigation options beginning in 2015 or 2020. The integrated EESC is defined as the total EESC amount integrated from 2015 until the time EESC returns to the 1980 level (before 2050 for all scenarios). Bank recapture and destruction is assumed to be 100% effective and either applies to the bank existing in 2015 or the bank existing in 2020. Any potential contribution from very short-lived substances is neglected. These calculations use the lifetimes derived from SPARC, 2013 (Stratosphere-troposphere Processes And their Role in Climate).

Substance or Group of SubstancesReductions (%) in Integrated Midlatitude EESC Integrated from 2015 until EESC Returns to 1980 LevelsReduction in Cumulative GWP- Weighted Emissions from 2015 to 2050 (Gigatonnes of CO2- equivalent)
Bank recapture and destruction in 2015 or 2020:2015 bank2020 bank2015 bank2020 bank
Production elimination from 2015 onward:
(only quarantine and pre-shipment)
Total emissions elimination from 2015 onward:
HFCs0.0Up to 165*

* Reduction relative to hypothetical future upper range scenario and would depend on actual growth rate of HFC use.