Presentation on theme: "HFCs: A Critical Link in Protecting Climate and the Ozone Layer A. R. Ravishankara Guus Velders Melanie Miller Mario Molina Steering committee headed by."— Presentation transcript:
HFCs: A Critical Link in Protecting Climate and the Ozone Layer A. R. Ravishankara Guus Velders Melanie Miller Mario Molina Steering committee headed by Joseph Alcamo Disclaimer: I am not talking as a co-Chair of WMO/ENEP SAP panel Opinions expressed are mine and not necessarily those of NOAA
Provisions of the MP led to decreases in ODS The Montreal Protocol is working and the ODSs are declining. HCFCs, the transition substitutes, are not contributing greatly to ozone depletion.
Montreal Protocols role in safeguarding the ozone layer. Current ozone layer depletions are small, except for the polar spring time ozone depletions. Ozone layer will recover in this century. Ozone hole will heal towards the end of this century. MP prevented major global ozone layer depletion Newman et al. WMO/UNEP SAP 2011
Montreal Protocol effectively protected climate ODS-Phase out led to a drop of ~ 8.0 GtCO 2 eq per year (1988 -2010). The avoided annual ODS emission (~ 10 Gt CO 2 eq in 2010 alone) - x5 the Kyoto target for 2008-2012 (1 st commitment period). ODS decrease: one of the largest intentional global GHG emission reductions to date
Montreal Protocol led to HFC use MP successfully phased out CFCs and is phasing out HCFCs. Phase out done via use of substitute chemicals or other approaches HFCs are the main replacements in many ODS applications
Use of HFCs is increasing Consumption of HFCs is increasing rapidly Consequent atmospheric growth rate of some HFCs are increasing very rapidly (some as much as 10% per year) The current contributions of HFCs to radiative forcing is still small (<1% of GHGs)
Climate benefits of Montreal Protocol may be lost because of growth in HFCs Unabated, future HFC emissions may offset climate benefit of MP. HFC emissions expected could be ~3.5 to 8.8 Gt CO 2 eq in 2050. Roughly equivalent to: - ODS annual emissions drop of 8.0 GtCO 2 eq per year for 1988 -2010 - 7 to 19% of the CO 2 emissions in 2050 (SRES) - 18 to 45% of CO 2 emissions for the 450 ppm CO 2. There is, of course, inherent uncertainty in such projections.
HFCs contribution to climate change by future emissions can be large Unabated, future HFC contribution radiative forcing can be large. Radiative forcing by future HFC emissions can be ~25% of that of CO 2 future emissions (SRES scenarios). Future HFC emissions can significantly hinder the 450 ppm stabilization target.
Low GWP-HFCs can retain climate benefits of MP. Currently HFC contrbute <1% of the total radiative forcing. HFCs are not all the same! Many HFCs (with shorter lifetimes) have very low GWPs. There do not appear to be other major environmental problems with the use of very low GWP HFCs. Possible to retain a <1% contribution in 2050 using low-GWP HFCs (GWP <20) and other alternatives, even for the upper range emissions Scenarios.
Summary MP effectively protected climate. HFCs were introduced mostly because of MP Currently HFCs are not significant for climate forcing Future climate forcing by HFCs can be very large because of using high-GWP HFCs There are many ways to reduce the climate influence of high- GWP HFCs Thank you for your attention & Over to Dr. Melanie Miller