HFCs: A Critical Link in Protecting Climate and the Ozone Layer

A. R. RavishankaraGuus Velders

Melanie MillerMario Molina

Steering committee headed by Joseph Alcamo

Disclaimer: I am not talking as a co-Chair of WMO/ENEP SAP panelOpinions 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 Protocol’s 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 GtCO2eq per year (1988 -2010).

The avoided annual ODS emission (~ 10 Gt CO2eq in 2010 alone)

- x5 the Kyoto target for 2008-2012 (1st 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 CO2eq in 2050. Roughly equivalent to:

- ODS annual emissions drop of 8.0 GtCO2eq per year for 1988 -2010- 7 to 19% of the CO2 emissions in 2050 (SRES)- 18 to 45% of CO2 emissions for the 450 ppm CO2.

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

CO2 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