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
10
Lower atmospheric Cl+Br
8
Lower Atmospheric Cl+Br (PPb)
Without Montreal
Protocol
6
4 HCFCs
CFCs, Halons, Others
2
Natural CH3Br and CH3Cl
0
1950 1970 1990 2010 2030 2050
Year
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.
Newman et al. WMO/UNEP SAP 2011
MP prevented major global ozone layer depletion
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.
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
60
HFC abundances
50
40
Abundances (ppt)
30
20 HFC -134a
HFC -125
10
HFC -143a
0 HFC -152a
1990 1995 2000 2005 2010
Year
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