Present state of the ozone layer
and prospects for its recovery
Sophie Godin-Beekmann
LATMOS-IPSL,
UPMC/CNRS
1
Spectroscopy of ozone and related atmospheric
Outline
•
Ozone equilibrium in the stratosphere
•
Polar ozone destruction
•
Present state of the ozone layer
•
Ozone – climate interaction
•
Evolution of ozone depleting substances
•
Prospectives of ozone recovery
•
Impact on surface UV radiation
•
Dual benefit of the Montreal protocol
Spectroscopy of ozone and related atmospheric species,
2
The ozone layer: climatological
features
Ozone vertical distribution
Global distribution
90%
10%
•
•
Large ozone variation at synoptic and seasonal scale (> 100 DU) at mid
and high latitude
Since the 80s, ozone hole in October over Antarctica (< 220 DU) and
variable year-to-year decrease of ozone maximum over the North Pole in
3
Spectroscopy of ozone and related atmospheric species,
March
Ozone equilibrium in the atmosphere
Chemical processes
Efficiency of
catalytic cycles:
partition between
radicals and
reservoirs species
Dynamical processes
Ozone transported to higher latitudes by
the Brewer-Dobson circulation
winter
summer
Anthropogenic perturbation: emission of chlorine and bromine
compounds (CFCs and Halons): chlorine content multiplied by 5 in
the stratosphere, bromine increase: 80 %
4
Spectroscopy of ozone and related atmospheric species,
Polar ozone depletion
1 October 2011
Spectroscopy of ozone and related atmospheric
5
Ozone hole discovery in Antarctica
Early 80s
Syowa
•
Profil d’ozone
At Halley Bay, ozone total content
decreases systematically in October
Farman et al., Nature, 1985
At Syowa, ozone sondes
observations show very small ozone
values at 16-18 km
Chubachi et al., QOS, 1984
Spectroscopy of ozone and related atmospheric species,
During
winter
within the Polar
Vortex
Late
winter
Spring
Other cycle
involving
bromine
compounds
7
Spectroscopy of ozone and related atmospheric species,
Destruction
rate: ~4 %
Evolution of the Antarctic ozone hole
Spectroscopy of ozone and related atmospheric species,
8
Evolution of ozone hole
characteristics
Ozone hole area and minimum
2002
ozone
Exceptionnal
event:
Major warming
2002
Spectroscopy of ozone and related atmospheric species,
9
Ozone depletion in Arctic regions
Spectroscopy of ozone and related atmospheric species,
10
Evolution of Arctic Ozone Depletion
Winter
2004/2005
Ozone loss
PSC Volume
Cold winters: more stratospheric clouds, larger ozone depletion
Spectroscopy of ozone and related atmospheric species,
11
Record Arctic ozone depletion 2011
IASI total ozone
Manney et al., Nature 2011
Spectroscopy of ozone and related atmospheric species,
12
Present state of the ozone layer
Spectroscopy of ozone and related atmospheric
13
Ozone observations: Total ozone data
• Ground-based
‐ Longest time series: Dobson and
TOMS&SBUV
record
Brewer spectrometers
‐ DOAS/SAOZ spectrometers
‐ FTIR ozone time series in Europe
• Satellite
‐ TOMS: record taken over by OMI
since 2004
‐ TOMS & SBUV/2 retrieval version 8
Spectroscopy
of ozone and related
atmospheric species,
GOME, GOME-2,
SCIAMACHY
14
Ozone evolution at global scale
Annual ozone anomalies
•
•
•
•
•
•
•
Deasonalization with respect to
1979-1987
Substraction of 1964-1980
anomalies
Very little change since
2000
NH and SH ozone stabilize
at ~3.5 and 6% below pre1980
No sign of recent increase
Decrease larger in winter
at mid-latitudes
In the tropics : increase of
~0.5% in last
few years
15
Spectroscopy of ozone and related atmospheric species,
Global ozone trends
Search for positive significant trend
Increasing EESC
55°-60°N
- EESC
•
•
•
PWLT
TOMS and SBUV TO3 data
linear trend for declining part of
Equivalent Effective Strat. Chlorine
(EESC, yellow lines) compared to
second increasing slope of
Piecewise Linear Trend fit (PWLT,
blue line)
Decline of EESC: 0.34 ppbv/decade
Decreasing EESC
Other climatic effects
Light grey area for PWLT: 95%
confidence interval
Spectroscopy
ozone
and related atmospheric species,
From Vyushinofet
al., 2007
•
Significant
16
trend
Profile ozone data
• Ground-based
‐ Ozone Sondes: quality assessed ~ 5 to 10%
difference depending on manufacturers and sensing
solution.
‐ Umkehr : UMK04 retrieval, mainly in NH, low resolution
‐ NDACC lidar (high resolution) and microwave
spectrometers (low resolution)
‐ FTIR ozone profile retrieval (low resolution)
• Satellite
‐ Stable SAGE II and HALOE long term records stopped
17
in 2005 of ozone and related atmospheric species,
Spectroscopy
Ozone evolution at 40 km altitude
In the high stratosphere, ozone
depletion is due to homogeneous
chemistry only
Ozone anomalies between 35 – 45
km at NDACC lidar stations
•
Observed data: 5 month running mean
•
Satellite: zonal average
•
•
Grey area: CCMval simulation, 24
month running mean ± 2 σ
Extension from Steinbrecht et al., 2009
Stabilization
of O3 at a low level
Spectroscopy of ozone and related atmospheric species,
18
Ozone profile trends
Increasing part
of EESC (up to
1996)
Decreasing part
of EESC (from
1996)
Spectroscopy of ozone and related atmospheric species,
19
Evolution of ozone in the polar regions
Minimum ozone as a
function of equivalent
latitude
2011
increase?
x
Zonal
average
Spectroscopy of ozone and related atmospheric species,
no
increase
20
Ozone-climate interactions
Spectroscopy of ozone and related atmospheric
21
Ozone – climate interactions
transport
•
•
•
Stratospheric temperature determined by concentrations of radiatively active
gases (ozone, long-lived greenhouse gases, H2O) and aerosols via absorption of
SW and LW radiation
Transport determines amounts of stratospheric ozone and related long-lived
compounds
Temperatures influence temperature-dependent chemical reaction rates
Sun drives radiative, dynamical and chemical processes affecting ozone and
22
Spectroscopy
temperature of ozone and related atmospheric species,
•
Evolution of stratospheric aerosols
•
•
•
No increase in background aerosol up to
2000
Tenfold increase of aerosols due to large
volcanic eruptions (e.g. El Chichon,
Pinatubo)
Increase of background aerosol since 2000:
~ 4-7% per year possibly due to small
volcanic
eruptions and increased coal burning
Recent upward
trend
Spectroscopy of ozone and related atmospheric species,
23
Evolution of stratospheric temperature
Global mean temperature
anomalies from multiple
data sets 10 – 25 km
SSU temperature
anomalies
34-52 km
38-52 km
•
•
•
•
Global-mean lower stratosphere cooled
by 1–2 K from 1980 to 1995
Upper stratosphere cooled by 4–6 K from
1980 to about 1995.
No significant long-term trend since 1995.
Cooling of stratosphere due to
stratospheric ozone depletion and GHG
increase
26-46 km
20-38 km
21-39 km
Spectroscopy of ozone and related atmospheric species,
24
Stratospheric water vapor
water vapor tape-recorder signal
•
•
•
No recent increase in water vapor at Northern mid-latitude
Decrease in Tropical lower-stratospheric water vapor amounts by 0.5
ppmv around 2000 with low values observed ever since
Mechanisms driving long-term changes in stratospheric water vapor
not well understood.
Spectroscopy of ozone and related atmospheric species,
25
Evolution of Brewer-Dobson
circulation
Simulated annual mean upward mass flux at 70
hPa
•
•
•
•
CCMs predict an increase
of stratospheric BD
circulation due to increased
GHG
-> would induce a decrease
of total ozone in the tropics
and increase elsewhere
Cause of increase unclear
Observational evidence is
lacking so far
SPARC CCMVAL, 2010
Spectroscopy of ozone and related atmospheric species,
26
Impact of stratospheric ozone
depletion on climate
Major effects:
•
Southward shift of the SH mid-latitude jet in the troposphere in summer
due to Antarctic ozone hole
•
-> summertime trends in surface winds, warming over the Antarctic
Peninsula, and cooling over the high plateau.
Trend of annual near surface
temperatures
Other less robust effects:
•
Increase in sea ice area
around Antarctica
•
Southward shift of SH storm
track
•
Decrease of carbon uptake
over the Southern Ocean.
Spectroscopy of ozone and related atmospheric species,
27
What happens next to the ozone
layer?
Spectroscopy of ozone and related atmospheric
28
Stages of ozone recovery
Next issue
Spectroscopy of ozone and related atmospheric species,
29
Evolution of EESC
Equivalent effective stratospheric
chlorine
Total chlorine
abundance at
Jungfraujoch (x1015
Montreal protocol:
•
Total bromine in the stratosphere hasmol.cm-2)
started to decrease slowly
since 2008
•
Total chlorine continue to decline since ~2000 depending on
latitudes
•
Rate of decline depends on atmospheric lifetime of halogen
30
Spectroscopy
of ozone and related atmospheric species,
compounds
CCM prediction in the polar regions
•
•
•
Spectroscopy of ozone and related atmospheric species,
Antarctic: return of
total column ozone
to 1980 projected
after mid century,
later in other
regions
Arctic: return of
March-mean Arctic
total column ozone
projected in 20202035
In both cases,
ozone amounts will
exceed pre-1980
levels afterwards
31
CCM predictions in the tropics and
mid-latitudes
•
•
•
•
NH midlatitudes: return of TO3 to 1980
levels between 2015 and 2030. Superrecovery due to increased poleward transport
SH midlatitudes: between 2030 and 2040.
Tropics: decrease of TO3 due to increased
upwelling
Increase of ozone at 40 km due to slowing of
destruction reactions
Spectroscopy of ozone and related atmospheric species,
32
Surface UV radiation
Erythemal irradiance yearly
average
8 European stations
clear sky
conditions
all sky
condition
s
•
•
UV irradiance from clear-sky UV observations at unpolluted ~
constant since the late 1990s
Surface UV also influenced by oather factors: aerosols, clouds
Spectroscopy of ozone and related atmospheric species,
33
Dual benefit of the Montreal protocol
CFCs powerful greenhouse
gases
Evaluation of avoided CO2
equivalent emissions avoided
by the Montreal protocol:
11 Gt equivalent CO2 yr-1
avoided in 2010
5 times the objectives of the
Kyoto protocol
Velders et al., 2007
Spectroscopy of ozone and related atmospheric species,
34
Conclusions
•
•
•
•
•
Montreal protocol successful in reducing the amount of
ozone depleting substances (ODS) in the atmosphere but
the return to pre-1980 levels will take decades
The ozone layer has stabilized since the end of the 1990s at
~4% below pre-1980 levels at global scale (90°S-90°N)
Antarctic ozone hole is a recurrent seasonal feature since
1980, which had an impact on the Southern Hemisphere
climate
Arctic ozone depletion variable, strong depletions in the last
decade, record loss in 2011
The ozone layer will return to pre-1980 levels by 2020 –
2060 depending on latitudes
35
In polar of
regions,
competition
between
stratospheric
Spectroscopy
ozone and
related atmospheric
species,
•
cooling
Thank you !
Spectroscopy of ozone and related atmospheric
36