A model calculation of the ozone response to the increase in the atmospheric emission of several gases

INSTITUT O AERONOMIE SPATIALE OE BELGIQUE 3 · Avenue Circulaire

B · 1180 BRUXELLES

A model calculation of the ozone response to the increase in the atmospheric emission of several gases

A preliminary Report

by

A. DE RUDDER and G. BRASSEUR

2.-

1. INTRODUCTION

A series of time-dependent, multiple perturbation calculations have been carried out using a 1-D chemical radiative model to describe the response of the ozone layer to the injection in the atmosphere of gases such as the chlorofluorocarbons (F-11 and F-12), CH

3cc1

3, CC1 4, Co

2, CH 4 and N20. The effect of nitric oxide released by the engines of aircraft is also considered in some model cases.

The purpose of this preliminary note is to briefly summarize the results obtained by this model. A number of graphs with the main model output is given hereafter. Full details of the calculations will be published in scientific journals.

The model which is used in the present work is one-dimensional and extends from the earth's surface to JOO km altitude. The chemical routine considers a number of species belonging to the O, HO, NO ClO

X X X X

and CO families. The chemical rate com:tanls are taken from the JPL

X

publication 1983. The vertical profile of these species is calculated from continuity equations in which the vertical flux is determined for a prescribed "eddy diffusion coefficient". The temperature which determines the local value of most reaction rates is self-consistently calculated by a radiative method which considers the absorption of the solar UV radiation by

o

3 and

o

2 and the infra-red transfer of terrestrial and atmospheric radiation by co

2,

o

3 and H

2

o.

A 50 percent cloud coverage is assumed, the top of the clouds being located at 5 km altitude.

2. EVOLUTION OF THE TRACE GASES AMOUNT lN THE PAST (1940-1983)

The following mixing ratios (f) or world emissions (E) with the corresponding references have been adopted as a function of time (t) in the model calculations.

3.-

Co2 mixing ratio

1940 ~ ~ 1957 f -4

[ .00141(t-1849)] ^{( 1)} t = 2. 7 x 10 exp

1957 < t ~ 1980 f 2.7 10- 4 -5

exp[.019(t-1957)] ⁽¹⁾

= ^X + 4.44x10

1980 < t ~ 1983 f = [(1980) x exp [.OOS(t - 1980)) (2)

N20 tropospheric mixing ratio :

1940

~

t

~

1980 f = 2.85 x 10-7

+ .14x10-7 exp[.04(t - 1977)) (1) 1980 < t ~ 1983 f = f(1980) x exp [ .002 (t - 1980)) (2)

CH4 tropospheric mixing 1940 ~ t ~ 1980 f =

ratio :

-6 -6

10 + .65 x 10 exp[.035(t - 1980 < t ~ 1983 f = [(1980) x exp [.Ol(t - 1980))

CH3

ccl

3 world emission 1940 ~ t ~ 1950 E

=

⁰

1950 < t ~ 1976 estimates from (3) 1976 < t ~ 1980 linear with time 1980 < t ~ 1983 E

=

500 kt/year

CC14 world emission

1940 ~ t ~ 1980 estimates from (4)

1979)) ⁽¹⁾ (2)

(2)

1980 < t ~ 1983 E = 100 kt/year (2)

CFC 11 and 12 world emission CMA values (see figure)

(1) D.J. Wuebbles, M.C. Mac Cracken and F.M. Luther, A proposed Refe- rence Set of Scenarios for Radiatively Active Atmospheric Consti- tuents, Prepared for the United States Department of Energy, DOE/

NBB-0066, October 1984.

(2) Working value (C.M.A).

(3) R.G. Prinn et al., The Atmospheric Lifetime Experiment. 5. Results for CH

3cc1

3 based on three years of data, J.G.R., 88, cl3, 8415- 8426, 1983.

(4) P.G. Simmonds et al., The A.L. Experiment. 6. Results for Carbon Tetrachloride based on 3 years data, J.G.R., 88, cl3, 8427-8441,

1983 (After 1958 : lower limit).

4.-

3. SCENARIOS FOR THE FUTURE (1983-2040)

Four scenarios running through to 2040 have been considered, which have certain assumptions about trends in non-CFC gases in common, but which differ in the CFC emission patterns.

a)

b)

c)

The assumptions about the non-CFC gases are as follows

co₂ - 0.5%/year exponential growth (as specified in the 1984 NAS report) (fig. 1) f = 340 x 10 -6 x exp [0.005 (t - 1980)]

N2o - 0.2%/year exponential growth. (fig. 2). f = 301 x 10 -9 x exp [0.002 (t - 1980)]

CH4 - 1%/year exponential growth (fig. 3) - this is at the conser- vative end of the generally accepted 1-2% year range. f = 1.67 x

10-6

x exp[O.Ol(t - 1980)]

d) CH 3CC1

3 - Constant emission at 500kt/year (fig. 4).

e) CC1

4 - Constant emission of lOOkt/year (fig. 4).

The CFC emissions for the four scenarios are shown graphically in figures 5 and 6; they are derived from the following productions :

1. Constant production on the basis of the year 1983 - the base line case.

2. Productions grow by 3% year until they reach 1.5 times current productions in 1997. This simulates the extension of the EEC production cap provision to a global scale.

3. Aerosol usage world-wide phased out over four years, but' other uses grow at 3% year until they reach 1.5 times current productions.

This simulates the aerosol ban proposed for the CFC protocol, associated with a global capacity cap equivalent to that prevailing in the EEC.

4. Identical to 3 but with the 3% per year growth allowed to continue indefinitely. This is equivalent to the protocol proposal which does not include a capacity cap.

5.-

500

-

^> _~

a.

450

-

Q. 0 t-~

a:

C)

400

z

><

~ UJ _~

350

: )

-' 0

>

3°9940

_{1980 1980 2000} 2020 TI ME ( YEARS)

Figure 1 Assumed volume mixing ratio for carbon dioxide as a function of time. Before 1980, the expression suggested by Wuebbles et al. (1984) has been adopted. An increase of 0.5'%, per year bas been assumed afterwards. The value in 1980 is 340 ppmv.

-

^>

_m

D.

-

D.

3 4 0 . . - - - -

TROPOSPHERIC N ₂ 0

0

320

1-,c(

a:

C)

z

) (

i ³⁰⁰

w

:E ::.,

_,

0 >

ZS0,1.!!i-9 '!"'!1'-..__1_9 .... so-... ^{_1 ... 9 ....} ao_..._....at_...,~~~---...

TIME (YEARS)

6.-

Figure 2 Adopted tropospheric volume mixing ratio for nitrous oxide as a function of time. The expression before 1980 is the estimate by Wuebbles et al (1984) and leads to a value of 301 ppbv in 1980. A 0.2% increase per year is assumed after 1980.

7.-

3.5

- ^>

::E

3.0 TROPOSPHERIC CH ₄

0.

-

0. 0

~ 2.5 a:

C.!)

z >< 2.0

-

::E

LLJ

::E ::::>

1.5

0 -'

>

1.0 1940 1960 1980

²⁰⁰⁰

20ZO 2040

TIME(YEARS)

Figure 3 Assumed increase in the tropospheric content in methane. The value before 1980 is taken from Wuebbles et al. (1984) and equals 1.67 ppmv in 1980. A 1% increase per year is adopted after 1980.

600r--r--r-,--,r--,.---~

400

....

CIC ~ . -!:.200

JC ~

....

0 z

II) II)

~ O t - - - - 1 i - - t - - + - - + - - - t - - + - - t - - 1 ~ ~ - _ .

•

..J ^:::) _z

z c 150

0

a: ..J 0

:l ¹⁰⁰

50

0 _ __..____., _ __,_ _ _.__...__..___._____._ ... _ _

191.0 1960 1980 1000 2020

TIME (YEARS)

8.-

Figure 4 Historical and assumed future emission of methyl chloroform and carbon tetrachloride. Estimates for the past are from the Atmospheric Lifetime Experiment (1983). A constant emission of 500 kt/yr for CH

3

cc1

3 and 100 kt/yr for CC1

4 is adopted after 1980.

9.-

1250

- ^ex

<II(

>

UJ

CFC 11

";:: 1000

-

X:

z

0

Cl)

7SO

Cl)

•

-

UJ ~ ..J

500

<(

::,

z

<(

z

0

250

..J

a:

0 ~

0 1940 1960 1980 2000 2020 2040

TI ME (YEARS)

Figure 5 Assumed scenarios for the emission of CFC1

3. The past emission (1945 to 1983) is derived from the production estimated by Gamleo et al. (1984). The future emission results from a constant production in scenario 1 and from a 3% yr increase in the production up to the level of 1.5 x its present value (reached in 1997) in scenario 2. Scenario 3 assumes the same increase except in the production of aerosols, which declines between 1983 and 1986; the same capacity cap as in scenario 2 is reached in 2008. Scenario 4 assumes the same conditions as scenario 3 but without any capacity cap.

- ^a: _-<

l&J

>

..._

I-~

-

10. -

1500 - - - . , . . _ - - - -

CFC 12

%1000

0 ,

•

1/) 1/)

-

~ l&J

-< _,

~ 500 z -<

0

_,

a: 0

3: 0

t...ae::c:::::..J._...11.-,...L_..,__Jl,._..J__.J.___Ji_...J

1940 1960 1980 2000 2020 2040

TI

ME

(YEARS)

Figure

6

Same as figure

5

but for

CF 2 c1

2 .

The decline in the production of aerosols assumed in scenarios 3 and 4 occurs only between 1983 and 1985.

11. -

The choice of a 3% growth rate is arbitrary and is intended to demonstrate the calculated effect on stratospheric ozone of future CFC growth. It is not in any sense a prediction that such a growth rate is occurring, or is likely to be sustained in the future. It should be noted that a 3% per annum growth rate up to the year 2040 would result in a five-fold increase in production, and would require around a four- fold increase in installed production capacity.

NUMERICAL VALUES

CFC13 world emission

scenario ^] 1983 ~ t ~ 2002 increasing 2002 < t ~ 2040 E

=

309 kt/year scenario 2 1983 ~ t ~ 2015 increasing

2015 < t ~ 2040 E

=

467.1 kt/year

scenario 3 1983 ~ t ~ 1987 decreasing (219.9 kt/year in 1987)

1987 < t ^~ 2027 increasing 2027 <t ^~ 2,040 E

=

464 kt/year scenario 4 1983 ~ t ~ 1987 same as scenario 3

1987 < t ~ 2040 increasing (1018.4 kt/y in 2040)

CF2Cl

2 word emission

scenario 1983 ~ t ~ 1995 increasing

1995 < t ~ 2040 E

=

421.8 kt/year scenario 2 1883 ~ t ~ 2009 increasing

2009 < t ~ 2040 E

=

638 kt/year

scenario 3 1983 ~ t ~ 1986 decreasing (327 kt/y in 1986) 1986 < t ~ 2020 increasing

2020 < t ~ 2040 E

=

639.5 kt/year scenario 4 1983 ~ t ~ 1986 same as scenario 3

1986 < t ~ 2040 increasing (1447 .3 kt/y in 2040)

12.-

4. MODEL RESULTS FOR THE PAST (1940-1983)

Figures 7-13 show results obtained for the historical release and increase of CFCs and other source gases. The predicted present day Cl

X

mixing ratio at 50 km is 2.4 ppbv (fig. 7). The change in the tempera- ture at different altitudes is given in fig. 8. The calculated absolute change in the ozone concentration at 40, 30 and 20 km is shown in figures 9-11. Relative variations of the ozone amount at selected alti- tudes is given in figure 12. The resulting change in the ozone column seems to be characterized by a small increase of 0.2 to 0.3 percent between 1940 and 1983 (fig. 13). This variation results from an ozone depletion in the upper stratosphere and an ozone enhancement below "' 30 km altitude.

5. MODEL RESULTS FOR THE FUTURE (1983-2040)

The following model predictions consider a simultaneous increase in

co2, N

20, CH

4 and in the CFC emission. For this last case, the 4 scenarios as described in section 3 have been adopted.

The predicted evolution in the CJ mixing ratio at 50 km is shown

X

in fig. 14. A value of the order of 6-8 ppbv is found in year 2040.

These numbers are lower than the values obtained in year 2080 when adopting the NASA scenarios (high CFC growth). [NASA report in pre- paration]. No "high chlorine regime" will be reached (before 2040) by any of the 4 presently adopted scenarios. The change in temperature is given by figures 15 and 16. The relative evolution of the ozone concen- tration at 50, 40, 30 and 20 km is represented in figures 17-20. One should note that the local behavior of ozone varies significantly with altitude and with the adopted scenario. The absolute and relative change in the ozone concentration as a function of altitude is displayed for scenario 1 in figures 2_1 and 22 respecli vely. The change in the ozone column for the 4 scenarios is shown in figure 23. A comparison between

2.25

- ^>

_(D

~

^2.00

-

₀

t-~ 1.75

z

C)

>< 1.50 :2:

w :2:

:::, 1. 25

...J

0 >

C Ix

50KM

1950 1960 1970

TI ME (YEARS)

13.-

1980

Figure 7 Amount of odd chlorine atoms at 50 km altitude, resulting from the dissociation of the assumed released chlorocarbons before 1983, as a function of time.

- _{~ or---•}

(.') LaJ

z

,c(

u :c

LaJ

-2 a::

:::,

....

a::

,c(

a.

LaJ

::E

LaJ -4

....

TEMPERATURE

1950 1960 1910

TI ME (YEARS)

KM 1

1990

14. -

Figure 8 Computed past temperature change from year 1940, as a function of time and at different altitude levels.

15.-

2 _ _

....,...,...,_..,...,_..,...,... _ __.. _ _ _ _ _ _ _ _ _ _

-

,., ·e 0

gV

0

-

^{) (}

-

_w

^-2 _OZONE

C)

z

"' ^{40 km}

:c u

z

^-4

0

~ a:

I-

z _-6

w

u

z

0

u -8

1940 1950 1960 t970 '980

TIME (Years)

Figure 9 Change in the ozone concentration at 40 km (from its 1940 value) corresponding to the adopted historical scenario, as a

function of time.

16.-

10

-

... ·e

u

°'2 _I

.!S

~ z

<C(

:c u 0

z

0

OZONE

-

....

<C(

....

a:

_{30 km}

t: z ^-5

0

z

u

-10

1....,1...,...1,_,___.___.__._-'-..,__.__ _____ .._..., _______ __

1940 1950 1960 1970 l980

TIME (Y.ars)

Figure 10 Same as figure 9, but at 30 km altitude.

17.-

10

-

.. E • ^OZONE

_.,

0

-

^IC

^{20 KM}

-

^Lt.I _(!)

⁶

◄

z

X

u ₄

g z

!c

~

2

t-

z

Lt.I

u

z

0 u 0

- 2 -... -_,_ _ _ _ _ _ _ _ _ _ _ _ _ ...., _ _ _ ....,

191.0 1950 1960 1910 1980

TIME (YEARS)

Figure 11 Same as figure 9, but at 20 ^km altitude.

- _.- ^• -

^UJ

~

⁰

<(

Uo :c -

...,.

o- zo, i=o

<( t-

-5 a::

UJ t-

>

z_

UJ t-

u

<(

z

..J

0 UJ Ua;

w - -10

>

....

<(

..J

UJ

a::

OZONE

KM 10

40

-15L...l'--'--"-'----'--'-...._..__ ...

^~

... ...

1940 1950 1960 1970 1980

TIME(YEARS)

18.-

Figure 12 Past relative ozone concentration change computed at different altitude levels.

19.-

0.2

-

^~

- _{z OZONE}

0

0.1

.::

_,c

TOTAL COLUMN

; -

l&J

>

.::

_,c

0

...J l&J

a:

-0.1 - - - -

1940 1950 1960 1970 1980

TIME (Y•ars)

Figure 13 Relative variation in the total ozone amount computed for the past (the initial value being the one of 1940).

20.-

8

-

_~1

a. Clx

a. SOKM

-

0

;:: 6

<

a:

C)

z5

><

::E

I.LI 4

:::, ::E

...J

0

>

3

2 ... __._ ...

...._..__.,_.__._J... ... _...,_..._. _ _ _ _ _ _ _ _ _ _

1990 2000 2010 2020

2030 2040

TIME (YEARS)

Figure 14 Cl volume mixing ratio at SO km altitude as a function of

X

time, due to the injection of chlorocarbons as assumed in the 4 different scenarios.

21. -

275 - _-

^X:

M

TEMPERATURE

^{0) CD}

270 50 KM ⁰

t-⁰

-

^x::

^w >

- ^w _a: ^- _{~ _,}

::>

w

t-

265 -5 ^a:

.I(

a:

UJ

UJ C)

Q.

z

~

..:

w :c

t-

u

260 ^-10

UJ

a:

::>

t-

..:

a: r

:I:

255 ^-19

^t-Ill

1990 2000 2010 2020 2030 2040

TI ME (YEARS)

Figure 15 Computed future temperature at SO km altitude, as a function of time, in the 4 different cases. The right-band scale indicates its change from 1983.

22.-

50

1960

- e

-

M

⁴⁰

l&J

g ...

TEMPERATURE

...

_-'

◄

SCENARIO 1 JO

-15

-Kl -5

0

TEMPERATURE CHANGE (K)

Figure 16 Computed temperature change relative to 1940, in the con- ditions of scenario 1, as a function of altitude and for different years.

- '1 _~

,c(

z

:x:

u z

Q - -s

~

,.,

0:

=

t- -

Zo

LaJ t-

u

ZLaJ

8 ;:-10

LaJ

=5

> LaJ

;:: 0:

,c( - ..I 0: LaJ

OZONE 50 km

23.-

-,s ...

...i ... - . . ... _ ... _ _ _ _ _ ..__..._. _ _ _ _ _ .._..., _ _ _ _ _ _ ,&_,j . . . _ _ _

1990 2000 2010 2020 2030 2040

TIME (Years)

Figure 17 Future relative ozone concentration change at SO km altitude, computed for the 4 different scenarios. as a function of time.

24.-

1

0,w-...,.-r-r-r-r-r-r _ __, __ ..., _ _ _ _

-r--.._...,,... _ _

- w

C)

z

~

:c

u z --10

0 ,., - CID

~

2?

0:: 0

...

z ww u >-20

0 ~

z -

u

^..J

WW

> ~

...

_~

w ..J 0::

OZONE

40 km

1990

2000 2020 2030

TIME CY•ars)

Figure 18 Same as figure 17 but at 40 km altitude.

2040

25.-

10

-

,., ·e

u

en 0

-

^JI( 5

-

_LI.I

<!)

z

<c(

u :c

0

0

z

~ OZONE

a: t-

30 km

z

LI.I

u

-5

0

z

u

-10

...,__,___,__.___,___,__,_...L--'--'--.L--.L.-L...J"--'--L--'-...L....L...L....U

1940 1950 1960 1970 1980

TIME (Y•ars)

Figure 19 Same as figure 17 but at 30 km altitude.

26.-

-

^{~ 0}

^It

-

(!)

w

OZONE

z

<(

:r 3 ^20km

u w >

t- -_<( C"")

_J

co

Wm

0:: -

2

zO

¹

0

t- t-

-w >

<( -

~ ~ z

J

1 WW u ^z

0::

-

0 u

0

1990 2000 2010 2020 2030 TIME (years)

Figure 20 Same as figure 17 but at 20 km altitude.

-

^2:

⁴⁰

:::c:

-

^l&J ₀

~ 30

I-

_,

<(

20

10

OZONE

SCENARIO 1

27.-

0 ...

...r;_,_,_a.. ...

..._,._,_...,l..li--i. ...

-A ...

a. ....

.&...1

0 1

2

-3 -2 _,

CONCENTRATION CHANGE RELATIVE TO 1940

(10¹¹

cm-')

Figure 21 Change in the ozone concentration from its 1940 value, com- puted for scenario 1, as a function of altitude and for different years.

- ^I

""'

-

IIJ 0 :::>

... - ... _{_,}

◄

28.-

40.

30

OZONE

20 SCENARIO 1

10

o-_.... __________ ... __ ..._. ____ ... ______ _

-40 ^{-JO -20 -10}

⁰

RELATIVE CONCENTRATION CHANGE (•/.) (RELATIVE TO 1940)·

10

20

Figure 22 Same as figure 21, but the ozone change is expressed in re- lative values.

- -

~ Lt.I ,..,

_-

C) CD

z 2?

c:t 0 :c t-

u

Lt.I Lt.I

>~

.::

_{c:t _,} ~

rj ~

a: -

29.-

Q&--.--r--1---r-,,-,--,--,-.,....,-,._..._ ... _____ __

0.6

0.4

0.2

0

OZONE

TOTAL COLUMN

1990

2000 2010

TIME (Years)

2020 2030 2040

Figure 23 Future relative change in the total ozone amount as a function of time, computed in the 4 different cases.

30.-

the cases where all gases and only CFCs are considered is depicted in figure 24. The effect of a large aircraft emission can be estimated from figures 25 (scenario I) and 26 (scenario 2).

-

^~

-

I.LI C)

z

<Cl

u

J:

I.LI

>

....

<Cl

...J

I.LI

a:

1

0

-1

-2

-3

-4

1940

31.-

Cl••

C0₂ .N₂0 • CH₄

OZONE

TOTAL COLUMN

1960 1980 2000 2020 2040

TIME (Years)

Figure 24 Relative change in the total ozone concentration, as a function of time from 1940, computed in the 4 different scenarios and compared to the results of a similar calculation considering only the corresponding perturbations due to the emission of chlorocarbons.

32.-

2--- - ^•

.-

₁

-

^UJ _C)

z

et :I:

u

UJ

0

>

~ et

...J

UJ CFC only

0:: -1

I

OZONE(TOTAL COLUMN SCENARIO 1

-2--- ¹⁹⁴⁰

^{1960 1980}

²⁰⁰⁰ 2020 2040

TI ME (YEARS)

Figure 25 Relative change in the integrated ozone concentration, as a function of time from 1940 to 2040, obtained for scenario 1 and compared to (1) a case considering only the same chloro- carbons perturbation and to (2) a case where an injection of NO by aircraft engines is assumed in addition to the other

X

perturbations included in the scenario.

2 ----,....----,....----,....----,..--....--.,..---..---

l&I C)

z

◄ -l

:c u

l&I

~

-2

!c

..J

w a:

-3

CFC. • C0_{2 •} N₂0 +CH_{4 •} aircraft

'\_.

OZONE

TOTAL COLUMN SCENARIO 4

-4 - - - -

1940 1960 1980 2000 2020 2040

TIME (Years)

Figure 26 Same as figure 25 but for scenario 4.

33.-