SCIAMACHY book. Ozone Recovery? Michel Van Roozendael, BIRA- IASB. ATC14, October, Jülich, Germany

Transcription

1 SCIAMACHY book Ozone Recovery? Michel Van Roozendael, BIRA- IASB ATC14, October, Jülich, Germany

2 1928: start of CFC production 1971: 1 st observation of CFC in the atmosphere (J. Lovelock) 1974: identification of O 3 destruction potential by CFC: Rowland & Molina 1995: Nobel prize in chemistry: F. Rowland, M. Molina & P. Crutzen, : 80% of stratospheric chlorine is of anthropogenic origin 2

3 Long term ozone depleeon Increasing anthropogenic emissions, since industrial revolueon, esp. CFCs since 1960 Ä increasing concentraeons of destruceve radicals Ä steady decrease of O 3 on a global scale Recurrent spring- Eme ozone hole at the South pole Seasonal ozone depleeon in the North pole, strongly modulated by dynamics 3

4 Nature, Vol. 315, 16 May 1985 First alarming signs of O 3 degradaeon were given in 1982 and 1985 based on Dobson measurements at Syowa and Halley Bay (since 1957) Ozone layer thins dramaecally in the local spring down to ~ 100 DU This phenomenon was not expected! 4

5 Evolution of average (monthly) O 3 layer thickness between 1956 and 1986 in October In Februari 5

6 Heterogeneous chemistry on PSCs 6

7 Experimental evidence Ozone and reaceve chlorine measurements from a flight through the ozone hole in AntarcEca, 1987 Ozone (Scale at Left) 1.5 Ozone Abundance (Parts per Billion) Reactive Chlorine Abundance (Parts per Billion) Reactive Chlorine (Scale at Right) Latitude (Degrees South) Antarctic Polar Air

8 Success of Montreal protocol Used in Aerosols, Refrigeration, Air Conditioning and Manufacturing of Foams. 8

9 Effect of Montreal Protocol Max en 1997 Reduction of chlorine and bromine in the stratosphere follows decrease of concentrations of the surface with a delay of 3 to 5 years = time to reach from troposphere stratosphere. BrO above Norway (60 N) Max en 2001 Courtesy: Univ. Liège Courtesy: F. Hendrick, IASB 9

10 Success of the Montreal Protocol The impact of the Montreal Protocol on climate is of order 5-6 >mes larger than the objec>ves of the Kyoto Protocol ! Reduc>on by Montreal Protocol of ~12 GtCO 2 - eq/yr 10

11 Monitoring of the ozone hole using satellites and models 11

12 EvoluEon of the Spring polar ozone over the North Pole from 1979 unel 2011 MACC/MSR, KNMI 12

13 13

14 What would have happened to the ozone layer if chlorofluorocarbons (CFCs) had not been regulated? Newman et al., ACP,

15 O 3 in the middle laetude: Current situaeon 6% (3.5%) lower than average in SH (NH) UV has not increased since the late 1990s O 3 hole at the poles is sell as in early 1990 (subject variability) i.e. in AntarcEca in October, 40% lower than in 1980 UV on AntarcEc is higher by 55 to 85% than in Evidences for changes in SH tropospheric summereme circulaeon due to AntarcEc ozone hole The stratosphere has cooled a few K between 1980 and 1995 due to ozone depleeon; the cooling reinforced by increasing GHG esp. in recent years 15

16 Coupling between ozone and climate ConcentraEons of greenhouse gases (CO 2, CH 4, N 2 O,...) rise T rises at the surface; but decreases in the stratosphere Atmospheric transport changes, rate of chemical reaceons changes Frequency of formaeon of clouds, aerosols and PSC change RadiaEon balance changes Ozone formaeon / degradaeon is influenced, in turn ozone affects UV, T stratosphere... 16

17 Future evolueon of ODS EESC back to 1980 levels: Ø in ~2050 Ø in ~2065 at the poles (older air) 17

18 Future evolueon of mid- laetude ozone WMO Average total column ozone changes over the same period, from muleple model simulaeons compared with observaeons between 1965 and Four possible greenhouse gas (CO 2, CH 4, and N 2 O) futures are shown. The four scenarios correspond to +2.6 (purple), +4.5 (green), +6.0 (brown), and +8.5 (red) W m - 2 of global radiaeve forcing 18

19 Impact of projected changes in GHGs on ozone Increased CO 2, CH 4 and N 2 O cools the stratosphere, which tends to increase O 3 because of temperature- dependent chemistry (reduced efficiency of loss) Increased CH 4 and N 2 O also have further chemical impact on O 3 CH 4 increases O 3 by miegaeng the effect of halogen- driven O 3 destruceon catalyec cycles N 2 O decreases O 3 through enhancing the efficiency of the NOx- driven catalyec cycles 19

20 Evidence for O 3 recovery in upper stratosphere O 3 recovery at 45 km aletude is due to combinaeon of reduceon in ODS (Montreal protocol) reinforced by cooling due to GHG increase 20

21 Predicted reduction of the tropical ozone layer Recent evidence for changes in tropical upwelling and higher laetudes downwelling due to climate change à Impact on ozone distribueon 21

22 Summary O 3 on a global scale will return to state from 1980 by 2050, i.e. faster than ODS, namely: Around in middle laetudes of both hemispheres Around in AntarcEca The increase of ozone will be accelerated in a colder stratosphere under the impact of GHGs As result, at the end of the 21 st century the stratospheric ozone concentraeon will be higher than in 1980 Tropical ozone is expected to decrease due to climate- change induced changes in the Dobson- Brewer circulaeon The climate benefits of the Montreal Protocol could be significantly offset by projected emissions of HFCs used to replace ODSs Large uncertainees in future emission scenarios and resuleng impacts 22

23 There are links between the stratospheric ozone evolution and climate change, and air pollution and atmospheric transport, and... These effects make the scientific questions much more complicated, and make it very difficult to design the 23