Changes in Atmospheric Constituents and in Radiative Forcing Part I

1. Changes in AtmosphericConstituentsand in RadiativeForcingPart I Stautzebach Elena

2. Summary • Introduction: - Whatisradiativeforcing? - Whyisradiativeforcing relevant forclimatechange? • Part 1: AnthropogenicGreenhouse Gases- AtmosphericCarbon Dioxide- AtmosphericMethane- Other Kyoto Protocol Gases- Montreal Protocol Gases- Ozone- StratosphericWaterVapour • Part 2: Aerosols- Directradiativeeffects- Indirecteffects (Cloud Albedo Effect)

3. WhatisRadiativeForcing? ΔTs = λ ∙ RF

4. Components oftheClimate Change Process

5. Part 1 AnthropogenicGreenhouse Gases

6. Most importantgreenhousegases • Carbon dioxide (CO2) • Methane (CH4) • Other Kyoto Protocol Gases: N2O; PFCs; HFCs; SF6 • Montreal Protocol Gases: CFCs; HCFCs… • Ozone • Stratospheric water vapour

7. Carbon dioxide (CO2)Sources • use of fossil fuel in transportation • building heating and cooling • manufacture of cement • Deforestation

8. Carbon dioxide (CO2) • RadiativeForcing calculations:- CO2reference level- recent changes in atmospheric mixing ratios • Different methods for CO2–measurements:- In situ continuous measurements - Air sample flask programs- Isotope ratio mass spectrometry- Atmospheric O2 measurements

9. In situ continuous measurements Continuous measurements at Mauna Loa, Hawaii since 1958

10. Air sample flask programs • to supplement in situ measurement • to estimate sources and sinks • National Oceanic and Atmospheric Administration’s Global Monitoring Division in the USA • Isotope ratio mass spectrometry • Measuresespecially CO2emissionsfrom fossil fuelcombustion

11. Atmospheric O2 measurements Atmospheric O2 and CO2 changes are inversely coupled during plant respiration and photosynthesis

12. Results • Increase of 100 ppmover the last 250 years • CO2 emissions due to fossil fuel combustion and cement manufacture have increased by 70% over the last 30 years • radiative forcing is estimated of 1,66 ± 0,17 W/m² • ¾ of the current radiative forcing is due to fossil fuel and cement production

13. Methane (CH4)Sources • wetlands • rice agriculture • biomass burning • emissions from living vegetation • fossil fuel mining  Sources are well known but the strength of each source component is not

14. MethaneHistorical evolution • In the last 650 kyr: - lows of about 400ppb during glacial periods - - highs of about 700ppb during interglacial periods (770 ppb at Vostok) • Between 1700 and 1800: global value of 714 ± 4ppb

15. Methane (CH4) • Increaseofabout 30% in the last 25 years • growth rate has decreased substantially • growth rate shows large anomalies

16. Results • In 2005 CH4 mixing ratio is at 1774ppb • RadiativeForcing of +0,48 ±0,05 W/m²  CH4is the second highest radiative forcing after CO2

17. Other Kyoto Protocol Gases N2O • rapid rise in the last 200 years • Since 1998 N2O levels have risen to 319 ± 0,12ppb in 2005 • radiative forcing of +0,16 ± 0,02 W/m²

18. Other Kyoto Protocol Gases • PFCs • HFCs • SF6 • very effective absorbers of infrared radiation  even small amounts contribute significantly to the radiative forcing of the climate system

19. Montreal Protocol Gases = international treaty on substances that deplete the ozone layer • CFCs, HCFCs, chlorocarbons, bromocarbons, halons • Since Montreal Protocol decrease of CFC-11 and CFC-113, stagnation of CFC-12

20. Ozone StratosphericOzone • Ozone hole overAntarctica • NH: 30% of the ozone trends are related to dynamical effects • temporally and seasonally changes • total stratospheric ozone RF is -0,05 ± 0,10 W/m² since pre-industrial time Tropospheric Ozone • regional differences:- decrease in industrialized regions - Increase in developing countries • RF increased by 0,35W/m² since pre-industrial time

21. Stratospheric Water Vapour • long-term increase • Forcing mechanisms:- volcanic eruptions- biomass burning aerosol- changes in CH4 oxidation rates - injection of water vapour by aircraft • Mechanisms not linked to an external forcing agent: - changes in tropopause temperatures or circulation  RF: +0,07 ± 0,05 W/m².

22. Part 2 Aerosols

23. Aerosols DirectEffects Indirecteffects mechanism by which aersols modify the microphysical and radiativeproperties of clouds Cloud albedo effect Cloud lifetime effect mechanism by which aerosols scatter and absorb shortwave and longwaveradiation Semi-directEffects • heating of the troposphere • and therefore influences cloud • formation and lifetime

24. Seasonal variabilityofthe aerosoloptical depth

25. DirectEffects

26. Directradiativeeffect

27. RadiativeForcingforCombined Total Aerosol • Sulphate Aerosol: -0,4 ± 0,2 W/m² • OrganicCarbon Aerosol from Fossil Fuels: -0,05 ± 0,05 W/m² • Black Carbon Aerosol from Fossil Fuels: +0,2 ± 0,15 W/m² • BiomassBurning Aerosol: +0,03 ± 0,12 W/m² • Nitrate Aerosol: -0,1 ± 0,1 W/m² • Mineral Dust Aerosol: -0,1 ± 0,2 W/m²  CombinedaerosoldirectRadiativeForcing:-0,5 ± 0,4 W/m²

28. Indirecteffect

29. IndirectRadiativeForcingLink between Aerosol particles and cloud microphysics • Nonlinearrelationsshipbetweenaerosolsandclouddropletnumberconcentrations:Nd = Nab • Aerosols mostlyconsistofinternalmixture • Size oftheparticleismoreimportantthanthecomposition • Radiation transfer in coldcloudsdepending on insoluble particleswithintheicecrystals

30. RadiativeForcingfromCloud Albedo Effect • RF estimation: -0,7 W/m² asthe median, with a 5 to 95% rangeof -0,3 to -1,8 W/m² • Increase in theknowledgeoftheaerosol-cloudinteractionssincethe TAR result  Elevation ofthelevelofscientificunderstandingtolow

31. Part 3 Conclusion

33. Thankyouforyourattention!