Section 2.5

1. Anthropogenic Changes in Surface Albedo and the Surface Energy Budget Section 2.5 Narrated by: Erica Cherrelle Payne

2. 2.5.1 Introduction

3. 2.5.1 • Man-made changes to the land surface • Exerts RF • Changes in heat transfer • Changes in atmospheric momentum transfer • Large scale changes to surface albedo • Agricultural land vs. natural landscape • Snow and open land vs. forest • BC(black carbon) aerosols settling on snow

4. 2.5.1 • Land cover changes to surface properties • Surface emissivity • Flux of heat • Flux of air moisture • Aerodynamic roughness • Air temperature • Precipitation • Wind speed

5. 2.5.1 • Other influences on surface albedo and RF • Irrigation • Changes in vegetation cover • Changes in gases such as ozone and CO2 • Activities that do not affect RF • Heating buildings • Powering electrical appliances • Fuel combustion by vehicles • Heat release is not an RF

6. 2.5.2 Changes in Land Cover Since 1750

7. 2.5.2 • 1750 • 6-7% of land surface under cultivation • 1850 – 1950 • Rapid increase in cropland • Resulted in crop stabilization and decrease • Abandoned cropland allow forest regeneration

8. 2.5.2 • 1990 • Cropland covers 35-39% of global land • Forest cover decreased by 11 million km2 • Recent years • Land abandonment leads to reforestation • Rapid deforestation in tropics

9. 2.5.2 Current estimates of global land surface

10. 2.5.2 Change in cropland and pasture distribution during 1750 and 1990

11. 2.5.3 Radiative Forcing by Anthropogenic Surface Albedo Change Land Use

12. 2.5.3 • Uncertainties in creating RF data • Atlas-based data sets for present day vegetation • Recent data sets obtained by satellite • Data agreement on tall and short vegetation • Anthropogenic land cover change debate

13. 2.5.3 Differences in data sets

14. 2.5.3 • Uncertainties of mapping historical states • Most maps use a square grid system • Past vegetation assumptions • Large scale vs. local scale data sets

15. 2.5.4 Radiative Forcing by Anthropogenic Surface Albedo Change: Black Carbon in Snow and Ice

16. 2.5.4 • The presence of soot particles • Can decrease albedo of snow • Can affect snow melt • Uncertainties of BC effects • Internally or externally mixed • BC and snow particle size • Extended research • BC on snow and ice decreased surface albedo

17. 2.5.5 Other Effects of Anthropogenic Changes in Land Cover

18. 2.5.5 • Man-made climate modifications • Past tropical deforestation - +0.2°C • Warming more significant than albedo change • Radiative forcing effectiveness in the future

19. 2.5.6 Tropospheric Water Vapour from Anthropogenic Sources

20. 2.5.6 • Water usage • <1% from natural sources of vapour • 70% from irrigation • Impact of irrigation • Temperature • Humidity • Asia: Vapour increase of 1% in troposphere • Most impact from cooling

21. Section 2.6 Contrails and Aircraft- Induced Cloudiness

22. 2.6.1 Introduction

23. 2.6.1 • Supersonic and subsonic aircrafts • Subsonic aircrafts contribute to climate change • Contrails are left which mimic clouds • Flight path is through clear weather areas

24. 2.6.2 Radiative Forcing Estimates for Persistent Line-Shaped Contrails

25. 2.6.2 • Contrail effects • Create thin cirrus clouds • Reflect solar radiation • Trap longwave radiation • Increase of RF • Low understanding of contrails • Troposphere is not well known • Regional differences unknown

26. 2.6.3 Radiative Forcing Estimates for Aviation-Induced Cloudiness

27. 2.6.3 • Aviation aerosol • Contrails can shear and spread • Contrails mimic real clouds • Trends found only in USA • Contrail relevance • Too difficult to distinguish • Other gases are more influential