Deforestation and Climate Change

1. DeforestationandClimateChange Amazon Deforestation and Climate Change (1990) By: J. Shukla et. all Combined Climate and Carbon-Cycle Effects of Large-Scale Deforestation (2007) By: G. Bala et. all Presented by: Audrey Eggenberger Geography: ASCS major

2. Profile of the Amazon • Incredible biodiversity • Important ozone sink • Important role in global tropospheric chemistry • Experiencing alarming rates of deforestation • If nothing is changed, Amazon will disappear in 50-100 years

3. What do plants do? • Absorb and store CO2 • Act as H2O reservoir and heat reservoir • Transpiration • Reflect incoming solar radiation (SWdn) • Albedo—fraction of SWdn reflected

4. Focus: Forests Boreal Boreal Temperate Temperate Tropical

5. Vegetation and Climate • Traditionally vegetation type was thought to be a RESULT of local climate • Complex experiments have shown, however, that the type of vegetation can influence regional climate • Current climate and vegetation coexist in a dynamic equilibrium

6. Effects of Deforestation • Releases CO2 stored in the living plants to atmosphere and eliminates future storage • Alters physical properties of Earth’s surface • Root system • Water and heat storage • Albedo

7. Climatological Implications • Warming influence from: • Addition of CO2 greenhouse gas • Decreased evapotranspiration (short run) • Cooling influence from: • Increased surface albedo • Decreased evapotranspiration (long run) Albedo Effect Greenhouse Effect

8. It’s Complicated… • Dynamic equilibrium • Complex interactions • Teleconnection and Feedback problem • Models are unable to solve this problem in foreseeable future • There are local variations too • Subgrid-Scale Problem

9. Amazon Deforestation and Climate ChangeShukla et. all Area of interest • Investigates the effects of deforestation on the local physical climate system • Uses a coupled numerical model of global atmosphere and biosphere • Control Case: forest intact • Deforestation Case: forest cover is replaced by degraded pasture

10. Experiment • Coupled model was integrated for 1 year for both the Control and Deforestation cases • Only change from Control to Deforestation case was the replacement of forest with pasture (grass) • Integrations were carried out for 12.5 months, starting from December 15th

11. Results • Surface/soil temp (Ts) warmer • Consistent with reduction in evapotranspiration (E) • More Lwup (Ln) • Higher albedo (a), leads to reduction of absorbed SWdn • Reduced moisture and heat storage capacity Recall: B=SH/LH

12. Results cont. • Reduction in evapotrans-piration by 49.6 cm annually • Reduction in precipitation by 64.2 cm annually Control case Deforestation case

13. Bottom Line… • Rise in surface temperature locally • Significant decrease in precipitation • Precip decrease is larger than the reduction in evapotranspiration • Moisture flux decreases as a whole • Longer dry season • Makes reclamation by rainforest highly unlikely • Valuable ecosystem disrupted, if not devastated

14. Combined Climate and Carbon-Cycle Effects of Large-Scale DeforestationBala et. all • Investigates global effects of deforestation on climate • Uses 3-D coupled global carbon-cycle and climate model • Lawrence Livermore National Lab Integrated Climate and Carbon (INCCA) Model • Vegetation, land, ocean

15. Experiment • 6 different model runs (from year 2000-2150): • Control—no CO2 or deforestation • Standard—no deforestation • Tropical—deforestation in tropics only • Temperate—deforestation in mid-latitudes • Boreal—deforestation in boreal zones • Global—deforestation EVERYWHERE

16. Results • In Global Case (compared to Standard): • Atmospheric CO2 content higher • More ocean uptake of CO2 • Annual mean temperature COOLER (by ~0.3K)

17. Cooling? Wait…what?! • It’s all thanks to our good friend, albedo • Albedo increases for all forest domains • More SWdn reflected globally • Decrease in evapotranspiration also helps • Smaller Heat reservoir

18. A Closer Look: Tropics (Includes SH mid-latitudes) • Raised albedo = more reflected SWdn • Less moisture= fewer clouds, greater sunlight penetration • Raised CO2 levels = warming • RESULT: Slight cooling(~0.3K) Simulated spatial temperature difference relative to Standard case centered on year 2100 for tropical deforestation.

19. Temperate Zone • Raised albedo = more reflected SWdn • Raised CO2 levels = warming • Clouds are not important factor • RESULT: Cooling (~1.6K) Simulated spatial temperature difference relative to Standard case centered on year 2100 for temperate zone deforestation.

20. Boreal Zone • Large albedo increase + already high albedo (snow) = MUCH more reflected SWdn • Raised CO2levels and sensitivity = warming • Clouds are not important factor • RESULT: Cooling (~2.1K, some places exceed 6K) Simulated spatial temperature difference relative to Standard case centered on year 2100 for boreal zone deforestation.

21. Global Case • Adding the three zones together is equivalent to the Global Case • As stated earlier, net result globally is COOLING by about ~0.3K Simulated spatial temperature difference relative to Standard case centered on year 2100 for global deforestation.

22. In Summary… • Although removal of forests causes global warming through Carbon-Cycle effects, this warming is overwhelmed by the local and global cooling effects of increased albedo and decreased evapotranspiration, most strongly in the boreal regions.

23. Conclusions/Opinions • Afforestation in tropics = beneficial • Afforestation in temperate and boreal zones = counter productive • Complex atmosphere-biosphere dynamic • Teleconnectionand Feedback Problem • Results vary by location • Subgrid-Scale Problem • Problems with INCCA Model • Comparable studies with other models needed • Goal should still be preservation of ecosystems

24. Any Questions??