Deforestation and Climate ChangePresented by: Audrey Eggenberger
Geography: ASCS major
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
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
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
Focus: Forests
Tropical
Boreal
Temperate
BorealTemperat
e
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
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
Climatological Implications Warming influence
from: Addition of CO2
greenhouse gas Decreased
evapotranspiration (short run)
Cooling influence from: Increased surface
albedo Decreased
evapotranspiration (long run)
Greenhouse Effect
Albedo Effect
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
Amazon Deforestation and Climate ChangeShukla et. all
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
Area of interest
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
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
Results cont. Reduction in
evapotrans-piration by 49.6 cm annually
Reduction in precipitation by 64.2 cm annually
Deforestation case
Control case
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
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
Experiment
6 different model runs (from year 2000-2150):1. Control—no CO2 or deforestation2. Standard—no deforestation3. Tropical—deforestation in tropics only4. Temperate—deforestation in mid-latitudes 5. Boreal—deforestation in boreal zones6. Global—deforestation EVERYWHERE
Results In Global Case
(compared to Standard): Atmospheric CO2
content higher More ocean uptake
of CO2 Annual mean
temperature COOLER (by ~0.3K)
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
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.
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.
Boreal Zone Large albedo increase
+ already high albedo (snow) = MUCH more reflected SWdn
Raised CO2 levels 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.
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.
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.
Conclusions/Opinions Afforestation in tropics = beneficial Afforestation in temperate and boreal zones
= counter productive Complex atmosphere-biosphere dynamic
Teleconnection and 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
Any Questions??