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??