Eggenberger

Report
Presented 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 50100 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
Boreal
Temperate
Tropical
Boreal
Temperate
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
from:


Addition of CO2
greenhouse gas
Decreased
evapotranspiration
(short run)
 Cooling
from:


influence
Albedo
Effect
influence
Increased surface
albedo
Decreased
evapotranspiration
(long run)
Greenhouse
Effect
It’s Complicated…
 Dynamic
equilibrium
 Complex interactions


Teleconnection and
Feedback problem
Models are unable to solve
this problem in foreseeable
future
 There
too

are local variations
Subgrid-Scale Problem
Amazon Deforestation and
Climate Change
Shukla 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
Control case
Deforestation case
in
evapotranspiration by
49.6 cm
annually
 Reduction in
precipitation
by 64.2 cm
annually
Bottom Line…


Rise in surface temperature locally
Significant decrease in precipitation

Precip decrease is larger than the reduction in
evapotranspiration


Longer dry season


Moisture flux decreases as a whole
Makes reclamation by rainforest highly unlikely
Valuable ecosystem disrupted, if not
devastated
Combined Climate and
Carbon-Cycle Effects of LargeScale Deforestation
Bala 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
1.
2.
3.
4.
5.
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
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
Simulated spatial
temperature difference
relative to Standard
case centered on year
2100 for boreal zone
deforestation.
 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)
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??

similar documents