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José A. Marengo Centro de Ciências do Sistema Terrestre - CCSTInstituto Nacional de Pesquisas Espaciais - INPE
“Tipping Points” doSistema Climático e Riscos para o Brasil:
Caso da Amazônia
Simpósio: “Tipping Points” do Sistema Climático e Riscos para o Brasil.
5 Maio 2008Rio de Janeiro, RJ
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DEFORESTATIONDEFORESTATION
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FIRESFIRES
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AGRICULTUREAGRICULTURE
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The ecosystems of Amazonia are subjected to a suite of environmental drivers of change
LUCC
FireClimateChange
ClimateExtremes
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Summary of deforestation experiments in Amazonia since the late 1980´s.
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• In a complex system, "tipping point" represents a level, and if as a consequence of an imposed forcing this level is overpassed, the system may suffer an abrupt change.
• In the case of the Amazon forest, if warming due to increase in concentrations og GHG (either natural or anthropogenic) is above 3,5 a 4 C, there is a risk of a "tipping point" leading to savannization.
• A recent study by Sampaio (2008) identified another “tipping point”, when the deforested area reached 40-50% level, leading also to savannization
• Caution: this is a concept used in climate modeling, and should consider model uncertainties
On tipping points..
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Need to advance our understanding of critical tipping-points and hot-spot systems at risk, such as the Amazon.
• The picture remains relatively scanty, with limited system-wide mapping of thresholds, cross-scale interactions and how system components reinforce each other amplifying the risk of crossing thresholds.
Tipping Points of the Climate System(GHG gases concentration?, deforestation?)
Externally driven equilibrium change
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Multiple Equilibria, Persistence & Climate
How does a system get to one or the other? Controlled by: changes in extreme events, in concert with shifts in the mean.
A shift in climate, due to natural or anthropogenic causes, can change the frequency and magnitude of disturbance. The change in relative system stability might make a vegetation change irreversible (e.g. Cox et al, 2001 and Oyama & Nobre 2004), but it might take a disturbance for the shift to occur. Leads to the concept of instability
.
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Question 1: Is there a “tipping point” of deforestation to induce abrupt changes to the new biome-climate
stable equilibrium?
Natural vegetation-Present Natural vegetation-2100
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Projected distribution of natural biomes in South America for 2090-2099 from 15 AOGCMs for the A2 emissions scenarios, calculated by using CPTEC-INPE PVM.
Climate Change Consequences on the Biome distribution in tropical South America-Simulation of deforestation (model deforestation)
Salazar et al., 2007
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Grid points where more than 75% of the models used (> 11 models) coincide as projecting the future condition of the tropical forest and the savanna in relation with the current potential vegetation. The figure also shows the grid points where a consensus amongst the models of the future condition of the tropical forest was not found. for the periods (a) 2020-2029, (b) 2050-2059 and (c) 2090-2099 for B1 GHG emissions scenario and (d), (e) and (f) similarly for A2 GHG emissions scenario.
2050-2059 2090-20992020-2029
Salazar et al., 2007 GRL (accepted)
Climate Change Consequences on the Biome distribution in tropical South America
SRES B1 SRES B1 SRES B1
SRES A2 SRES A2 SRES A2
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Season All Pasture All Soybean
JJA -27.5% -39.8%
SON -28.1% -39.9%
PrecipitationAmazonia - PASTUREArea: East/Northeast
0.6
0.7
0.8
0.9
1.0
1.1
1.2
0% 20% 40% 60% 80% 100%
Deforestation Area (%)
Rel
ativ
e P
reci
pit
atio
n (
p/p
0)
DJF
MAM
JJA
SON
Amazonia - SOYBEANArea: East/Northeast
0.6
0.7
0.8
0.9
1.0
1.1
1.2
0% 20% 40% 60% 80% 100%
Deforestation Area (%)
Rel
ativ
e P
reci
pit
atio
n (
p/p
0)
DJF
MAM
JJA
SON
PASTURE SOYBEAN
Precipitation Anomaly (%)
Sampaio et al., 2007
The reduction in precipitation is larger during the dry season, and is more evident when the deforested area is larger than 40% !
Human made deforestation
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Emissão brasileira de CO2 em 1994 por setor
23%
3%
0%
74%
0%
Energia Processos IndustriaisAgropecuária Desmatamento e queimadasTratamento de resíduos
v
¾ of the CO2 Brazilian emissions come from deforestation
CO2 Brazilian emissions (per capita):• 0,5 ton C/year of fossil origin• 1,5 ton C/year from mean deforestation• 1,0 ton C/year from deforestation in 2007
Question 2: Is there a “tipping point” of increase in GHG concentration and subsequent warming to the new biome-
climate stable equilibrium?
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Effect of climate/carbon-cycle feedbacks on CO2 increase and global warming (Cox et al 2000).
global-mean and land-mean temperature,Global-mean CO2 concentration,
Model with dynamic vegetation and interative CO2
Soil carbonfor the global landarea (continuous lines) and South America alone (dashed lines).
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Interative CO2 and dynamic vegetation 2090s - 1990s
1850 2000 2100
Changes in Amazon forest coverage
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Carbon Flux: Ocean to Air
-10-8-6-4-202468
10
1850 1900 1950 2000 2050 2100
Pg
C/y
rCox et al (2000)
Friedlingstein et al (2001)
Carbon Flux: Land to Air
-10-8-6-4-202468
10
1850 1900 1950 2000 2050 2100
Pg
C/y
r
Atmospheric CO2
200300400500600700800900
1000
1850 1900 1950 2000 2050 2100
pp
m
Global Mean Temperature
13
14
15
16
17
18
19
20
1850 1900 1950 2000 2050 2100
Ce
lsiu
s
Coupled climate—vegetation models project dramatically different futures (CO2, vegetation, T) using different ecosystem models from different models.
CO2 => 700 => 500
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• In a complex system, "tipping point" represents a level, and if as a consequence of an imposed forcing (natural or anthropogenic) this level is overpassed, the system may suffer an abrupt change.
• In the case of the Amazon forest, if human made deforestation reaches 40% or more, savannization may occur
• If CO2 reached about 700 ppm leading to a global warming of about 3.5 C
• Caution: this is a concept used in climate modeling, and should consider model uncertainties, and may vary between models (ex. HadCM3 of the UK and IPSL from France)
On tipping points..