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

DEFORESTATIONDEFORESTATION

FIRESFIRES

AGRICULTUREAGRICULTURE

The ecosystems of Amazonia are subjected to a suite of environmental drivers of change

LUCC

FireClimateChange

ClimateExtremes

Summary of deforestation experiments in Amazonia since the late 1980´s.

• 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..

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

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

.

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

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

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

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

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?

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).

Interative CO2 and dynamic vegetation 2090s - 1990s

1850 2000 2100

Changes in Amazon forest coverage

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

• 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..