Gradual Climate Change or “Tipping Points” in
the System?
Carlos A Nobre
Chair, International Geosphere-Biosphere Programme (IGBP)
and National Institute for Space Research (INPE) of Brazil
Hotspots for GEC research: a
primary focus of IGBP research
1
The global conveyor belt
Surface Melt on Greenland happening
much faster than expected
Source: Roger Braithwaite, University of Manchester (UK)
70 meters thinning in 5 years
Increasing concern about ice-sheet stability
and a substantially larger rise in sea level
• Surface melting
For sustained warmings above 4.5±0.9 C in
Greenland (3.1±0.8 C in global average), it is
likely that the ice sheet would eventually
be eliminated. [Gregory and Huybrechts,
accepted]
• Dynamic instability
Satellite-era record melt of
2002 was exceeded in 2005.
Source: Waleed Abdalati, Goddard Space
Flight Center
2
Focus on Amazonia
Environmental Changes in Amazonia and the
Hypothesis of ‘Savannization’
Carlos A Nobre, Marcos Oyama, Manoel Cardoso,
Gilvan Sampaio, Luis Salazar, David Lapola, and Marcos Costa
“Climate Change and the Fate of the Amazon”
Oxford University, UK – 20-22 March 2007
Slide courtesy: IPAM
3
Does vegetation matter for the
Earth System ?
Is vegetation distribution a fingerprint of climate ?
or
Does vegetation distribution influence
and participate to climate (state and changes) ?
Does vegetation matter for
the Earth System ?
• The impacts of human activity on the Amazon rainforest could result in
the collapse of large portions of the rainforest and significant loss of
biodiversity within 30 to 50 years.
• A comparison is made with similar events in the Saharan ecosystem,
which was once a region of richer vegetation, before its abrupt collapse
about 6000 years ago
4
Remove vegetation from the continents
Î large changes will happen in the water cycle
Land=desert
Land=forest
ATMOSPHERE
421 000 km3
464 000 km3
71 000 km3
31 000 km3
410 000 km3
443 000 km3
137 000 km3
108 000 km3
OCEANS
37 000 km3
28 000
CONTINENTS
km3
Kleidon et al. (2000)
Vegetation partitions net radiation into more latent and less sensible heat
(figure taken from Kabat et al.: Vegetation, Water, Humans, and the Climate, IGBP BAHC)
5
The ecosystems of Amazonia are subjected to
a suite of environmental drivers of change
LUCC
Climate
Change
Fire
Climate
Extremes
The Hypothesis of ‘Savannization’
• Nobre et al. (1991) proposed that a post-deforestation
climate in Southern Amazonia would be warmer, drier
and with longer dry season, typical of the climate
envelope of the tropical savanna (Cerrado) domain of
Central South America.
• ‘Savannization’ in this context is a statement on regional
climate change and not intended to describe complex
ecological processes of vegetation replacement.
6
Biomes of tropical south America and
precipitation seasonality
Biomes of Brazil
Tropical Forest-Savanna
Boundary
Tropical Forest
Number of consecutive months
with less than 50 mm rainfall
Shrubland
Savanna
The importance of
rainfall seasonality
(short dry season) for
maintaining tropical
forests all over
Amazonia
Annual Rainfall
Sombroek 2001, Ambio
Cerrado s.s. SP
Floresta trop RO
Floresta trop Manaus
Floresta trop Santarém
Latent Heat flux (W m-2)
Savanna
Forest
Net Radiation (W m-2)
Source: Rocha (2004)
Forest
mm day-1
Evapotranspiration
seasonality in the
Amazon tropical
forest and savanna
Savanna
7
Is the current Climate-Biome
equilibrium in Amazonia the only
possible one?
Two Biome-Climate Equilibrium States found for South America!
-- current state (a)
-- second state (b)
Soil Moisture
Rainfall
anomalies
Oyama and Nobre, 2003
8
Precipitation mechanism in the Amazon
18 UTC
Unconditional probability of a wet day.
The daily data spans 1979 to 1993
1 mm < P < 5 mm
03 UTC
Annual Precipitation
In
sta
5 mm < P < 25 mm
Z
C
SA
bi
lit
yl
in
Sea Breezes
es
Source: Obregon, 2001
Ecological adaptation I: Deep rooting
Fraction of water ex
Dry season
tracted by roots
Wet season
Depth (m)
68%
84%
Water extraction at least up to 10 m
Source: Bruno et al., 2005 – Tropical forest data in Santarem km83
9
Ecological adaptation II: Hydraulic redistribution
b
a
Before rain
Daytime
Sap-flow velocity
b
Source: R. Oliveira
c
a
After rain
b
c
b
a
rain
c
+: water flow to the plant
-: water flow away from the plant
Source: Oliveira et al., 2005
Externally driven equilibrium
change
10
In 2006, total deforested area (clear-cutting) is
650,000 km2 in Brazilian Amazonia (17%)
Resilience
Stochastic Perturbations
Gradual Perturbations
affect Resilience
(e.g., deforestation,
fire,
Fragmentation, global
warming, etc.)
Does climate variability (severe droughts) play
the key role linking together climate change,
edaphic factors, and human use factors?
Source: Greenpeace/Daniel Beltra
I - LAND COVER
CHANGE
DEFORESTATION AND BURNING AROUND THE XINGU INDIGENOUS PARK, MATO GROSSO STATE, BRAZIL, 2004.
Source: Tropical deforestation and climate change / edited by Paulo Moutinho and Stephan
Schwartzman. -- IPAM - Instituto de Pesquisa Ambiental da Amazônia, 2005.
11
PROJECTED SCENARIOS
Control
60%
20%
40%
80%
100%
50%
or Soybean
Source: Soares-Filho et al., 2006 - Amazon Scenarios Project, LBA
Sampaio et al., 2007
Precipitation
PASTURE
SOYBEAN
Amazonia - SOYBEAN
Area: East/Northeast
Amazonia - PASTURE
Area: East/Northeast
1.2
1.1
1.0
DJF
MAM
0.9
JJA
0.8
SON
Relative Precipitation (p/p 0 )
Relative Precipitation (p/p 0)
1.2
1.1
1.0
DJF
0.9
MAM
JJA
0.8
SON
0.7
0.7
0.6
0.6
0%
20%
40%
60%
80%
100%
0%
20%
40%
60%
80%
100%
Deforestation Area (%)
Deforestation Area (%)
Precipitation Anomaly (%)
Season
All Pasture
All Soybean
JJA
-27.5%
-39.8%
SON
-28.1%
-39.9%
The reduction in precipitation is larger during the dry season, and is
more evident when the deforested area is larger than 40% !
Sampaio et al., 2007
12
II - FIRE
At long term, fires have also important effects on biomes
distribution:
less trees
Fires
more grasses
favor
savannas
in place
of forests
To account for fires when estimating the distribution
of the natural biomes, we developed a new long-term
fire parameterization based on the potential for
lightning during dry-wet season transitions
13
The new long-term natural fires parameterization is
based on major circulation patterns:
Long-term characteristics of the zonal wind
Average
Intra-annual variance
The potential for lightning/fires
in the tropics is higher were
combined long-term average
and intra-annual variance of the
zonal wind is lower than 3.5
m3/s3 (in grey):
↑ light./fire pot.
↓light./fire pot.
Cardoso et al. (2007), in review
Impact of using the new fire parameterization in the biome
estimates of the CPTEC Potential Vegetation Model:
Major vegetation types:
(1) broadleaf-evergreen trees (tropical
forest),
(2) broadleaf-deciduous trees
(temperate forest)
(3) broadleaf and needleleaf trees
(mixed forest)
(4) needleleaf-evergreen trees (boreal
forest)
(5) needleleaf-deciduous trees (larch),
(6) broadleaf trees with groundcover
(savanna)
(7) groundcover only (prairie, steppes)
(8) broadleaf shrubs with perennial
groundcover (caatinga)
(9) broadleaf shrubs with bare soil
(semi-desert)
(10) dwarf trees and shrubs with
groundcover (tundra)
(11) bare soil (desert)
(13) ice.
Accounting for fires corrected important differences between previous
model estimates and reference data for the position of natural savannas
in the tropics. In specific, large areas in India and SE Asia that were
initially estimated as savannas are now corrected to dry forests.
Cardoso et al. (2007), in review
14
Carvalho et al. (2001)
Land use
Dry season
At year-decade time scales, the
majority of fires in Amazonia
occur during the dry season as
a result of land use
Using remote-sensing fire data, we found new
statistical relations between precipitation and distance
to main roads, which are the major drivers for yearlydecade fire activity in the region:
Model
Data
Prob. fire
Satellite fire data
Precipitation
observations
t
To
.
ec
pr
al
x
de
in
Road maps
dex
ads in
in ro
a
m
.
Dist
Cardoso et al. (2003, 2007)
15
III - CLIMATE EXTREMES
The impact of droughts
Vegetation
vulnerability
to droughts
Percent attainment of the
Nix criteria [1983] for
savanna in the last 100
years
Climate conditions for tropical
savannas (Nix 1983)
Tmean > 24 C
13 C < Tcoldest month < 18 C
P(3 driest months) < 50 mm
P(6 wettest months) > 600 mm
1000 mm < Pannual < 1500 mm
(A) Observed drought frequency (% years); (B) distribution of savanna, transitional vegetation, and
forest across the legal Brazilian Amazon; (C) Land area (1000 km2) of vegetation types for pixels
with given drought frequency (%), forest land area is multiplied by 0.1 for scaling; (D) percent
attainment of the Nix [1983] criteria for savanna vegetation in the last 100 years.
Source: Hutyara et al, 2005
16
The Drought of Amazonia in 2005
Source: Dr. Virgílio Viana
Marengo et al. 2007
17
IV – GLOBAL WARMING
What are the likely biome changes
in Tropical South America due to
Global Warming scenarios of
climate change?
18
The impact of global climate change on tropical
forest biodiversity in Amazonia.
Climate Model: HADCM2GSa1
1% CO2 increase/yr
= SI/2
43% of 69 species of Angiosperms
become non-viable by 2095!
Source: Miles et al. 2004.
Climate Change Scenarios for Amazonia
Results from 15 AOGCMs for the SRES A2
and B1 emissions scenarios, prepared for
the IPCC/AR4.
Models: BCCR-BCM2.0, CCSM3, CGCM3.1(T47),
CNRM-CM3, CSIRO-MK3, ECHAM5, GFDL-CM2,
GFDL-CM2.1, GISS-ER, INM-CM3, IPSL-CM4,
MIROC3.2 (MEDRES), MRI-CGCM2.3.2,
UKMO-HADCM3, ECHO-G
19
Climate Change Consequences on the Biome distribution in
tropical South America
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.
Salazar et al., 2007
Climate Change Consequences on the Biome distribution in
tropical South America
2020-2029
SRES B1
SRES A2
2050-2059
2090-2099
SRES B1
SRES B1
SRES A2
SRES A2
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.
Salazar et al., 2007 GRL (accepted)
20
Climate Change Consequences on the Biome distribution in
tropical South America
Percentage of the area where more than 75% of the experiments for the A2 GHG scenarios, coincide as
projecting the permanence or disappearance of the current potential tropical forest, and where there is not a
conclusive consensus amongst models
Salazar et al., 2007 GRL (accepted)
CPTEC-INPE PVM 2
Current
pot veg
Vegetation distribution under
different CO2 concentration scenarios
250 ppmv
180 ppmv
140 ppmv
450 ppmv
600 ppmv
850 ppmv
Lapola, 2007 MSc Thesis at INPE
21
Projected distribution of natural biomes in South America for 2090-2099 from 14 AOGCMs
for the A2 emissions scenarios, calculated by the CPTEC-INPE PVM with Carbon Cycle
Lapola, 2007, MSc Thesis at INPE
Conclusions
The future of biome distribution in Amazonia in face
of land cover and climate changes
• Natural ecosystems in Amazonia have been under increasing
land use change pressure.
• Tropical deforestation, global warming, increased forest fires
and intense/more frequent droughts all act to reduce the
resilience of the tropical forest.
• The synergistic combination of regional climate changes
caused by both global warming and land cover change over
the next several decades, exacerbated by increased drought
and forest fire frequency, could tip the biome-climate state to
a new stable equilibrium with ‘savannization’ of parts of
Amazonia and catastrophic species losses.
22
The ethical dimensions of Global
Environmental Change
There is an issue of ethics and justice: the people
[and other forms of life] most likely to bear the
brunt of Global Environmental Change are those
who have contributed least to it
Historical contributions to CO2 emissions:
Europe
USA
China
Amazonia
30%
28%
8%
1% - 1.5%
THANK YOU!
23
CPTEC PVM 2
Current
pot veg
Vegetation distribution under
different annual mean temperature scenarios
-2°C
-4°C
-6°C
+2°C
+4°C
+6°C
Lapola et al., 2007
CPTEC PVM 2
Current
pot veg
Vegetation distribution under
different annual mean precipitation scenarios
(mm/day)
-0.2
-1.0
-3.0
+0.2
+1.0
+3.0
Lapola et al., 2007
24
Two Biome-Climate Equilibrium States found for
South America
Current potential vegetation
Forest
-- current state (a)
-- second state (b)
Savanna
Soil Moisture
Second State
Results of CPTEC-DBM Initial Conditions : desert
Rainfall
anomalies
Source: Oyama and Nobre, 2003
Precipitation – all Amazonia
Amazonia - SOYBEAN
1.2
1.1
1.1
1
DJF
0.9
MAM
JJA
0.8
SON
0.7
0.6
0.0%
20.0%
40.0%
50.0%
60.0%
80.0%
100.0%
R elative Precipitation
Relative Precipitation
Amazonia - PASTURE
1.2
1.0
DJF
0.9
MAM
JJA
0.8
SON
0.7
0.6
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
Deforestation Area (%)
Deforestation Area (%)
Precipitation Anomaly (%)
Season
All Pasture
All Soybean
JJA
-15.7%
-24.0%
JJAS
-13.7%
-22.0%
Sampaio et al., 2007
25
Is an equitable and sustainable
‘ecological footprint’ achievable?
6.0
metric tons of carbon per capita
5.0
Brazil
China
4.0
France
Germany
India
Indonesia
3.0
Japan
Russian Federation
2.0
United Kingdom
United States
Average per capita
Global CO2 emissions:
1980 Æ 0.93 t C
1999 Æ 1.04 t C
1.0
03
02
CDIAC, 2006
20
01
20
20
99
98
00
20
19
97
19
19
95
94
96
19
19
93
19
19
91
92
19
19
19
90
0.0
Per Capita Carbon Dioxide Emissions (1990-2003)
Amazonia - PASTURE
Amazonia - Pasture
Area: East/Northeast
Relative precipitation (p/p0)
1.05
1.00
member 1
0.95
member 2
0.90
member 3
member 4
0.85
member 5
0.80
average
y = -0.1451x 2 - 0.0577x + 1.0084
R2 = 0.9711
0.75
Polynom
(average)
0.70
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Deforested Area (%)
Sampaio et al., 2007
26
Amazonia - SOYBEAN
Amazonia - SOYBEAN
Area: East/Northeast
Relative Precipitation (p/p0)
1.05
1.00
0.95
member 1
member 2
0.90
member 3
member 4
0.85
member 5
0.80
average
2
y = -0.3149x + 0.0315x + 1.0102
R2 = 0.9771
0.75
Polynom
(average)
0.70
0%
20%
40%
60%
80%
100%
Deforested Area (% )
Sampaio et al., 2007
27