José A. Marengo Centro de Ciências do Sistema Terrestre - CCST Instituto Nacional de Pesquisas Espaciais - INPE “Tipping Points” do Sistema Climático e Riscos para o Brasil: Caso da Amazônia Simpósio: “Tipping Points” do Sistema Climático e Riscos para o Brasil. 5 Maio 2008 Rio de Janeiro, RJ

DEFORESTATION

FIRES

AGRICULTURE

The ecosystems of Amazonia are subjected to a suite of environmental drivers of change LUCC Fire Climate Change Climate Extremes

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 % 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 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) , (b) and (c) for B1 GHG emissions scenario and (d), (e) and (f) similarly for A2 GHG emissions scenario Salazar et al., 2007 GRL (accepted) Climate Change Consequences on the Biome distribution in tropical South America SRES B1 SRES A2

SeasonAll PastureAll Soybean JJA-27.5%-39.8% SON-28.1%-39.9% Precipitation 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

¾ of the CO 2 Brazilian emissions come from deforestation CO 2 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 carbon for the global land area (continuous lines) and South America alone (dashed lines).

Interative CO 2 and dynamic vegetation 2090s s Changes in Amazon forest coverage

Coupled climate—vegetation models project dramatically different futures (CO 2, vegetation, T) using different ecosystem models from different models.  CO 2 => 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..