Vulnerability of Primary Production to Climate Extremes Lessons from the 2003 heatwave in Europe Ph. Ciais, M. Reichstein, N. Viovy A. Granier, J. Ogée, V. Allard, M. Aubinet, Chr. Bernhofer, A. Carrara, F. Chevallier, N. De Noblet, A. Friend, T. Grünwald, B. Heinesch, P. Keronen, A. Knohl, D. Loustau, G. Manca, G. Matteucci, F. Miglietta, J.M. Ourcival, K. Pilegaard, S. Rambal, G. Seufert, J.-F. Soussana, M.-J. Sanz, E.D. Schulze, T. Vesala, and R. Valentini
Interannual variations in CO 2 growth rate
Linking with bottom up observations The 2003 European heatwave
Will the greening continue with more frequent climate extremes? % per year Nemani et al., Science 2003 Secular increase in primary productivity from satellite NDVI over the past years
Coupled Climate-Carbon models Predict an Increase in NPP and in carbon storage in Temperate Regions Tropical soil drying Longer growing seasons Berthelot et al., GBC 2003 See also Cox et al., Nature 2001
Precipitation history in Bavaria Historical temperature records in Switzerland Summer temperature reconstruction from harvest dates in Burgundy Shär et al., Nature 2003 Chuine et al., Nature, 2003
Temperate and Mediterranean forests
2003 modelling system Tower Tower Climate Climate hourly 2003-2003 hourly hourly space time ORCHIDEE model Tower fluxes Measured NEE, ET Derived GPP, NPP Grid point Global Climate 1900-2003 Hourly 30-100 km Model LAI Model FAPAR Model GPP, TER Model ET Model NPP Spatial average EOS-MODIS Crop Yield FAPAR Spatial average Country Average / species
Global biospheric model ORCHIDEE meteorological forcing rain, température, humidity, incoming radiation, wind, CO2 SECHIBA energy & water cycle photosynthesis output variables sensible & latent heat fluxes, CO2 flux, net radiation ORCHIDEE Dt = hour LAI, roughness, albedo STOMATE vegetation & soil carbon cycle phénologie, allocation, Dt = day soil water, surface temperature, GPP NPP, biomass, litterfall vegetation types LPJ spatial distribution of vegetation competition, fire, Dt = year prescribed vegetation
Comparing gross and net fluxes during summer 2002 and 2003
Abnormal Climate and Productivity in 2003 Model verification with EOS- MODIS FAPAR
Verification against crops yield national data
2003 is the largest productivity crash of the past 100 years -%
How abnormal is 2003? 0.80 avg fapar Jul-Sep 0.75 0.70 0.65 GIMMS MODIS GIMMS avg ± 5 standard deviations MODIS avg ± 5 standard deviations 0.60 1980 1985 1990 1995 2000 2005 Year
Independent inversion estimate Inversion / stations / interannual winds / resolved on each model grid point Peylin et al. In prep
Uniquely dense eddy covariance network to map climate-carbon-water interactions at the regional level Severe drop of transpiration and GPP Respiration tailed off with the GPP drop rather than increasing with temperature ; forests became net CO2 sources to the atmosphere in summer! Anomalous source of 0.5 PgC y -1, undoing years of mean sink, enough to explain 50% of the global CO2 growth rate anomaly
Processes Soil water content variation model and observations indicate large water stress at all sites in 2003 with Root Extractable Water REW < 0. 200 Vielsalm extractable water (mm) 150 100 50 0 0 60 120 180 240 300 360 DOY (2003) Hyytiala Hainich Hesse SorØ Tharandt Braschaat Fougères Bray Lille Grillenburg Loobos Breda et al.
water-stress controls on stomatal conductance Hesse daily canopy conductance gc* (cm s -1 ) 1.0 0.8 0.6 0.4 gc* REW 1.0 0.8 0.6 0.4 REW 0.2 0.2 0.0 0.0 100 150 200 250 300 1,0 DOY (2003) 0,8 gc (cm s-1) 0,6 0,4 gc_2002 gc_2003 0,2 Granier et al. submitted 0,0 150 180 210 240 270 300 DOY
Response of ecosystem fluxes to high temperatures and precipitation deficits
No Changes in water use efficiency 8 7 6 400 5 GPP [ gc m -2 month -1 ] 300 200 100 Ha02 Th02 So02 Vi02 So03 Ha03 He03 Th03 Vi03 He02 Sa02 Ro02 Ca02 Ca03 Hy03 Hy02 Br02 Sa03 Ro03 Br03 4 3 2 1 Pi03 Pi02 0 0 20 40 60 80 Evapotranspiration [mm month -1 ]
Unprecedented decrease in NPP during the past century No intrinsic change in water use efficiency Delayed impact on carbon balance may be extended over several years via mortality, insect attacks, tree damage
Vulnerability of carbon stocks to climate extremes
Take home In the future, adverse impacts of climate extremes may cancel out any benefits of moderate climate change European temperate productivity may be durably reduced if extremes become more frequents In the long run, conifer forest may be more adapted to European future climate conditions
Heat Drought Atmospheric water stress + Transpiration + +/- + - Soil water limitations + + +0. GtCy - anomaly NEE - TER - -0% - Stomatal closure GPP -0%
Independent tree ring verification!c (mm) 25 20 15 10 Hesse: seasonal variation of tree circumference as measured on 11 beech trees among the dominant and codominant crown classes during the period 1999-2003 (the same trees were measured each year). 1999 2000 2001 2002 2003 5 0 60 120 180 240 300 DOY A. Granier pers. Comm
GPP modelled vs measured anomaly