BGC Working Group Meeting 28-30 March 2006 Effects of land cover change: Preliminary results from a hierarchy of models G Bala, M E Wickett, T J Phillips, D.Lobell, S. Gibbard Energy and Environment Directorate Lawrence Livermore National Laboratory Livermore, CA 94550 USA Ken Caldeira Carnegie Institution Department of Global Ecology Stanford, CA 94305 USA Christine Delire Universite Montpellier, France

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Gallatin National Forest – Montana, US.

Carbonfund is supporting the planting of pine, spruce and other indigenous conifers suitable to the region. These trees are being planted in areas damaged by recent forest fires that won't regenerate on their own.

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CO2 Offset: 500 tons

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Ozark National Forest – Arkansas, US.

Carbonfund is supporting tree plantings of primarily red oak trees in areas of the forest that have been damaged by the red oak borer.

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CO2 Offset: 500 tons

Land-use change and climate

• Studies focusing on boreal forests • Studies focusing on historical changes

Temperature change ( °C) from conversion from natural to actual vegetation

What are the climatic effects of afforestation?

Cooling due to carbon storage Warming due to albedo change Cooling due to evaporation Increase in roughness length (climate effect unknown)

Forest regrowth may store carbon, but warm the world

Regrowing forests store carbon [cooling effect] but the dark forest canopy absorbs more sunlight [warming effect] Net effect is warming [in this calculation]

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0 Albedo effect Net effect Carbon dioxide effect 100 200 Year 300 400 500

This study (Thought Experiments)

• NCAR CLM - Offline simulations with one PFT at a time • NCAR CAM3 with slab ocean – Tree world and grass world • LLNL Climate Carbon Model (INCCA) – Global deforestation (Grass world)

Effect of local vegetation change

CLM offline simulation

Effect of global vegetation change

CAM3-SOM simulation

Direct climate effect of global afforestation

INCCA – INtegrated Climate CArbon Sun Climate Change CO 2 Atmosphere (NCAR CCM) Ocean (POP) Marine Bio-geochemistry (OCMIP) Terrestrial Ecosystems (IBIS) Fossil fuel emission

INCCA Deforestation Experiment • Do not allow tree PFTs from year 2000 • Perform IPCC A2 scenario Tree PFTs – Not allowed Tropical broadleaf evergreen trees Tropical broadleaf deciduous trees Temperate broadleaf evergreen trees Temperate conifer evergreen trees Temperate broadleaf deciduous trees Boreal conifer evergreen trees Boreal broadleaf deciduous trees Boreal conifer deciduous trees • Will show the net effect of deforestation • Get an Upper bound Other PFTs Evergreen Shrubs Deciduous Shrubs Warm (C4) grasses Cool (C3) grasses

CO 2 is 325 ppmv more but no temperature difference Atmospheric CO 2 Sfc. Temperature Grass world A2 Biogeophysical and biogeochemical effects are comparable so far

INCCA Deforestation Experiment Annual total litter fall Biomass Turn over Times in IBIS Leaf 1-2 years Fine Root -1 year Wood - 50-100 yrs (25-50 for dead tree) Grass world Decline of NPP (3yrs) Grass growth + faster wood turnover Running out of wood All tree leaves fall in year 2000 A2

INCCA Deforestation Experiment: Terrestrial carbon fluxes GPP NPP Soil Respiration A2 Grass world Sharp fall in GPP and NPP due to “Sudden Death” of trees and then rise due to grass land expansion The increased respiration is from larger litter fall from grasses and shrubs

Land becomes a source for ~ 50 years and oceans take up a fraction of this flux Land carbon flux (NEE) Ocean carbon flux ~70 Gt-C/yr Grass world A2

The potential to store carbon in biomass is destroyed Biomass Soil carbon A2 825 Gt-C 1000 Gt-C Grass world 140 Gt-C 170 Gt-C

The Carbon Budget (Grass world – A2): 2000 - 2075 Biomass Difference ~ -1000 Gt-C Where has this gone?

Soil carbon ~ 170 Gt-C Atmosphere ~ 682 Gt-C (325 ppmv) Ocean ~ 148 Gt-C

What to expect of our global deforestation experiment?

Rennsen et al. (2003, GRL) found a global mean cooling of about 3 K Continue our deforested “A2 emission” simulation to year 2300 – The expected biomass difference is 1800 Gt-C (857 ppmv) Even if all of this remains in the atmosphere, the extra warming potential is only ~ 1 K at year 2300 But the albedo-cooling is probably ~ 3 K

More INCCA Deforestation Experiments: Latitude bands

Tropical forests Direct climate effects Likely warming Carbon release effects Warming Net climate effects Likely warming Boreal forests Strong cooling Warming Cooling Mid-latitude forests Cooling Warming ???