1 Bioenergy Australia Conference, November 25-26, 2013, Hunter Valley, Australia Climate impacts of bioenergy: Beyond GHGs Ryan M. Bright 1, Rasmus Astrup.

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Bioenergy Australia Conference, November 25-26, 2013, Hunter Valley, Australia

Climate impacts of bioenergy: Beyond GHGs

Ryan M. Bright1, Rasmus Astrup2, Anders H. Strømman1, Clara Antón-Fernández2 , Maria Kvalevåg3, Francesco

Cherubini1

1Industrial Ecology Program, Norwegian University of Science & Technology (NTNU), Trondheim, Norway

2Norwegian Forest and Landscape Institute, Ås, Norway3Center for International Climate & Environmental Research – Oslo (CICERO),

Norway

2 Climate – Ecosystem Dynamics

Source: G. Bonan, Ecological Climatology (2008)

Terrestrial ecosystems and climate are closely coupled systems

Land cover – especially the type of vegetation – affects climate due to variation in albedo, soil water, surface roughness, the amount of leaf area from which heat can be exchanged, and rooting depth

In addition to GHGs, a change in land cover will thus perturb climate by influencing the fluxes of energy, water vapor, and momentum exchanged with the atmosphere

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Land Surface Biogeophysics Albedo largely determines the amount of net radiation (Rn ,

i.e., available energy) at the surface getting partitioned into latent heat, sensible heat, or a ground heat

Rn = (1-α)SW↓ + (LW↓ - LW↑) = H + λE + G

Source: G. Bonan, Ecological Climatology (2008)

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Surface Biogeophysics Changes in albedo (i.e., from vegetation change) lead to an

external forcing at the surface and top-of-atmosphere. This can directly affect local and global climate.

The net local climate effect (near surface temps.) will be determined by the efficiency with which the remaining net radiation is partitioned into sensible, latent, and ground heat fluxes via convective and conductive heat transfer. This is governed largely by surface roughness, plant physiology, and hydrology.

Source: G. Bonan, Ecological Climatology (2008)

5 Land Surface Biogeophysics and Hydrology Apart from climate, plant physiology governs hydrological

processes like transpiration (rooting depth, leaf stomata) and evaporation (canopy interception/LAI) and in turn the partitioning of turbulent heat fluxes into latent heat and sensible heat.

Source: G. Bonan, Ecological Climatology (2008)

6 Land Surface Biogeophysics: Roughness Surface roughness is mostly determined by vegetation height

which transfers momentum to the surface facilitating convective sensible heat and water vapor (latent heat) exchange from the surface to the atmosphere.

Rn = (1-α)SW↓ + (LW↓ - LW↑) = H + λE + G

Source: G. Bonan, Ecological Climatology (2008)

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Mesoscale circulations Changes in

vegetation properties can influence mesoscale circulation patterns (and regional climate)

Example: Cross-section of a dry patch of grass (black bar) surrounded by wet forests on a summer day

Hot dry air above the grass is forced upward; cool, moist air above the forests subsides

Source: G. Bonan, Ecological Climatology (2008)

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Selected Case Studies

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Analysis of observed biogeophysical contributions to local climate (near-surface temps) due to LUC/LCC (~2 Mha) on the Brazilian cerrado From natural vegetation crop/pasture From crop/pasture sugarcane

Biogeophysical effects considered: Evapotranspiration Surface albedo

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Nat. veg. Crop = +∆T; Crop Sugarcane = -∆T

Nat. veg. Crop = - ∆ET; Crop Sugarcane = + ∆ET

Nat. veg. Crop = +∆alb; Crop Sugarcane = +∆alb

MODIS Observations

Source: Loarie et al., Nature Climate Change (2011)

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Study Insights Conversion of natural vegetation to crop/pasture

warms the cerrado by an average of ~1.6 C Conversion of crop/pasture to sugarcane cools the

region by an average of ~0.9 C Both land cover types are warmer than natural

vegetation Evapotranspiration dominates biogeophysical

(direct) drivers of local climate in the region ETNat. Veg. > ETSugarcane > ETCrop/pasture

Biofuel policy implications? Discourage area expansion into natural vegetation areas

(deforestation); promote local crop substitution (crop/pasture sugarcane) instead

Biophysical factors are important: they can either counter of enhance climate benefits of bioenergy

Source: Loarie et al., Nature Climate Change (2011)

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Climate modeling simulation of replacing annual crops with perennial crops in the U.S. Midwest for bioenergy (~84 Mha)

Biogeochemical factors: Life-cycle GHGs from crop and transportation biofuel (EtOH)

production Displaced fossil fuel emissions in transport sector

Biogeophysical factors: ∆ Surface albedo ∆ Evapotranspiration

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A: Perennials minus annuals

B: Same as A, but albedo of perennials = annuals

C: Same as A, but rooting depth of perennials increased to 2 m

Source: Georgescu et al., PNAS (2011)

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Study Insights

Local and regional cooling from enhanced evapotranspiration

Local, regional, and global cooling from higher surface albedo

Albedo impacts alone are ~ 6 times greater than annual biogeochemical effects from offsetting fossil fuel use

Results demonstrate that a thorough evaluation of costs and benefits of bioenergy-related LUC/LCC must include potential impacts on the surface energy and H2O balance to comprehensively address important concerns for local, regional, and global climate change

Source: Georgescu et al., PNAS (2011)

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Analysis of biogeophysical climate drivers in managed boreal forests of Norway (observation-based) Clearcut vs. Mature coniferous stands Clearcut vs. Deciduous stands Decidous vs. Coniferous stands

Analysis of direct global climate impacts of alternative forest management scenarios: carbon cycle + albedo dynamics (empirical modeling-based)

16 Mircoclimate: Biogeophysical Contributions ∆Temperature between a mature coniferous and: (a)

a clear-cut stand (b) a deciduous stand

Contributions from ∆Albedo (green) dominate 6-yr. mean ∆Temp.

Clear-cut and deciduous stands are cooler than coniferous stands Source: Bright et al., Global Change

Biology (2013)

17 Global climate: Including albedo

In a scenario in which: Harvest intensities are increased (e.g.,

for bioenergy) Harvested conifer stands are allowed

to naturally regenerate with native deciduous species

∆Albedo (blue) offsets ∆NEE (CO2, red) = net medium- & long-term global climate cooling

Impacts outside the managed forest landscape were excluded But carbon-cycle – climate impacts

from fossil fuel substitution with bioenergy are likely beneficial

Including albedo changes across the forested landscape is necessary to avoid sub-optimal climate policy in boreal regions

Source: Bright et al., Global Change Biology (2013)

2010 climateRCP 4.5

RCP 8.5

2010 climate

RCP 4.5

RCP 8.5

Net

∆NEE

∆Albedo

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Included albedo change dynamics in the evaluation of several prominent global forest bioenergy value chains From land use (forest management), not LUC/LCC Changes in forest albedo along one rotation cycle

Life cycle perspective Attributional (no land use baseline/counterfactuals, no system

expansion/avoided emission credits) Metric: Global Warming Potential (GWP), TH = 20, 100, & 500

years Bioenergy products: Heat & Transportation Fuels

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Harvesting forests in regions with seasonal snow cover = high +∆albedo

+∆albedo effects = climate cooling (blue bars), offsets direct biogenic CO2 and life-cycle fossil GHGs

Net cooling for all TH’s for ”CA” (Canada) case

Characterized global direct climate impacts (per MJ wood fuel combusted)

Source: Cherubini, Bright, et al., Env. Res. Letters (2012)

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How to measure?

Coupled climate models (land + atmosphere; land + atmosphere + ocean) Georgescu et al. (2011)

Direct observation (satellite imagery, i.e., MODIS, MERIS, SPOT-VEGETATION, Landsat 7) Loarie et al. (2011)

Hybrid approaches (satellite imagery + simple climate models/metrics) Bright et al. (2011; 2012; 2013); Cherubini et al. (2012)

It is possible to adapt existing climate metrics such as GWP or GTP for albedo Bright et al. (2012, 2013); Cherubini et al. (2012)

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Summary & Conclusions

Climate impact assessments of bioenergy are often incomplete without the inclusion of biogeophysical dimensions Particularly impacts at the local and regional scale

Biogeophysical climate considerations are more relevant to consider: When there is LUC/LCC (i.e., de-/afforestation, crop-switching) In managed forest ecosystems (i.e., time after harvest

disturbance)

Standardized methodologies and metrics do not yet exist

Climate profile of bioenergy? It’s all about land use How we manage our land to procure biomass for bioenergy

dictates climate impacts/benefits, overwhelms life-cycle emission impacts Carbon sinks global climate Biogeophysics and hydrology local and global climate

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Thank You. G. Bonan (2008), Ecological Climatology – Concepts and Applications, 2nd

Edition, Cambridge University Press, Cambridge, U.K. & New York, USA M. Georgescu et al. (2011), Direct climate effects of perennial bioenergy

crops in the United States, PNAS, doi:10.1073/pnas.1008779108 S. Loarie et al. (2011), Direct impacts on local climate of sugar-cane

expansion in Brazil, Nature Climate Change, doi:10.1038/nclimate1067 R. Bright et al. (2013), Climate change implications of shifting forest

management strategy in a boreal forest ecosystem of Norway, Global Change Biology, doi: 10.1111/gcb.12451

F. Cherubini et al. (2012), Site-specific global warming potentials of biogenic CO2 for bioenergy: contributions from carbon fluxes and albedo dynamics, Environmental Research Letters, doi: 10.1088/1748-9326/7/4/045902

R. Bright et al. (2011), Radiative forcing impacts of boreal forest biofuels: A scenario study for Norway in light of albedo, Environmental Science & Technology, doi: 10.1021/es201746b

R. Bright et al. (2012), Climate impacts of bioenergy: Inclusion of carbon cycle and albedo dynamics in life cycle impact assessment, Environmental Impact Assessment Review, doi: 10.1016/j.eiar.2012.01.002

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