The Physics and Ecology of Mining Carbon Dioxide from the Atmosphere by Plants Dennis Baldocchi Professor of Biometeorology Ecosystem Sciences Division/ESPM University of California, Berkeley University of Illinois, Feb, 2011
Transcript
Slide 1
The Physics and Ecology of Mining Carbon Dioxide from the
Atmosphere by Plants Dennis Baldocchi Professor of Biometeorology
Ecosystem Sciences Division/ESPM University of California, Berkeley
University of Illinois, Feb, 2011
Slide 2
Contemporary CO 2 Record
Slide 3
What We are Told Global Mean Temperature will Increase by about
2 C (3.6 F) if CO 2 Increases to 550 ppm by 2100 Current [CO2] is
over 380 ppm, a 100 ppm increase over pre-industrial levels We are
releasing more than 8 PgC/y (1Pg = 10 15 g) by Fossil Fuel
Combustion and Cement Production
Slide 4
Raupach, IBPG Newsletter Much Confusion about: How Much CO 2 We
can Emit to Prevent Certain Temperature Increase? How Fast Must We
Reduce C Emissions and to What Extent? How Do We Convert
Information on Emissions from PgC/y to Atmospheric Pool Size in
terms of ppm CO 2 ? Information is Needed to Guide What We should
Do?
Slide 5
ESPM 111 Ecosystem Ecology How much is C in the Air?: Resolving
Differences between ppm and PgC? Mass of Atmosphere F=Pressure x
Area=Mass x Acceleration=Mass x g Surface Area of the Globe = 4 R 2
M atmos = 101325 Pa 4 (6378 10 3 m) 2 /9.8 m 2 s -1 = 5.3 10 21 g
air Compute C in Atmosphere @ 380 ppm (380 10 -6 ) PgC/ppm P:
atmospheric pressure p c : partial pressure CO2 m c : molecular wt
of C, 12 g/mole m a : molecular wt of air, 28.96 g/mole
Slide 6
CO 2 in 50 years, at Steady-State 8 GtC/yr, Anthropogenic
Emissions 45% retention; air-borne fraction 8 * 50 * 0.45 = 180
GtC, Net C Fossil Fuel Burden Each 2.19 GtC emitted causes a 1 ppm
increase in Atmospheric CO 2 833 (@380 ppm) + 180 = 1013 GtC,
atmospheric burden 450 ppm is thought to be Threshold to Keep
Global Warming Below +2.0 C (3.6 F). 462 ppm with BAU in 50 years
1.65 times pre-industrial level of 280 ppm BAU C emissions will be
~ 16 to 20 GtC/yr in 2050 To stay under 462 ppm the world can only
emit < 400 GtC of carbon, gross, into the atmosphere! Well Reach
this Threshold in
Landscape Differences On Short Time Scales, Grass ET >
Forest ET Ryu, Baldocchi, Ma and Hehn, JGR-Atmos, 2008
Slide 49
Role of Land Use on ET: On Annual Time Scale, Forest ET >
Grass ET Ryu, Baldocchi, Ma and Hehn, JGR-Atmos, 2008
Slide 50
4a. U* of tall, rough Savanna >> short, smooth Grassland
4b. Savanna injects more Sensible Heat into the atmosphere because
it has more Available Energy and it is Aerodynamically Rougher
Slide 51
5. Mean Potential Temperature differences are relatively small
(0.84 C; grass: 290.72 vs savanna: 291.56 K); despite large
differences in Energy Fluxes--albeit the Darker vegetation is
Warmer Compare to Greenhouse Sensitivity ~2-4 K/(4 W m -2 )
Slide 52
Landscape Modification of Energy Exchange in Semi-Arid Regions:
Theoretical Analysis with a couple Surface Energy Balance-PBL
Model
Slide 53
Conceptual Diagram of PBL Interactions H and LE:
Analytical/Quadratic version of Penman-Monteith Equation
Slide 54
The Energetics of afforestation/deforestation is complicated
Forests have a low albedo, are darker and absorb more energy But,
Ironically the darker forest maybe cooler (T sfc ) than a bright
grassland due to evaporative cooling
Slide 55
Forests Transpire effectively, causing evaporative cooling,
which in humid regions may form clouds and increase planetary
albedo Due to differences in Available energy, differences in H are
smaller than LE Axel Kleidon
Slide 56
Temperature Difference Only Considering Albedo Spring
Conditions, Both Systems Green, Low Rc
Slide 57
Theoretical Difference in Air Temperature: Considering
differences in Albedo and Surface Resistances Savanna is Warmer
than Grassland Summer Conditions, Grass Dead, Trees Transpiring
Different Albedo and Rc
Slide 58
And Smaller Temperature Difference considering PBL, Surface
Roughness (R a ) and albedo.!! Summer Conditions Grass Dead, Trees
Transpiring, Different Rc and Ra
Slide 59
Rectifier Effect Prevents Strong Drawdowns in CO 2
Slide 60
T sfc can vary by 10 C by changing albedo and Rs T air can vary
by 3 C by changing albedo and Rs
Slide 61
T air can vary by 3 C by changing Ra and Rs T sfc can vary by
10 C by changing Ra and Rs
Slide 62
Are Ecological Solutions to Mitigating Global Warming a
Band-Aid? Are they Necessary because they Buy us Time? Or, do they
give Us, as a society, a False Sense of Security to Continue doing
Nothing, or Little? Will They, the Carbon Sinks, be Permanent? Will
Engineering the Environment for Carbon Capture Alone Engender
Unexpected Consequences on the Climate System? Closing
Comments
Slide 63
Knobs We Can Turn Future Carbon Emissions: Kaya Identity
Population Population expected to grow to ~9-10 billion by 2050 Per
capita GDP, a measure of the standard of living Rapid economic
growth in India and China Energy intensity, the amount of energy
consumed per unit of GDP. Can decrease with efficient technology
Carbon intensity, the mass of carbon emitted per unit of energy
consumed. Can decrease with alternative energy C Emissions =
Population * (GDP/Population) * (Energy/GDP) * (C
Emissions/Energy)
Slide 64
Quo Vadis? Sure we'll live, we'll survive, it just might not be
a very nice world., DDB, KTVU Interview, April 18, 2010 We must
Reduce Carbon Emissions Immediately and Dramatically, rather than
looking for Ecological Band Aids To Remove our Dependence on Fossil
Fuel, We Will Need to Re- Design Society which Depends on Energy
for All its Work This will involve Redesigning Energy Production
and Infrastructure, Housing, Transportation Soon! At the most
radical stage, it may even require major Economic (e.g.
Internalizing Externalities) and Government Changes and Major
Reductions in Population Growth Unintended Consequences include
Poverty, Famine, and Conflict whether we make Changes, or Not
Vested Interests are Reluctant to Change Energy/Cost Savings and
Efficiencies Could be Positive
Slide 65
Slide 66
Concluding Issues to Consider Vegetation operates less than of
the year and is a solar collector with less than 2% efficiency
Solar panels work 365 days per year and have an efficiency of 20%+
Ecological Scaling Laws are associated with Planting Trees Mass
scales with the -4/3 power of tree density Available Land and Water
Best Land is Vegetated and New Land needs to take up More Carbon
than current land You need more than 500 mm of rain per year to
grow Trees The ability of Forests to sequester Carbon declines with
stand age There are Energetics and Environmental Costs to soil,
water, air and land use change Changes in Albedo and surface energy
fluxes Emission of volatile organic carbon compounds, ozone
precursors Changes in Watershed Runoff and Soil Erosion
Societal/Ethical Costs and Issues Food for Carbon and Energy Energy
is needed to produce, transport and transform biomass into energy
Forests play positive roles for habitat, biodiversity, carbon
storehouses and resources
Slide 67
How Does Energy Availability Compare with Energy Use? US Energy
Use: 105 EJ/year 10 18 J per EJ US Population: 300 10 6 3.5 10 11
J/capita/year US Land Area: 9.8 10 6 km 2 =9.8 10 12 m 2 = 9.8 10 8
ha Energy Use per unit area: 1.07 10 7 J m -2 Potential, Incident
Solar Energy: 6.47 10 9 J m -2 Ione, CA A solar system (solar
panels, biomass) must be at least 0.1% efficient, working year
round, over the entire surface area of the US to capture the energy
we use to offset fossil fuel consumption Assuming 20% efficient
solar system 8.11 10 10 m 2 of Land Area Needed (8.11 10 5 km 2,
the size of South Carolina)
Slide 68
NASA GISS CO2, ppm + 2C Case
Slide 69
Working Hypotheses H1: Forests have a Negative Feedback on
Global Warming Forests are effective and long-term Carbon Sinks
Landuse change (more forests) can help offset greenhouse gas
emissions and mitigate global warming H2: Forests have a Positive
Feedback on Global Warming Forests are optically dark and Absorb
more Energy Forests have a relatively large Bowen ratio (H/LE) and
convect more sensible heat into the atmosphere Landuse change (more
forests) can help promote global warming
Slide 70
Should we cut down dark forests to Mitigate Global Warming?:
UpScaling Albedo Differences Globally, part 2
Slide 71
Global GPP = 1033 * 110 10 12 m 2 = 113.6 PgC/y
Annually-Integrated Measured GPP ~ 1000 gC m-2 y-1; Peak GPP <
3500 gC m -2 y-1
Slide 72
Its a matter of scale A lot of trees need to be planted to
offset our profligate carbon use US accounts for about 25% of
Global C emissions 0.25*8.0 10 15 gC = 2.0 10 15 gC Per Capita
Emissions, US 2.0 10 15 gC/300 10 6 = 6.66 10 6 gC/person Ecosystem
Service, net C uptake, above current rates ~200 gC m -2 Land Area
Needed to uptake C emissions, per Person 3.33 10 4 m 2 /person =
3.33 ha/person US Land Area 9.8 10 8 ha 10.0 10 8 ha needed by US
population to offset its C emissions Naturally!