QUESTIONSQUESTIONS

1. How do elements in the lithosphere get transferred to the atmosphere?

2. Imagine an early Earth with a weak Sun and frozen ocean (“snowball Earth”). How would volcanic activity eventually warm the Earth and cause melting of the ocean?

3. Industrial fertilizer (N2+3H2 2NH3) vs. natural fertilizer (compost): how does each affect the nitrogen cycle?

The heavier temperature lines 160,000 BP to present reflect more data points, not necessarily greater variability.

Antarctic Ice Core Data

CO2 varies over geologic time, within the range 190 – 280 ppm for the last 420,000 years. The variations correlate with climate: cold low CO2 .

Is CO2 driving climate or vice versa?

CARBON DIOXIDE: GEOLOGICAL RECORDCARBON DIOXIDE: GEOLOGICAL RECORD

THE CURRENT COTHE CURRENT CO22 OBSERVATION NETWORK OBSERVATION NETWORK

ATMOSPHERIC COATMOSPHERIC CO22 INCREASE OVER PAST 1000 YEARS, INCREASE OVER PAST 1000 YEARS,

AND MORE RECENTLY…AND MORE RECENTLY…

1998-2009 TREND OF CO1998-2009 TREND OF CO22 CONCENTRATIONS CONCENTRATIONS

Emissions have increased by more than 2X since 1970. But there has not been a corresponding rise in the annual increment of

atmospheric CO2. In 1970 ~75% of the emitted CO2 stayed in the atmosphere, but only ~40% in 2000.

GLOBAL FUEL USEGLOBAL FUEL USE8700 in 2008!

0.0

0.2

0.4

0.6

0.8

CO

2 A

irbor

ne F

rac

1960 1970 1980 1990 2000

CO

2 A

irbor

ne F

ract

ion

00 02

RECENT GROWTH IN RECENT GROWTH IN ATMOSPHERIC COATMOSPHERIC CO2 2

CONCENTRATIONSCONCENTRATIONS

The average annual increase did not change much between 1970 and 2000, despite significant increases in fossil fuel emissions.

1 ppm = 2.1 x 1012 kg of C (in CO2)

Average rate of increase per year, 1.5 ppm = 3.25 x 1012 kg/yr—little change (some variations) since 1975.

Airborne fraction, CO2 (ppm)

[IPCC, 2007]

Arrows indicate El Nino events

• atmospheric increase is ~50% of fossil fuel emissions• significant interannual variability

HOW DOES GROWTH RELATE TO FOSSIL FUEL HOW DOES GROWTH RELATE TO FOSSIL FUEL EMISSIONS?EMISSIONS?

GLOBAL PREINDUSTRIAL CARBON CYCLEGLOBAL PREINDUSTRIAL CARBON CYCLE

Inventories in PgCFlows in PgC yr-1

•Photosynthesis:

CO2 + H2O + light "H2CO" + O2

•Respiration:

"H2CO" + O2 CO2 + H2O + energy

Very little organic matter is stored, on average.

•Dissolution/evasion

CO2(g) + H2O + CO3(aq) = 2 HCO3

¯

CARBON CYCLE ON LANDCARBON CYCLE ON LAND

CARBON CYCLE IN THE OCEANCARBON CYCLE IN THE OCEAN

UPTAKE OF COUPTAKE OF CO22 BY THE OCEANS BY THE OCEANS

CO2(g)

CO2.H2O

CO2.H2O HCO3

- + H+

HCO3- CO3

2- + H+

KH = 3x10-2 M atm-1

K1 = 9x10-7 M

K2 = 7x10-10 M pK 1

Ocean pH

pK 2

Net uptake:

CO2(g) + CO32- 2HCO3

--

CO2.H2O HCO3

- CO32-

OCEAN

ATMOSPHERE

H2O

LIMIT ON OCEAN UPTAKE OF COLIMIT ON OCEAN UPTAKE OF CO22::

CONSERVATION OF ALKALINITYCONSERVATION OF ALKALINITY Equilibrium calculation for Alk = 2.25x10-3 M

pCO2 , ppm100 200 300 400 500

8.6

8.4

8.2

2

3

41.4

1.6

1.8

1.9

2.0

2.1

Ocean pH

[CO32-],

10-4 M

[HCO3-],

10-3M

[CO2.H2O]+[HCO3

-]

+[CO32-], 10-3M

Ca2+ + CO32-

…which takes place over a time scale of thousands of years

The alkalinity is the ability of solution to neutralize an acid (or excess positive charge in the ocean balanced by dissolved C):

Alk = [Na+] + [K+] + 2[Mg2+] + 2[Ca2+] - [Cl-] – 2[SO4

2-] – [Br-] = [HCO3

-] + 2[CO32-]

It is conserved upon addition of CO2

uptake of CO2 is limited by the existing supply of CO3

2-

Increasing Alk requires dissolution of sediments:

CaCO3

Often called carbonate alkalinity

EQUILIBRIUM PARTITIONING OF COEQUILIBRIUM PARTITIONING OF CO22

BETWEEN ATMOSPHERE AND GLOBAL OCEANBETWEEN ATMOSPHERE AND GLOBAL OCEAN

Fraction of CO2 in atmosphere (Equilibrium for present-day

ocean, pH=8.2):

only 3% of total inorganic carbon is currently in the atmosphere

But CO2(g) [H+] F … positive feedback to increasing CO2

Pose problem differently: how does a CO2 addition dN partition between the atmosphere and ocean at equilibrium?

28% of added CO2 remains in atmosphere!

2

2 2

( )0.03

( ) ( )CO

CO CO

N gF

N g N aq

varies roughly as [H+]

2

2 2

( )0.28

( ) ( )CO

CO CO

dN gf

dN g dN aq

varies roughly as [H+]2

moles

FURTHER LIMITATION OF COFURTHER LIMITATION OF CO2 2 UPTAKE: UPTAKE:

SLOW OCEAN TURNOVER (~ 200 years)SLOW OCEAN TURNOVER (~ 200 years)

Inventories in 1015 m3 waterFlows in 1015 m3 yr-1

Uptake by oceanic mixed layer only (VOC= 3.6x1016 m3) would give f = 0.94 (94% of added CO2 remains in atmosphere)

compare to ~300 moles CO3=

Observed uptake of fossil fuel CO2 by the oceans

NET UPTAKE OF CONET UPTAKE OF CO22 BY TERRESTRIAL BIOSPHERE BY TERRESTRIAL BIOSPHERE

(1.4 Pg C yr(1.4 Pg C yr-1-1 in the 1990s; IPCC [2001]) in the 1990s; IPCC [2001])is a small residual of large atm-bio exchangeis a small residual of large atm-bio exchange

• Gross primary production (GPP):

GPP = CO2 uptake by photosynthesis = 120 PgC yr-1

• Net primary production (NPP):

NPP = GPP – “autotrophic” respiration by green plants = 60 PgC yr-1

• Net ecosystem production (NEP):

NEP = NPP – “heterotrophic” respiration by decomposers = 10 PgC yr-1

• Net biome production (NBP)

NBP = NEP – fires/erosion/harvesting = 1.4 PgC yr-1

Atmospheric CO2 observations show that the net uptake is at northern midlatitudes

CO2 + H2O "H2CO" + O2 Photosynthesis and Respiration

CYCLING OF CARBON WITH TERRESTRIAL BIOSPHERECYCLING OF CARBON WITH TERRESTRIAL BIOSPHERE

Inventories in PgCFlows in PgC yr-1

Relatively small reservoirs Short time scales net uptake from reforestation is transitory...unless resources are managed to preserve

organic matter

Fossil Fuel+ cement 5.3

Deforestation 1-2

Total 6.3 - 7.3

1980 – 1990 1990 – 2000

Sources

Atmospheric accumulation

3.2

Ocean uptake 2.1

"Missing Sink" 1-2

Total 6.3 - 7.3

Sinks

6.5

.5-1

7-7.5

3.2

1.5-2

1.8-2.8

7-7.5

GLOBAL COGLOBAL CO22 BUDGET [PgC/yr] BUDGET [PgC/yr]

EVIDENCE FOR LAND UPTAKE EVIDENCE FOR LAND UPTAKE OF COOF CO22 FROM TRENDS IN O FROM TRENDS IN O22,,

1990-20001990-2000

Harvard Forest, Petersham, MA. A "typical" New England forest…an artifact!

NH

% o

f la

nd a

rea

in f

ores

ts

20

40

60

80

10

0

Year

1700 1800 1900 2000

MA

Fitzjarrald et al., 2001

HUMAN INFLUENCE ON THE CARBON CYCLEHUMAN INFLUENCE ON THE CARBON CYCLENatural fluxes in black; anthropogenic contribution (1990s) in red

EMISSIONS: WHERE ARE WE NOW?EMISSIONS: WHERE ARE WE NOW?

[Le Quéré et al., 2009]

2.8% drop predicted for 2009 based on IMF GDP

Update: 1.3% drop in 2009, 3% increase for 2010

[Friedlingstein et al., 2010]

SINKS: WHERE ARE WE NOW?SINKS: WHERE ARE WE NOW?

Accumulation in the atmosphere trending up (ocean and/or land uptake efficiency declining? OR?)

[Le Quéré et al., 2009]

Uncertainties here remain LARGE(1-2 PgC/yr)

MODELMODEL

OBSERVATIONS

DEFORESTATION OF THE AMAZON SLOWING DOWN…DEFORESTATION OF THE AMAZON SLOWING DOWN…

[Science, Sept 10, 2010]

47.5% decline!

Survey from the Brazilian Ministry of the Environment

Le Quéré et al. [2009] estimate 2008 deforestation (land use) source of 1.2 PgC/yrTotal CO2 source (2008) = 9.9 PgC/yr

FOSSIL FUEL EMISSIONS: US vs CHINA IN 2001FOSSIL FUEL EMISSIONS: US vs CHINA IN 2001

CHINA IS NOW THE WORLD’S LARGEST EMITTER OF COCHINA IS NOW THE WORLD’S LARGEST EMITTER OF CO22

Population of China (1.3B) is more than 4x the US (307M). Per capita emissions are still 4 times higher in the US.

US and China together currently make up 41% of global CO2 emissions

CARBON-CLIMATE FUTURESCARBON-CLIMATE FUTURES

Carbon Flux: Ocean to Air

-10-8-6-4-202468

10

1850 1900 1950 2000 2050 2100

Pg

C/y

r

Cox et al (2000)

Friedlingstein et al (2001)

Carbon Flux: Land to Air

-10-8-6-4-202468

10

1850 1900 1950 2000 2050 2100

Pg

C/y

r

Atmospheric CO2

200300400500600700800900

1000

1850 1900 1950 2000 2050 2100

pp

m

Global Mean Temperature

13

14

15

16

17

18

19

20

1850 1900 1950 2000 2050 2100

Ce

lsiu

s

Vegetation matters! Different models project dramatically different futures using different ecosystem models.

~ 2º Kin 2100

Coupled simulations of climate and the carbon cycle

PROJECTED FUTURE TRENDS IN COPROJECTED FUTURE TRENDS IN CO22 UPTAKE UPTAKE

BY OCEANS AND TERRESTRIAL BIOSPHEREBY OCEANS AND TERRESTRIAL BIOSPHERE

IPCC [2001]

PROJECTIONS OF FUTURE COPROJECTIONS OF FUTURE CO2 2 CONCENTRATIONSCONCENTRATIONS

[IPCC SRES]