QUESTIONS 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 (N 2 +3H 2  2NH 3 ) 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 CO 2 varies over geologic time, within the range 190 – 280 ppm for the last 420,000 years. The variations correlate with climate: cold  low CO 2. Is CO 2 driving climate or vice versa? CARBON DIOXIDE: GEOLOGICAL RECORD

THE CURRENT CO 2 OBSERVATION NETWORK

ATMOSPHERIC CO 2 INCREASE OVER PAST 1000 YEARS, AND MORE RECENTLY…

TREND OF CO 2 CONCENTRATIONS

Emissions have increased by more than 2X since But there has not been a corresponding rise in the annual increment of atmospheric CO 2. In 1970 ~75% of the emitted CO 2 stayed in the atmosphere, but only ~40% in GLOBAL FUEL USE 8700 in 2008!

CO 2 Airborne Fraction 0002 RECENT GROWTH IN ATMOSPHERIC CO 2 CONCENTRATIONS The average annual increase did not change much between 1970 and 2000, despite significant increases in fossil fuel emissions. 1 ppm = 2.1 x kg of C (in CO 2 ) Average rate of increase per year, 1.5 ppm = 3.25 x kg/yr—little change (some variations) since Airborne fraction, CO 2 (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 EMISSIONS?

GLOBAL PREINDUSTRIAL CARBON CYCLE Inventories in PgC Flows in PgC yr -1

Photosynthesis: CO 2 + H 2 O + light  "H 2 CO" + O 2 Respiration: "H 2 CO" + O 2  CO 2 + H 2 O + energy Very little organic matter is stored, on average. Dissolution/evasion CO 2(g) + H 2 O + CO 3(aq) =  2 HCO 3 ¯ CARBON CYCLE ON LAND CARBON CYCLE IN THE OCEAN

UPTAKE OF CO 2 BY THE OCEANS CO 2 (g) CO 2. H 2 O HCO H + HCO 3 - CO H + K H = 3x10 -2 M atm -1 K 1 = 9x10 -7 M K 2 = 7x M pK 1 Ocean pH pK 2 Net uptake: CO 2 (g) + CO HCO 3 -- CO 2. H 2 O HCO 3 - CO 3 2- OCEAN ATMOSPHERE H2OH2O

LIMIT ON OCEAN UPTAKE OF CO 2 : CONSERVATION OF ALKALINITY Equilibrium calculation for Alk = 2.25x10 -3 M pCO 2, ppm Ocean pH [CO 3 2- ], M [HCO 3 - ], M [CO 2. H 2 O]+[HCO 3 - ] +[CO 3 2- ], M Ca 2+ + CO 3 2- …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[Mg 2+ ] + 2[Ca 2+ ] - [Cl - ] – 2[SO 4 2- ] – [Br - ] = [HCO 3 - ] + 2[CO 3 2- ] It is conserved upon addition of CO 2  uptake of CO 2 is limited by the existing supply of CO 3 2- Increasing Alk requires dissolution of sediments: CaCO 3 Often called carbonate alkalinity

EQUILIBRIUM PARTITIONING OF CO 2 BETWEEN ATMOSPHERE AND GLOBAL OCEAN Fraction of CO 2 in atmosphere (Equilibrium for present-day ocean, pH=8.2):  only 3% of total inorganic carbon is currently in the atmosphere But CO 2 (g)  [H + ]  F  … positive feedback to increasing CO 2 Pose problem differently: how does a CO 2 addition dN partition between the atmosphere and ocean at equilibrium?  28% of added CO 2 remains in atmosphere! varies roughly as [H + ] varies roughly as [H + ] 2 moles

FURTHER LIMITATION OF CO 2 UPTAKE: SLOW OCEAN TURNOVER (~ 200 years) Inventories in m 3 water Flows in m 3 yr -1 Uptake by oceanic mixed layer only (V OC = 3.6x10 16 m 3 ) would give f = 0.94 (94% of added CO 2 remains in atmosphere)

compare to ~300  moles CO 3 = Observed uptake of fossil fuel CO 2 by the oceans

NET UPTAKE OF CO 2 BY TERRESTRIAL BIOSPHERE (1.4 Pg C yr -1 in the 1990s; IPCC [2001]) is a small residual of large atm-bio exchange Gross primary production (GPP): GPP = CO 2 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 CO 2 observations show that the net uptake is at northern midlatitudes CO 2 + H 2 O  "H 2 CO" + O 2 Photosynthesis and Respiration

CYCLING OF CARBON WITH TERRESTRIAL BIOSPHERE Inventories in PgC Flows 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+ cement5.3 Deforestation1-2 Total – – 2000 Sources Atmospheric accumulation 3.2 Ocean uptake2.1 "Missing Sink"1-2 Total Sinks GLOBAL CO 2 BUDGET [PgC/yr]

EVIDENCE FOR LAND UPTAKE OF CO 2 FROM TRENDS IN O 2,

Harvard Forest, Petersham, MA. A "typical" New England forest…an artifact! NH % of land area in forests Year MA Fitzjarrald et al., 2001

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

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? 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) MODEL OBSERVATIONS

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/yr Total CO 2 source (2008) = 9.9 PgC/yr

FOSSIL FUEL EMISSIONS: US vs CHINA IN 2001

CHINA IS NOW THE WORLD’S LARGEST EMITTER OF CO 2 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 CO 2 emissions

CARBON-CLIMATE FUTURES Vegetation matters! Different models project dramatically different futures using different ecosystem models. ~ 2º K in 2100 Coupled simulations of climate and the carbon cycle

PROJECTED FUTURE TRENDS IN CO 2 UPTAKE BY OCEANS AND TERRESTRIAL BIOSPHERE IPCC [2001]

PROJECTIONS OF FUTURE CO 2 CONCENTRATIONS [IPCC SRES]