1. The sixth element

2. Atmospheric CO 2 Where do emissions come from? How unique are modern CO2 levels? Where does it all go? How long will it stick around?

5. Main Concepts Forms of C Current CO 2 levels and fluxes What are C reservoirs? What are C transfer rates? Why important? Residence time? Timescales of C cycling

10. How much is a gigaton (Gt)? One billion metric tons. It is about 2750 Empire State Buildings. 142 million African elephants. Global C emissions are about 6 Gt.

12. StorageReservoir typeAuthor(s) 750 Gt (1.)In atmosphere, CO2, CH4 (1990)IPCC (1990) (s.) 11,500 Gt (2.)Methane clathratesMacdonald (1992) 38,725 Gt (3.)Dissolved or in suspension in oceansIPCC (1990) (s.) 700 Gt (4.)Dissolved organic C; intermediate & surface watersIPCC. (1990) (s.) 4,000 Gt (5.)Fossil fuelJohns. & Ker. (s.)

14. Calculating Residence time Residence time is a “replacement time”: time required to affect a reservoir given a certain flux.  (years) = reservoir / input rate Example: Residence time of a Stony Brook undergrad Reservoir: Size of Student Body? Input rate: Incoming 1st-year class size

15. Carbon cycle fluxes CyclingFlux rate (Gt/year) Ocean uptake -2.0 Photosynthesis -120.0 Respiration +120.0 Fossil Fuel Combustion +6.0 Biomass burning +1.0 ( “-” means removed from atmosphere)

18. Atmospheric CO 2 : Last 50 years

19. Atmospheric CO 2 : Last 250 years

20. Atmospheric CO 2 : last 400,000 years!

21. Calculating residence time of Carbon due to air-sea exchange Ocean uptake rate: -2.0 Gt / year Total Ocean C reservoir : 39,000 Gt Surface Ocean C reservoir : 600 Gt C residence time (whole ocean) = ? C residence time (surface only) = ?

22. The fate of fossil CO 2 How quickly would the planet take up our CO 2 ? Fast: “solubility pump” Air-Sea CO 2 exchange (centuries) Moderate: “Deep ocean acid neutralization” (tens of thousands of years) Really slow: “Weathering of continental rocks” (millions of years)

23. Moderate C Cycling Neutralize deep ocean acidity by Dissolving ocean CaCO 3 sediments 10 4 years

24. 75% in 300 years 25% “forever”

25. Bottom Line Human C Emissions are large Nature can’t keep up Natural C sinks are diminishing Lifetime of CO 2 from your tailpipe: “300 years, plus 25% that lasts forever”