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The sixth element

The sixth element. 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?. Main Concepts. Forms of C Current CO 2 levels and fluxes What are C reservoirs? What are C transfer rates? Why important?

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The sixth element

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  1. The sixth element

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

  3. Main Concepts Forms of C Current CO2 levels and fluxes What are C reservoirs? What are C transfer rates? Why important? Residence time? Timescales of C cycling

  4. 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.

  5. 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

  6. Carbon cycle fluxes ( “-” means removed from atmosphere)

  7. Atmospheric CO2:Last 50 years

  8. Atmospheric CO2:Last 250 years

  9. Atmospheric CO2: last 400,000 years!

  10. 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) = ?

  11. The fate of fossil CO2 How quickly would the planet take up our CO2? Fast: “solubility pump” Air-Sea CO2 exchange (centuries) Moderate: “Deep ocean acid neutralization” (tens of thousands of years) Really slow: “Weathering of continental rocks” (millions of years)

  12. Moderate C Cycling Neutralize deep ocean acidity by Dissolving ocean CaCO3 sediments 104 years

  13. 75% in 300 years 25% “forever”

  14. Bottom Line Human C Emissions are large Nature can’t keep up Natural C sinks are diminishing Lifetime of CO2 from your tailpipe: “300 years, plus 25% that lasts forever”

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