Worksheet answers

  1. Change the run duration to 200,000 years. Add 4000 Gt C of fossil fuels over 400 years. How much CO2 is there in the atmosphere: (1) before any emissions, (2) at the peak of emissions, (3) at the peak of atmospheric CO2 concentration, (4) at year 5000, (5) at year 10,000, (6) at year 50,000, and (7) at year 200,000?

    (1) 282 ppm, (2) 975 ppm, (3) 1625 ppm, (4) 763 ppm, (5) 687 ppm, (6) 433 ppm (7) 429 ppm.

  2. Does atmospheric pCO2 in the model return to values higher than pre-industrial? How much higher at year 200,000?

    No it does not return to the pre-industrial value, even after 0.2 million years. It is still 147 ppm higher.

  3. Examine the behaviour of the lysocline (CaCO3 "snowline") over time. What is the initial depth? Does it shallow or deepen following CO2 emissions? How long does it take to return to the pre-industrial value?

    Initial depth of about 2.4 km. It goes shallower (ocean acidification). It takes ~62 ky to return to the original depth.

  4. What is the difference between the pre-fossil fuel and post-fossil fuel equilibrium values of: (a) [DIC], (b) [Alkalinity], (c) [CO3], and (d) pH, all in the surface ocean?

    Surface [DIC] increases from 2001 to 2439 μMol kg-1 (+438 μMol kg-1). Surface [Alk] increases from 2301 to 2720 μMol kg-1 (+419 μEquiv kg-1). Surface [CO3] increases from 209 to 211 μMol kg-1 (+2 μMol kg-1, i.e. about the same). Surface pH decreases from 8.16 to 8.07 (-0.09 units).