Scott Doney leads this review session from MIT's Marine Chemistry course, working through the Sigman and Boyle (2000) paper on glacial-interglacial carbon cycle dynamics. The class discusses how carbon isotope records in ocean sediments track past atmospheric CO2 swings, and how biological pumps, deep ocean circulation, and iron fertilization theories fit into explanations for ice-age carbon drawdown. Doney fields student questions that range across the semester's material, tying anthropogenic CO2 uptake by the oceans back to the same isotopic and biogeochemical tools used to reconstruct ancient climate shifts. The format is informal and discussion driven rather than a straight lecture, with students pushing back on interpretations of the paper and Doney clarifying where the field's evidence is solid and where it remains contested. It works as a capstone that pulls together isotope chemistry, ocean circulation, and carbon cycle modeling covered earlier in the course.