A larger-than-expected historic reduction in this non-dimensionless quantity is explained by Sarmiento and Toggweiler’s three-box model. Increases in this quantity explain the dip in two isotopic signatures in the Suess effect. This quantity is buffered on long timescales via a negative feedback loop in which increases in this quantity raise the rate of silicate weathering. Measurements of this quantity at the Mauna Loa Observatory are graphed on the Keeling curve. This quantity dipped by 90 parts-per-million during the last glacial maximum because colder oceans are better sinks. (10[1])Climate sensitivity is defined as the global temperature increase in response to a doubling of this quantity. Ocean acidification is caused by increases in, for 10 points, what quantity that measures the amount of the primary greenhouse gas emission? ■END■