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. (-5[1])Measurements of this quantity at the Mauna Loa Observatory (10[1])are graphed on the Keeling curve. (10[2])This quantity dipped by 90 (10[1])parts-per-million during the last glacial maximum because (10[1])colder oceans are better sinks. (10[2])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■ (10[1])