Orbital-Scale Changes in CO2 and CH4
						q Methane (CH4) levels have fluctuated mainly at the 23,000-year orbit rthym of precession.       è These changes may be linked to fluctuations in the strength of monsoon in Southeast Asia. q During glaciations, atmospheric CO2 values have repeatedly dropped by 30% from the levels typical of warm interglaciations.        è Most of the explanation for lower glacial CO2 appears to be tied to a transfer of carbon into the deep ocean. q WHY?