ESS101C
Prof.
Jin-Yi Yu
Orbital-Scale Changes in Methane
qThe Vostok ice record shows a series of cyclic variations in methane concentration, ranging between 350 to 700 ppb (part per billion).
qEach Ch4
cycle takes about 23,000
years.
qThis cycle length points to a likely connection with changes in orbital procession.
qThe
orbital procession dominates
insolation changes at
lower
latitudes.
Modern interglacial period
Last interglacial period
(from Earth’s Climate: Past and Future)