ESS220
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)