ESS200A
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)