The methane hydrate reservoir has largely been ignored as a component of climate change in the Quaternary. However there is growing acceptance that changes in the methane hydrate reservoir played an important role in climate change prior to the Quaternary. The origin of several brief episodes of global warming has been linked with massive dissociation of hydrates and CH4 transfer into the ocean/atmosphere as recorded by large, negative carbon isotope excursions. The remarkable similarity of atmospheric methane (CH4) and temperature variations recorded in ice cores suggests that CH4 played an important role in late Quaternary climate change. We have proposed that the late Quaternary (last 800 kyr) was also a time of significant instability of the methane hydrate reservoir and associated episodic greenhouse climatic forcing due to transfer of CH4 to the atmosphere (Kennett, Cannariato, Hendy and Behl, submitted). Unlike the prevailing interpretation that continental wetlands were the principal source for the rapid atmospheric CH4 increases during the late Quaternary, we suggest a marine sedimentary methane hydrate source. Negligible wetland ecosystems existed during the last glacial episode as a result of global aridity, low sea level, incised, well flushed river systems and low water tables. Wetland ecosystems were insufficiently developed during the last glacial episode to account for the rapid atmospheric CH4 increases during glacial and stadial terminations recorded in polar ice cores. The large, modern wetland ecosystems (peatlands, tropical floodplains, and coastal wetlands) developed almost exclusively during the Holocene, well after the rapid atmospheric CH4 increases during the last glacial termination.