Many oscillations on different time-scales have been found or hypothesized . Here is a list of known or proposed climatic oscillations. : Some natural periodicities in the sun exist , and these may or may not show up as periodicities in climate : Anomalies in oscillations sometimes occur when they coincide , as in the Arctic dipole anomaly ( a combination of the Arctic and North Atlantic oscillations ) and the longer-term Younger Dryas , a sudden non-linear cooling event that occurred at the onset of the current Holocene interglacial . In the case of volcanoes , large eruptions such as Mount Tambora in 1816 , which led to the Year Without a Summer , typically cool the climate , especially when the volcano is located in the tropics . Around 70 000 years ago the Toba supervolcano eruption created an especially cold period during the ice age , leading to a possible genetic bottleneck in human populations . However , outgassing from large igneous provinces such as the Permian Siberian Traps can input carbon dioxide into the atmosphere , warming the climate . Triggering of other mechanisms , such as methane clathrate deposits as during the Paleocene-Eocene Thermal Maximum , increased the rate of climatic temperature change and oceanic extinctions
Year Without a Summer
Year Without a Summer
Climate oscillation