claim: However, volcanoes have had very little impact on the last 40 years of global warming.
evidence: The Younger Dryas ( around 12,800 to 11,550 years BP ) was a return to glacial conditions after the Late Glacial Interstadial, which temporarily reversed the gradual climatic warming after the Last Glacial Maximum ( LGM ) started receding around 20,000 BP.