Claim: However, volcanoes have had very little impact on the last 40 years of global warming.

Relevance (1 = gold evidence, 0 = mined hard negative): 1
Passage: Notable eruptions in the historical records are the 1991 eruption of Mount Pinatubo which lowered global temperatures by about 0.5 °C (0.9 °F) for up to three years, and the 1815 eruption of Mount Tambora causing the Year Without a Summer.

Relevance (1 = gold evidence, 0 = mined hard negative): 1
Passage: The eruption had a noticeable impact on growth conditions in the Northern Hemisphere, which were the worst of the last 600 years, with summers being on average 0.8 °C (1.4 °F) colder than the mean.

Relevance (1 = gold evidence, 0 = mined hard negative): 1
Passage: The consensus is that several factors are important: atmospheric composition, such as the concentrations of carbon dioxide and methane (the specific levels of the previously mentioned gases are now able to be seen with the new ice core samples from EPICA Dome C in Antarctica over the past 800,000 years); changes in the earth's orbit around the Sun known as Milankovitch cycles; the motion of tectonic plates resulting in changes in the relative location and amount of continental and oceanic crust on the earth's surface, which affect wind and ocean currents; variations in solar output; the orbital dynamics of the Earth–Moon system; the impact of relatively large meteorites and volcanism including eruptions of supervolcanoes.

Relevance (1 = gold evidence, 0 = mined hard negative): 1
Passage: 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.

Relevance (1 = gold evidence, 0 = mined hard negative): 1
Passage: "Volcanic influence on centennial to millennial Holocene Greenland temperature change".

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: IPCC AR4 WG1 Ch9 2007, p. 690: "Recent estimates indicate a relatively small combined effect of natural forcings on the global mean temperature evolution of the second half of the 20th century, with a small net cooling from the combined effects of solar and volcanic forcings."

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: In the modern era, emissions to the atmosphere from volcanoes are approximately 0.645 billion tonnes of CO 2 per year, whereas humans contribute 29 billion tonnes of CO 2 each year.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: Volcanic eruptions of a large magnitude can impact global climate, reducing the amount of solar radiation reaching the Earth's surface, lowering temperatures in the troposphere, and changing atmospheric circulation patterns.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: The opposite effect is volcanism, responsible for the natural greenhouse effect, by emitting CO2 into the atmosphere, thus affecting glaciation (Ice Age) cycles.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: A massive volcano eruption would eject extraordinary volumes of volcanic dust, toxic and greenhouse gases into the atmosphere with serious effects on global climate (towards extreme global cooling: volcanic winter if short-term, and ice age if long-term) or global warming (if greenhouse gases were to prevail).

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: Volcanoes are also part of the extended carbon cycle.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: Although the initial carbon dioxide in the atmosphere of the young Earth was produced by volcanic activity, modern volcanic activity releases only 130 to 230 megatonnes of carbon dioxide each year.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: Volcanoes are a large natural source of aerosol and have been linked to changes in the earth's climate often with consequences for the human population.