Claim: The Arctic’s carbon bomb might be even more potent than we thought […] methane, a shorter-lived but far harder-hitting gas that could cause faster bursts of warming

Relevance (1 = gold evidence, 0 = mined hard negative): 1
Passage: Melting of this ice may release large quantities of methane, a powerful greenhouse gas into the atmosphere, causing further warming in a strong positive feedback cycle and marine genus and species to become extinct.

Relevance (1 = gold evidence, 0 = mined hard negative): 1
Passage: Melting of this ice may release large quantities of methane, a powerful greenhouse gas into the atmosphere, causing further warming in a strong positive feedback cycle.

Relevance (1 = gold evidence, 0 = mined hard negative): 1
Passage: The current Arctic warming is leading to ancient carbon being released from thawing permafrost, leading to methane and carbon dioxide production by micro-organisms.

Relevance (1 = gold evidence, 0 = mined hard negative): 1
Passage: Release of methane and carbon dioxide stored in permafrost could cause abrupt and severe global warming, as they are potent greenhouse gases.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: On a 20-year timescale, a mass of methane is about 85 times more powerful than carbon dioxide at warming the Earth, but on a 100-year timescale, it is only about 28-34 times more powerful, because the carbon dioxide continues to warm the earth after the methane is gone.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: While the lifetime of atmospheric methane is relatively short when compared to carbon dioxide, with a half-life of about 7 years, it is more efficient at trapping heat in the atmosphere, so that a given quantity of methane has 84 times the global-warming potential of carbon dioxide over a 20-year period and 28 times over a 100-year period.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: Methane in the Earth's atmosphere is a strong greenhouse gas with a global warming potential (GWP) 104 times greater than CO2 in a 20-year time frame; methane is not as persistent a gas as CO2 (assuming no change in carbon sequestration rates) and tails off to about GWP of 28 for a 100-year time frame.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: Methane is a significantly more potent greenhouse gas than carbon dioxide in the amount of heat it can trap, especially in the short term.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: Additionally, the global warming induced thawing of the permafrost, which stores about two times the amount of the carbon currently released in the atmosphere, releases the potent greenhouse gas, methane, in a positive feedback cycle that is feared to lead to a tipping point called runaway climate change.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: Further, methane is a potent greenhouse gas as it is released into the atmosphere, so it causes warming, and as the ocean transports this warmth to the bottom sediments, it destabilizes more clathrates.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: Methane is a major target greenhouse gas and in the 4th protocol report of the Intergovernmental Panel on Climate Change (IPCC) is recommended to increase from a x23 to x72 multiplier because of the magnitude of its effect relative to carbon dioxide and short longevity in Earth 's atmosphere.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: The Woods Hole Research Center, citing two 2015 studies on permafrost carbon says there may be a self-reinforcing tipping point where an estimated equivalent of 205 gigatons of carbon dioxide in the form of methane could cause up to 0.5 °C (up to 0.9 °F) warming by the end of the century, which would trigger more warming.