Claim: The increase in atmospheric methane, a greenhouse gas, in the latter part of the 20th century was explained as coming from expansion of grazing and rice cultivation, but the cause was found to be leaking gas pipelines in the Soviet Union which are now being properly managed and maintained.

Relevance (1 = gold evidence, 0 = mined hard negative): 1
Passage: In accordance with the IPCC and other natural gas emissions control groups, measurements had to be taken throughout the pipeline to measure methane emissions from technological discharges and leaks at the pipeline fittings and vents.

Relevance (1 = gold evidence, 0 = mined hard negative): 1
Passage: Although the majority of the natural gas leaks were carbon dioxide, a significant amount of methane was also being consistently released from the pipeline as a result of leaks and breakdowns.

Relevance (1 = gold evidence, 0 = mined hard negative): 1
Passage: Methane is an important greenhouse gas with a global warming potential of 34 compared to CO2 (potential of 1) over a 100-year period, and 72 over a 20-year period.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: Increases in atmospheric concentrations of CO 2 and other long-lived greenhouse gases such as methane, nitrous oxide and ozone have correspondingly strengthened their absorption and emission of infrared radiation, causing the rise in average global temperature since the mid-20th century.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: The EPA has determined that greenhouse gas pollution causes global temperature warming, leading to harmful changes to the environment and human health globally such as increased drought and increased famine due to decrease in water supply and agricultural production.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: Human activities are now causing atmospheric concentrations of greenhouse gases—including carbon dioxide, methane, tropospheric ozone, and nitrous oxide—to rise well above pre-industrial levels ... Increases in greenhouse gases are causing temperatures to rise ...

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: Release of greenhouse gases from thawed permafrost to the atmosphere increases global warming.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: Since global warming is attributed to increasing atmospheric concentrations of greenhouse gases such as CO 2 and methane, scientists closely monitor atmospheric CO 2 concentrations and their impact on the present-day biosphere.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: Human activities, primarily the burning of fossil fuels (coal, oil, and natural gas), and secondarily the clearing of land, have increased the concentration of carbon dioxide, methane, and other heat-trapping ("greenhouse") gases in the atmosphere...There is international scientific consensus that most of the warming observed over the last 50 years is attributable to human activities.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: During the late 20th century, a scientific consensus evolved that increasing concentrations of greenhouse gases in the atmosphere cause a substantial rise in global temperatures and changes to other parts of the climate system, with consequences for the environment and for human health.