Claim: Also, it's not yet clear whether changes in stratospheric water vapor are caused by a climate feedback or internal variability

Relevance (1 = gold evidence, 0 = mined hard negative): 1
Passage: Natural changes in the climate system result in internal "climate variability".

Relevance (1 = gold evidence, 0 = mined hard negative): 1
Passage: Broadly speaking, if clouds, especially low clouds, increase in a warmer climate, the resultant cooling effect leads to a negative feedback in climate response to increased greenhouse gases.

Relevance (1 = gold evidence, 0 = mined hard negative): 1
Passage: Models not only project different future temperature with different emissions of greenhouse gases, but also do not fully agree on the strength of different feedbacks on climate sensitivity and the amount of inertia of the system.

Relevance (1 = gold evidence, 0 = mined hard negative): 1
Passage: Attributing detected temperature changes and extreme events to human-caused increases in greenhouse gases requires scientists to rule out known internal climate variability and natural external forcings.

Relevance (1 = gold evidence, 0 = mined hard negative): 1
Passage: Climate change may be due to natural internal processes or external forcings such as modulations of the solar cycles, volcanic eruptions and persistent anthropogenic changes in the composition of the atmosphere or in land use."

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: The feedback due to water vapor is a major factor in determining how much warming would be expected to occur with increased atmospheric concentrations of carbon dioxide, and all existing computer models assume positive feedback — that is, that as the climate warms, the amount of water vapour held in the atmosphere will increase, leading to further warming.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: Since water vapor is a greenhouse gas, the increase in water vapor content makes the atmosphere warm further; this warming causes the atmosphere to hold still more water vapor (a positive feedback), and so on until other processes stop the feedback loop.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: Some examples of climate system feedbacks thought to contribute to recent polar amplification include the reduction of snow cover and sea ice, changes in atmospheric and ocean circulation, the presence of anthropogenic soot in the Arctic environment, and increases in cloud cover and water vapor.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: Lower stratospheric cooling is mainly caused by the effects of ozone depletion with a possible contribution from increased stratospheric water vapor and greenhouse gases increase.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: As warming and evaporation above the Pacific Ocean, temperatures in the lower stratosphere near the [[tropopause]] declined due to both greenhouse gases and [[ozone-depleting substance]]s, reducing [[water vapor]] levels and removing its warming effect, with vapor concentrations below 2.2 [[ppmv]] as measured by the HALOE instrument on the [[Upper Atmosphere Research Satellite]], in the lower stratosphere of the tropics between 5°N - 5°S first being observed since 2001, although a reversal in this pattern is also likely.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: Climate change may be due to internal processes in Earth sphere's and/or following external forcings.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: The main positive feedback in global warming is the tendency of warming to increase the amount of water vapor in the atmosphere, which in turn leads to further warming.

Relevance (1 = gold evidence, 0 = mined hard negative): 0
Passage: Climate change can either occur due to external forcing or due to internal processes.