If the enhanced
atmospheric warming from a CO2 - induced temperature rise of 1 oC results in enhanced
water vapour that gives an
additional warming of say x oC, the overall warming (doubled CO2 +
water vapour feedback; leaving out other feedbacks for now) will be something like 1.1 * (1 + x + x2 + x3...) or 1.1 / (1 - x)-RSB-.
Methane is an important part of the anthropogenic radiative forcing Methane emissions have a direct GHG effect, and they effect
atmospheric chemistry and stratospheric
water vapour which have
additional impacts natural feedbacks involving methane likely to be important in future — via wetland response to temperature / rain change,
atmospheric chemistry and, yes, arctic sources There are large stores of carbon in the Arctic, some stored as hydrates, some potentially convertible to CH4 by anaerobic resporation [from wikianswers: Without oxygen.