Methane isn't the most potent greenhouse gas as stated in the article. Water vapor is both the most potent and the most abundant. It also has a positive feedback loop so the hotter the Earth gets, the more water vapor goes into the atmosphere!
Water vapor does amplify the climate effect of other greenhouse gases.
Although, the biggest worry is the stored methane. [1]
The amounts stored are equivalent (in CO2) to about 20-35 years of human activity (2014 CO2 output). If that gets quickly released, who knows what will happen.
I would add that presumably water vapour, methane and carbon dioxide have been in the atmosphere influencing temperatures since before anthropogenic climate change. I imagine rising concentrations of atmospheric water vapour are partly a consequence of emissions of carbon dioxide and methane emissions. (I believe that methane breaks down into chemicals including water.)
I imagine that humans are more responsible for levels of atmospheric water vapour indirectly (through carbon dioxide and methane emissions) than directly.
I imagine temperature and concentrations of atmospheric water vapour are in equilibrium in the absence of changes in the concentrations of other greenhouse gases.
My main reason for answering the parent comment was to suggest that most of any increase in water in the atmosphere might largely result from warming due to other greenhouse gases. It might be the case that global warming is almost solely a function of greenhouse gases other than water vapour, even if it largely had its effect via water vapour.