The different Greenhouse gases have different heat trapping abilities. So, we refer to the global warming potential of different gases
Methane traps more heat than carbon dioxide.
Emissions of one million metric tons of methane is equivalent to emissions of 28 million metric tons (approx.) of carbon dioxide. So, although there is less methane than carbon dioxide, its warming impact is greater.
Water vapour is also a very significant greenhouse gas. As the earth warms, more water evaporates thereby doubling the heat trapping effects of Carbon Dioxide. Similarly, processes like the melting of permafrost, release large amounts of methane