Albedo is the amount of solar energy reflected from the Earth back into space. Earth has an albedo rate of 30%. Higher albedo is equivalent to an increase in reflectivity that raises temperature in the atmosphere. Low albedo cools the atmosphere giving a positive feedback.
Methane (CH4) is a naturally formed gaseous chemical compound. It is a green house gas that can be naturally trapped under arctic ice. Due to the increasing rates of sea ice melting, this trapped gas has made its way into the atmosphere (methane is known as atmospheric methane when it escapes into the atmosphere)