Methane (CH4)
This potent greenhouse gas is emitted from oil- and gas fields. Methane is released from rice paddies and from places where organic material rots without oxygen, like in marshes and big waste dumps.
  1. Methane is also produced in the digestive system of animals, especially in ruminators like cows.
    Large amounts of methane lie frozen in pockets in the Siberian permafrost areas and in frozen hydrates or clathrates on the sea floor.
    The Global Warming Potential (GWP) of methane is calculated to be 21 times that of CO2.
  1. The increase of methane in the air is associated with the increase in human population and the connected increase in demand for energy, food, water, dwellings and waste dumps.
  1. The content of methane in the atmosphere has increased about 2,5 times since 1750, from roughly 700 parts per billion by volume (ppbv) to 1745 ppbv in year 2000.
    This is an increase by 1060 ppb or 151%.
    The present concentration has not been exceeded during the past 420 000 years.

    There are enormous methane deposits in ocean sediments and in permafrost areas in the Arctic.
    Current emissions from these sediments appear modest for the time being.
    Life span of methane in the atmosphere is relatively short, only between 10-20 years, due to its reaction with oxygen.