The figure above shows the column-averaged mixing ratio of methane in parts per billion (ppb). For example, 1730 ppb means that one billion air molecules contain 1730 methane molecules. The large map on the top left shows a multi-year average of the global methane distribution as retrieved from SCIAMACHY on ENVISAT. As can be seen, methane is somewhat higher over the northern hemisphere where most of the methane sources are located. These sources are, for example, wetlands, rice fields, gas and oil production, coal mining and ruminants (e.g., cattle and sheeps). Shown in red are major source regions such as China, India, Siberia and parts of the tropics. Methane varies strongly with the season as shown in the maps on the right. The bottom figure (red curve) shows that methane started rising at around 2007 after several years of stability. The reason for this is not yet fully understood. As can also be seen, the amount of methane varies significantly within each year, e.g., with the season.