BACKGROUND

Although methane concentrations are much lower than carbon dioxide, per kilogram, methane is 25 times more effective at trapping heat in the Earth's atmosphere compared to carbon dioxide. Methane concentrations have increased by more than 100% since pre-industrial times, indicating that the increased sources due to human activity are much larger than the sinks (reaction with OH^- in atmosphere and oxidation by soil bacteria). Every year, 84 Teragrams (Tg) are in excess in the Earth's atmosphere. Moss et al. (2000) combined literature values into one graph to show that agricultural activities contribute about half of all anthropogenic methane emissions, largely from animal digestion, waste, and rice paddies. More information about methane can be found on the U.S. EPA website: http://epa.gov/methane/.

The table in this set (Table 2) was reconstructed from the Intergovernmental Panel on Climate Change (IPCC) reports from 2007, while the figure in this set is taken from Moss et al. (2000). The IPCC 2007 report, which compiled information from various scientific sources, provides detailed information about methane's contribution to climate change.