Forget CO2, what about Methane?

Methane is a greenhouse gas. Therefore, it contributes to the current global issue of global warming. Whilst Carbon Dioxide(CO2) is the primary greenhouse gas which receives the most attention and mitigation policies, Methane(CH4), receives much less attention. Its concentration is only a small fraction of that of CO2 but it has a Global Warming Potential of about 25 times that of CO2 (IPCC, 2007). This therefore makes it a crucial element of the atmosphere which has the potential to strongly impact todays and future climate. Figure 1 shows that even though Methane exists in much lesser quantities, it has followed a similar patter to CO2 in the way which it has expanded over the past 2000 years.

Figure 1

Methane is naturally and anthropogenically sourced. Natural sources include that of methanogenesis which is the process undergone by microorganisms to produce energy. Anthropogenic sources of methane include industrial processes and landfills. Natural and anthropogenic sources of methane are displayed in Figure 2 below. Methane is released in copious amounts under anaerobic conditions. An example of this is when permafrost melts and the carbon matter reaches temperatures where it can decompose and thus produce large amounts of methane (Blog).

Figure 2: Methane Cycle

Methane has a life cycle of approximately 8 years (Fiore et al, 2002). After which it will normally react with Oxygen to form Carbon Dioxide, which is the primary greenhouse gas causing concern for global warming. Thus, it can be concluded that even if all anthropogenic sources of CO2 were eliminated (or mitigated) a large proportion of methane would be converted into CO2.

Paleological records show that in the past methane levels have not altered greatly, but have followed natural variations. However, in the past 100 years, methane levels have diverged from their natural patterns and began an accelerated increase. Today, methane concentrations on a global average are almost triple that of pre-industrial levels (Figure 1). 

The importance of mitigating methane emissions are well highlighted in Johnson & Johnson, 1995. They state that the attractive quality of methane for mitigating as opposed to CO2 is that it has a very short atmospheric life time (8 years), therefore reducing emissions in the present or future will have a much speedier impact. Nevertheless, I believe CO2 will always be of most concern to everyone as it is currently found at such massive concentrations.