Why Global Warming: Why Is Methane So Important?

1. Introduction:

It is certainly known we are changing the climate and, as an example, we have many new symptoms since 1950s, such as increased sea level, warmed oceans and atmosphere, or decreased amounts of snow and ice (IPCC, 2013).

We recognize as well that the atmospheric concentrations of the greenhouse gases carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) have increased since 1750 in an exceptional form in the last 22,000 years due to anthropogenic activity (Figure 1). However, scientists have difficulties to understand how the climate is changing and how it is going to change in the future (IPCC, 2013).

2. Why is methane so important? :

Fortunately, methane concentrations in the atmosphere are 200 times lower than concentrations of carbon dioxide. On the contrary, concentration of CH4 has increased by 150% since pre-industrial times compared to only 20% and 40% for N2O and CO2, respectively. As a greenhouse gas, methane is 20 times more potent than carbon dioxide, trapping much more heat (IPCC, 2013).

GHGs are

Methane sources and sinks:

“Although most sources and sinks of methane have been identified, their relative contributions to atmospheric methane levels are highly uncertain” (Kirschke et al., 2013).

Methane emissions can be divided into three different groups according to Kirschke et al: biogenic, thermogenic and pyrogenic.

- Biogenic sources: they include microorganisms which generate methane as a metabolic product, rice paddies, natural wetlands, oxygen-poor reservoirs, rumiants, termites, etc.

- Thermogenic sources: they contain methane emitted through the use of fossil fuels (oil, coal and natural gas) and vented through natural seeps and volcanic activity.

- Pirogenic sources: they are originated by partial combustion of fossil fuels and biomass.

All of these different emissions have different isotopic concentrations and this can be used, as explained before, to find out the source if we focus on the atmospheric