Methane (CH4) is the main component of natural gas and a potent greenhouse gas (GHG). Upon escaping into the atmosphere, greenhouse gases act as a blanket insulating the Earth, absorbing energy and slowing the rate at which heat leaves the planet. In the case of methane, this energy is absorbed remarkably well.
This process, referred to as the greenhouse effect, occurs naturally, and without it, our planet’s average temperature would fall below freezing. However, with the increase in greenhouse gas emissions over the last few centuries, the greenhouse effect has grown consistently stronger, contributing to the warming of our planet at a rate many consider alarming.
Earth’s second most abundant greenhouse gas after carbon dioxide (CO2), methane is comparatively short-lived. Even so, methane plays a much greater role in warming the planet. Over a 100-year period, methane is 28 times more powerful than carbon dioxide at warming the earth. Over 20 years, that comparison jumps to approximately 80 times.
As methane is emitted into the air, it reacts in several hazardous ways. For one, methane primarily leaves the atmosphere through oxidization, forming water vapor and carbon dioxide. So, not only does methane contribute to global warming directly but also, indirectly through the release of carbon dioxide.
Additionally, during the oxidization process, methane reacts with hydroxyl radicals (OH). These naturally occurring molecules act as a “detergent,” cleaning methane and many other pollutants from the air. Thus, methane reduces the amount of hydroxyl radicals available to remove other types of air pollutants.
Ultimately, reducing the amount of methane in the atmosphere will lessen these effects. By focusing on anthropogenic, or man-made, methane emissions alone, we can decrease the rate of global warming considerably.
GLOBAL WARMING POTENTIALS EXPLAINED
Measured relative to carbon dioxide, global warming potentials (GWP) allow us to compare the impacts of greenhouse gases.
Because carbon dioxide is used as the reference gas, its global warming potential is 1, regardless of the time period over which it is measured. The larger a gas’s global warming potential, the more it will warm the planet compared to carbon dioxide. For example, if a gas has a global warming potential of 50, it means one ton of that gas produces the same average warming as 50 tons of carbon dioxide.
While methane lasts only a decade on average (compared to the 300 to 1,000 years that carbon dioxide remains in the atmosphere), it also absorbs much more energy. The net effect of this shorter lifespan combined with the higher energy absorption is reflected in its global warming potential. And thus, methane has a global warming potential of 28to 36 over a period of100 years.