Methane Impact on Global Climate Change 25% Greater Than Previously Estimated

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CC BY 2.0. Simon Waters

Alarm bells continue to sound about the "other greenhouse gas", methane. Everyone talks about "carbon" - a very unscientific reference to carbon dioxide, which remains the main factor driving global climate change. Methane is also "carbon" in the sense that it is the reduced form of the single carbon atom - CH4 - as opposed to the oxidized form CO2 (carbon dioxide).

A new study suggests that when people talk about "carbon" and climate change, we might be well served to think of both carbon dioxide and methane together.

Methane emissions occur from belching cows, exploitation of oil and gas, agriculture and other sources.

A new study from the University of Reading looks at how methane's absorption of the warm rays from the sun differs from how carbon dioxide acts to warm our atmosphere. Methane absorbs shorter wavelengths, lower in the atmosphere, leading to direct warming of the area closer to the ground. This warmth is further held in, or reflected back towards earth, by clouds.

The overall effect on radiative forcing - which describes the balance of energy from the sun hitting the earth and that reflected back into outer space - shows that methane contributes 25% more towards global warming than the most recent estimates of the Intergovernmental Panel on Climate Change (IPCC) suggest. Methane accounts for 30% contribution of all atmospheric factors towards overall global warming.

Methane already causes complexity in climate change models, because it has a very different rate of breakdown in the atmosphere than carbon dioxide. The outcome of modelling changes significantly, depending on whether one focuses on short-term or long-term factors for the global warming potential of the methane molecule. This issue becomes extremely delicate when trying to assign political value to the emissions of methane versus carbon dioxide.

Any political structures put into place to regulate and incentivize reduction in emissions of global warming pollutants will have to be flexible to adapt itself to the continuing advances in understanding of the effects and importance of various emissions.

Read the whole open source study in: Geophysical Research Letters