Our Common Future Under Climate Change

International Scientific Conference 7-10 JULY 2015 Paris, France

Yao-Hung Chen

Yao-Hung Chen

Methane may be more important than CO2 in South China Sea


By Hsiao-Chun Tseng, Erasmus Mundus Joint Doctorates program

Hsiao-Chun is presenting a poster at the CFCC15 on Day 2.

As an oceanographer who studies greenhouse gases in natural waters, I mostly get asked about carbon dioxide, or CO2. But while it’s the most abundant greenhouse gas, CO2 is not the gas that excites me. Methane is.

And that’s because methane looks to be contributing much more to global warming than CO2, particularly in the South China Sea, which has some important implications for economic development in the region.

Before I get to that, there are some things about methane you need to know.

Methane is emitted in several different ways: when organic matter degrades under anaerobic conditions (wetlands, rice paddies, fresh waters, waste, landfills, and others); when organic matter transforms into fossil fuels (natural gas, coal, oil); and when organic matter is incompletely burned (e.g. biomass and biofuels). It has the ability to trap 86 times more heat in the atmosphere than CO2 and is now responsible for 20% of global warming. 

An IPCC report in 2013 indicated that the global atmospheric concentration of methane has increased 150%, after the industrial era. This increase in methane concentration is very likely caused by human activities, for example fertilizer in the agriculture, fossil fuel burning in the transportation and factories.  

Most research focuses on methane emission from land; as methane concentration is pretty low in seawater, it doesn’t get paid that much attention. But when you consider the fact that oceans take up 2.3 billion hectares of the earth (or 70% of the earth’s surface) it starts to add up.

One of the most populous sea areas is the South China Sea. It’s also what we call, the largest marginal sea in the world (partially enclosed by land, islands, archipelagos, or peninsulas). As marginal seas are partially enclosed by land, they are strongly affected by the human activities and have become one of the most vulnerable sea areas.

We collected 700 water samples in the South China Sea during 6 research cruises, from surface to depths of 4250 m in order to determine methane distributions and the emission from the sea. Using the global warming potential of methane, we calculated the potential magnitude of the greenhouse effect caused by emitted methane.

According to our research results, during the wet season (May through to October) the methane that is emitted from the South China Sea may contribute more to the greenhouse effect than CO2 does.

With the rise of the Asian economy, more factories have been built and more waste water has been produced and discharged to the rivers and coastal areas. It should come as no surprise that the methane emission from the South China Sea has increased significantly. 

With the potential that methane emissions may increase and become responsible for higher percentage of global warming in the future, more research has to be done in order to help us understand more and predict the future. We also need to focus not only on CO2 reduction but also methane and other greenhouse gases in order to mitigate the global warming. 

Hsiao-Chun Tseng has been working in the research projects in Taiwan, Spain and Belgium.  She has joined several research cruises and field work in rivers, lakes, coastal waters and groundwater. She is currently a PhD researcher at Erasmus Mundus Joint Doctorates program in Marine and Coastal Management.

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