Methane: Climate change?s 2nd culprit

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Tuesday, September 3, 2013

BECAUSE environmentalists, activists and even scientists themselves give more emphasis on carbon dioxide as the primary culprit of climate change, methane has been placed in the sideways.

“Methane has no direct effects on the climate or the biosphere (and) it is considered to be of no importance.” That was what stated in the first survey in 1971 on the possibility of inadvertent human modification of climate. Likewise, the gas was not mentioned in the index of the major climatology book of the time, H.H. Lamb’s “Climate Past, Present and Future.”

It wasn’t until in 2001, when the Intergovernmental Panel on Climate Change (IPCC) submitted its report that methane was given much attention. “One of the most potent greenhouse gases on Earth,” the report said.


“Methane absorbs heat 21 times more than carbon dioxide and it has 9-15 year life time in the atmosphere over a 100-year period,” says Dr. Constancio Asis, Jr., a recipient of the 2011 Norman E. Borlaug International Agricultural Science and Technology Fellowship Award.

“The Journal Science” reported that atmospheric concentration of methane has more than doubled during the last 300 years and is increasing at an annual rate of about 1 percent each year.

A new study, in the journal “Geophysical Research Letters,” said that methane’s effect on warming the world’s climate may be double what is currently thought. The new interpretations reveal methane emissions may account for a whopping third of the climate warming “from well-mixed greenhouse gases” between the 1750s and today.

Both carbon dioxide and methane are considered greenhouse gases (GHGs), which also include chlorofluorocarbons (CFCs) from air conditioners and refrigerators, and the nitrogen compound, nitrous oxide, from burning fossil fuels and fertilizers. Ground-level ozone, produced by burning fossil fuels, is also considered a greenhouse gas. “Even if we were able to stop them tomorrow, these greenhouse gases will continue to have an effect for centuries,” Secretary-General Michel Jarraud of the UN World Meteorological Organization said in a statement quoted by the Agence France Presse.

First some basics: methane is a very simple molecule (one carbon surrounded by four hydrogen atoms) and is created predominantly by bacteria that feed on organic material. “In dry conditions, there is plenty of atmospheric oxygen, and so aerobic bacteria which produce carbon dioxide are preferred,” explained Dr. Schmidt.

But in wet areas such as swamps, wetlands and in the ocean, there is not enough oxygen, and so complex hydrocarbons get broken down to methane by anaerobic bacteria and are trapped there.

An article written by William F. Ruddiman explores the possibility that methane emissions started to rise as a result of anthropogenic activity 5000 years ago when ancient cultures started to settle and use agriculture, rice irrigation in particular, as a primary food source.

“Rice is a plant that grows best in wet soil, with its roots flooded,” explains L. Hartwell Allen, an American soil scientist at the Crops Genetics and Environmental Research Unit in Gainesville, Florida. “But flooded rice crops emit substantial amounts of methane to the atmosphere.”

In fact, rice fields are one of the major contributors of methane in the atmosphere. “An estimated 19 percent of world’s methane production comes from rice paddies,” admits Dr. Alan Teramura, a botany professor at the University of Maryland. “As populations increase in rice-growing areas, more rice -- and more methane -- are produced.”

The Philippines, being one of the world’s top producers of rice, has contributed much of the methane in the atmosphere. “Rice production in all rice ecosystems grew by more than 428,000 metric tons every year from 2000 to 2010. In 2010-2011, our production grew by 911,743 metric tons,” reported Dr. Flordeliza H. Bordey, socio-economist of the Philippine Rice Institute.

The country’s harvest area also increased to about 4.24 percent. Dr. Bordey said the country registered 47,773 hectares growth per year from 2000-2011. In 2010-2011, harvest area jumped to 182,481 hectares.

Livestock are another major contributor of methane from farming. In 2006, the amount of methane emitted by farm animals alone exceeded that of the iron, steel, and cement industries combined. “Livestock are one of the most significant contributors to today's most serious environmental problems,” said Henning Steinfeld, a senior UN official.

President of the National Academy of Sciences Ralph Cicerone has indicated the contribution of methane by livestock flatulence and eructation to global warming is a “serious topic.” Cicerone, an atmospheric scientist, said: “Methane is the second-most-important greenhouse gas in the atmosphere now. The population of beef cattle and dairy cattle has grown so much that methane from cows now is big. This is not a trivial issue.”

A single cow belches out 100 gallons of methane gas a day. The raising of these animals along with sheep, carabao, and swine has contributed to the methane production in the Philippines.

Among these animals, cattle are by far the largest contributors to global enteric methane emissions, as they are the most numerous and have a much larger body size relative to other species such as sheep and goats.

“If we control methane, which is viable, then we are likely to soften global warming more than one would have thought, so that's a very positive outcome,” said Dr. Drew Shindell, a climatologist at NASA’s Goddard Institute for Space Studies, Columbia University in New York.

Published in the Sun.Star Davao newspaper on September 03, 2013.

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