September 27, 2013
Laughing Gas, El Niño And Global Warming
Brett Smith for redOrbit.com - Your Universe Online
Nitrous oxide, commonly referred to as ‘laughing gas,’ is well known for its use on dental patients ahead of a painful procedure. However, a lesser-known fact is that it’s also the third-largest contributor to greenhouse gas emissions after carbon dioxide and methane.
Nitrous oxide emissions typically arise from soil, where microbes break down nitrogen and release nitrous oxide as a result. However, farming – particularly the intense use of synthetic nitrogen-rich fertilizers – has boosted emissions of the greenhouse gas significantly over the last 35 years.
Using a detailed model that simulates local soil temperature and moisture content, MIT scientists were able to reproduce actual nitrous oxide measurements taken around the world. They also discovered certain areas around the world that show a decrease in nitrous oxide emissions during El Niño events, which involve abnormally warm waters in the Pacific Ocean that affect temperature and rainfall patterns around the world. The team also saw emissions increase in some areas during periods of La Niña, which involves colder waters taking over the Pacific.
The findings, which were published in the journal Global Biogeochemical Cycles, indicated a feedback loop that involves climate change fueling nitrous oxide emissions and vice versa.
“If more emissions are released into the atmosphere, there will be more global warming … and with higher temperatures, we would have more nitrous oxide coming out,” explained study researcher Eri Saikawa, an assistant professor of environmental studies at Emory University. “Many people may not consider the nitrogen cycle, but we do have to realize it is pretty important.”
For many areas around the planet, the MIT computer model’s calculations matched observations. Saikawa noticed a significant correlation with the El Niño/La Niña climate pattern and nitrous oxide emissions, particularly near the equator. She explained that the weather patterns’ effect on emissions makes sense in light of the observation that rainfall patterns caused by La Niña and drought patterns caused by El Niño in South Asia correlated to increases and decreases in nitrous oxide emissions respectively.
“We thought we would see some variability, but we didn’t think it would be this significant,” Saikawa said. “There is a need for more research to really determine what are the possible impacts from future climate change.”
William Horwath, a professor of soil bio-geochemistry at the University of California, Davis, praised the group’s model, but said a more refined model should incorporate many more factors, such as the presence of microbe-affecting iron in the local soils.
“Future modeling studies stand to gain valuable information by considering iron among the regional drivers of N2O emission,” Horwath said.
The study authors said they plan to incorporate global agricultural factors into their next model, to see how certain fertilizers impact nitrous oxide emissions. Co-author Ron Prinn, a professor of atmospheric science at MIT, singled out the agricultural practices of Brazil as a major driver of nitrous oxide emissions. The South American country is increasingly planting and fertilizing biofuel crops, he says, tearing down forests in the process.
“Brazil and other countries are very concerned about the sustainable production of biofuels in the future,” Prinn said. “What damage will it do to soil health? … Will they be making biofuels that are causing nitrous oxide and carbon dioxide emissions?”
“We should think about the impact that we have from our agricultural activities,” Saikawa said. “Over-fertilizing our soil could be potentially quite damaging for the climate and also for the ozone.”