Nitrous Oxide levels in California much higher than thought
December 9, 2012
• More potent than carbon dioxide,
• No laughing matter
This map shows the amount of nitrous oxide emissions in California (in nanomoles per square meter per second). The "x" represents the location of the measurement tower in Walnut Grove.
The level of nitrous oxide, a potent greenhouse gas, may be 2.5 to 3 times greater than thought in California, according to researchers at Lawrence Berkeley National Laboratory, who used a new method for estimating greenhouse gases that combines atmospheric measurements with model predictions,
At that level, total emissions of nitrous oxide (N2O) — which are believed to come primarily from nitrogen fertilizers used in agricultural production — would account for about 8 percent of California’s total greenhouse gas emissions.
Earlier this year, using the same methodology, the researchers found that levels of methane, another potent greenhouse gas, in California may be up to 1.8 times greater than previous estimates.
“If our results are accurate, then it suggests that N2O makes up not 3 percent of California’s total effective greenhouse gases but closer to 10 percent,” says Marc Fischer, lead researcher on both studies. “And taken together with our previous estimates of methane emissions, that suggests those two gases may make up 20 to 25 percent of California’s total emissions. That’s starting to become roughly comparable to emissions from fossil fuel CO2.”
Accurate estimates of the California’s greenhouse gas emissions are important as the state works to reduce emissions to 1990 levels by 2020, as mandated by a law known as AB 32. The vast majority of the reduction efforts have been focused on carbon dioxide (CO2).
Nitrous oxide, better known as laughing gas, is an especially potent greenhouse gas because it traps far more infrared radiation than both carbon dioxide and methane.
“It’s present in the atmosphere at tiny concentrations — one-thousandth that of CO2 — but it is very potent,” says Mr. Fischer. “It has a global warming potential of approximately 300, meaning it is 300 times more active than CO2 per unit mass. And it’s 10 to 15 times more potent than methane.”
Worldwide levels of N2O have been rising rapidly for decades, and the major culprit was recently confirmed to be the heavy use of nitrogen fertilizers to grow the world’s food. Other less significant sources of N2O emissions include wetlands, animal and industrial waste and automobiles.