sciencetech-blog

comments

A mystery small 'hot spot' in the U.S. Southwest is responsible for producing the largest concentration of the greenhouse gas methane seen over the United States.

The hot spot, near the Four Corners intersection of Arizona, Colorado, New Mexico and Utah, covers only about 2,500 square miles (6,500 square kilometers), or half the size of Connecticut.

Yet a new Nasa map show is produces more than triple the standard ground-based estimate.

The Four Corners area (red) is the major U.S. hot spot for methane emissions in this map showing how much emissions varied from average background concentrations from 2003-2009 (dark colors are lower than average; lighter colors are higher). The hot spot, near the Four Corners intersection of Arizona, Colorado, New Mexico and Utah, covers only about 2,500 square miles.

In each of the seven years studied from 2003-2009, the area released about 0.59 million metric tons of methane into the atmosphere. 

This is almost 3.5 times the estimate for the same area in the European Union's widely used Emissions Database for Global Atmospheric Research.

In the study published online today in the journal Geophysical Research Letters, researchers used observations made by the European Space Agency's Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) instrument, which measured greenhouse gases from 2002 to 2012.

The atmospheric hot spot persisted throughout the study period. 

A ground station in the Total Carbon Column Observing Network, operated by the Department of Energy's Los Alamos National Laboratory, provided independent validation of the measurement.

To calculate the emissions rate that would be required to produce the observed concentration of methane in the air, the authors performed high-resolution regional simulations using a chemical transport model, which simulates how weather moves and changes airborne chemical compounds.

Is this the cause? The Four Corners coal-fired power plant, near Farmington, is one of the targets Nasa wants to investigate as a possible cause of the methane

Research scientist Christian Frankenberg of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, first noticed the Four Corners signal years ago in SCIAMACHY data.

'We didn't focus on it because we weren't sure if it was a true signal or an instrument error,' Frankenberg said.

The study's lead author, Eric Kort of the University of Michigan, Ann Arbor, noted the study period predates the widespread use of hydraulic fracturing, known as fracking, near the hot spot. 

This indicates the methane emissions should not be attributed to fracking but instead to leaks in natural gas production and processing equipment in New Mexico's San Juan Basin, which is the most active coalbed methane production area in the country.

Natural gas is 95-98 percent methane.

Methane is colorless and odorless, making leaks hard to detect without scientific instruments.

'The results are indicative that emissions from established fossil fuel harvesting techniques are greater than inventoried,' Kort said. 

'There's been so much attention on high-volume hydraulic fracturing, but we need to consider the industry as a whole.'

In just one place in the United States do four states meet. The borders of Utah, Colorado, New Mexico, and Arizona intersect at Four Corners, west of the confluence of the Mancos and San Juan Rivers.

Coalbed methane is gas that lines pores and cracks within coal. 

In underground coal mines, it is a deadly hazard that causes fatal explosions almost every year as it seeps out of the rock. After the U.S. energy crisis of the 1970s, techniques were invented to extract the methane from the coal and use it for fuel. By 2012, coalbed methane supplied about 8 percent of all natural gas in the United States.

Frankenberg noted that the study demonstrates the unique role space-based measurements can play in monitoring greenhouse gases.

'Satellite data cannot be as accurate as ground-based estimates, but from space, there are no hiding places,' Frankenberg said.

In March 2014 the Obama Administration announced a strategy to reduce methane emissions under its Climate Action Plan. 

The strategy includes improving the measurement and monitoring of methane emissions and assessing current methane emissions data.