text: A 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 - and is the subject of a major new investigation to find out why. 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. A recent Nasa map shows is produces more than triple the standard ground-based estimate - and researchers say they don't know why.. Scroll down for video . 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. Methane is very efficient at trapping heat in the atmosphere. Like carbon dioxide, it contributes to global warming. 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. Researchers from several institutions are now in the Four Corners region of the U.S. Southwest with a suite of airborne and ground-based instruments, aiming to uncover reasons for a mysterious methane 'hot spot' detected from space. 'With all the ground-based and airborne resources that the different groups are bringing to the region, we have the unique chance to unequivocally solve the Four Corners mystery,' said Christian Frankenberg, a scientist at NASA's Jet Propulsion Laboratory, Pasadena, California, who is heading NASA's part of the effort. Other investigators are from the Cooperative Institute for Research in Environmental Sciences (CIRES) in Boulder, Colorado; the National Oceanic and Atmospheric Administration (NOAA); and the University of Michigan, Ann Arbor. Last fall, researchers including Frankenberg reported that a small region around the Four Corners intersection of Arizona, Colorado, New Mexico and Utah had the highest concentration of methane over background levels of any part of the United States. An instrument on a European Space Agency satellite measuring greenhouse gases showed a persistent atmospheric hot spot in the area between 2003 and 2009. The amount of methane observed by the satellite was much higher than previously estimated. The satellite observations were not detailed enough to reveal the actual sources of the methane in the Four Corners. Likely candidates include venting from oil and gas activities, which are primarily coalbed methane exploration and extraction in this region; active coal mines; and natural gas seeps. Researchers from CIRES, NOAA's Earth Systems Research Laboratory and Michigan are conducting a field campaign called TOPDOWN (Twin Otter Projects Defining Oil Well and Natural gas emissions) 2015, bringing airborne and ground-based instruments to investigate possible sources of the methane hot spot. Shiprock, New Mexico, is in the Four Corners region where an atmospheric methane "hot spot" can be seen from space. Researchers are currently in the area, trying to uncover the reasons for the hot spot. The JPL team will join the effort on April 17 and fly two complementary remote sensing instruments on two Twin Otter research aircraft. The Next-Generation Airborne Visible/Infrared Imaging Spectrometer (AVIRISng), which observes spectra of reflected sunlight, flies at a higher altitude and will be used to map methane at fine resolution over the entire region. Using this information and ground measurements from the other research teams, the Hyperspectral Thermal Emission Spectrometer (HyTES) will fly over suspected methane sources, making additional, highly sensitive measurements of methane. Depending on its flight altitude, the NASA aircraft can image methane features with a spatial resolution better than three feet (one meter) square. In other words, it can create a mosaic showing how methane levels vary every few feet, enabling the identification of individual sources. Hotspot of total column methane anomalies centered over the Four Corners region from 2003 to 2009, when a satellite-based methane-measuring instrument was operational. The April study will focus on verifying the hotspot and determining the methane sources producing the exceptionally elevated methane concentrations. With the combined resources, the investigators hope to quantify the region's overall methane emissions and pinpoint contributions from different sources. They will track changes over the course of the month-long effort and study how meteorology transports emissions through the region. 'If we can verify the methane detected by the satellite and identify its sources, decision-makers will have critical information for any actions they are considering,' said CIRES scientist Gabrielle Pétron, one of the mission's investigators. Part of President Obama's recent Climate Action Plan calls for reductions in methane emissions. The research team also includes scientists from the Institute of Arctic and Alpine Research at the University of Colorado, Boulder; the U.S. Bureau of Land Management; and the state of New Mexico. 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 . 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. 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.
target: Small 'hot spot' responsible for producing the largest concentration of the greenhouse gas methane seen over the United States .
  Area near the Four Corners intersection of Arizona, Colorado, New Mexico and Utah covers 2,500 square miles .
  Hotspot predates widespread fracking in the area .