A satellite that measures the potent global-warming gas methane in the atmosphere has found a surprising hot spot over the southwestern United States.
That result hints that US Environmental Protection Agency considerably underestimates leaks of methane, which is also called natural gas.
The hot spot appeared over the Four Corners area of New Mexico, Colorado, Arizona and Utah.
It contains about 0.60 million kilograms of methane a year, about 80 per cent more than the EPA figured.
That amount would trap more heat than all the carbon dioxide produced yearly in Sweden.
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University of Michigan scientist Eric Kort said the methane likely comes from leaks as workers extract natural gas from coal beds, and not from hydraulic fracturing, called fracking.
The study was released on Thursday by the journal Geophysical Research Letters.
