University of Washington atmospheric scientist Qiang Fu and his colleagues used a second channel, sensitive almost exclusively to the stratosphere, to quantify this layers exact contribution to channel 2 readings. (scientificamerican.com)
However, researchers have yet to pin down the exact contribution of greenhouse gas emissions and natural variability in the climate. (newscientist.com)
«The exact contribution of natural gas to this overall excess is unknown at this point and there's not enough scientific evidence to figure out how much is contributed by the gas industry,» Brandt notes. (scientificamerican.com)