reporter: this is james henderson, who leads the gas research program at oxford university. james: so, natural gas still emits co2 when burnt. it's not entirely clean. but it's cleaner than its alternatives, like coal, while generating the same amount of energy. and so the first step for many countries is to switch away from dirti fuels such as coal, particularly in power generation, anmove to gas. reporter: you can imagine this like switchg a coal stove for a gas heater, just on a much bigger scale. so, instead of building a new coal power plant, build a gas power plant. or retrofit a coal power plant to run on gas, kind of like the industry is showing off here. so as a lot of relatively clean natural gas became suddenly available, it turned io moreth. it was now -- mr. obama: the bridge fuel that can power our economy with less of the carbon pollution that causes climate change. reporter: the thinking was this -- gas could be the bridge between a fossil-fuel powered past and a future powered by renewables. up until today, politicians and the industry are pushing this narrat

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