A shale gas drilling boom over the last decade has propelled the United States from energy importer to exporter, taking the country a giant leap toward the goal of energy independence declared by presidents for half a century.
Now the upheaval of the domestic energy sector is going global. A swell of gas in liquefied form shipped from Texas and Louisiana is descending on global markets, producing a broader glut and lower energy prices.
The United States was supposed to be a big L.N.G. importer, not a world class exporter. The frenzy of drilling in shale gas fields across the country changed that over the last decade, creating a glut far larger than domestic demand could possibly consume. Companies that spent billions of dollars to build import platforms suddenly had useless facilities until they spent billions more to convert them for export.
The switch will remake the global gas market for decades to come. Energy experts are predicting that the transformation will weaken Russia's dominance over European power markets, help clean the air in cities across China and India by replacing the burning of coal and eventually provide cheaper and cleaner fuel to African villages.
The full dimensions of the wave over the next four or five years, including its impact on the environment and climate change, are hard to predict, in part because they will depend on the policies adopted by many governments. But as several American multibillion-dollar export terminals come on line, few doubt that the influence of more gas, as the cleanest burning fossil fuel, will be consequential for powerful and poor countries alike.