From the deck of a boat in New York harbor, the chief executive of Equinor squinted toward a stretch of sea where his oil company will soon build a giant wind farm. “We are doing all we can” to fight climate change , said the executive, Eldar Saetre.

Hours later, at a hotel where Mr. Saetre and fellow oil executives were gathering to defend their industry — a major contributor to global warming — climate protesters weren’t buying it. Using lights, they projected “MAKE BIG OIL PAY” on the facade .

On Monday, as world leaders gathered at the United Nations climate summit and discussed the urgency of slashing carbon dioxide emissions from burning fossil fuels, 13 of the world’s biggest fossil fuel companies presented their defense at a forum across town . But most of their proposals appeared designed to perpetuate the use of oil and gas for decades to come, rather than transition quickly to cleaner options.

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The companies promised a program to invest in technologies to scrub carbon dioxide from the air, although big questions remain about scaling up that technology. They also promised to cut down on leaks of methane, a potent greenhouse gas, from wells and pipes, and reaffirmed support of a tax on the burning of oil, gas and coal.