SHARM EL SHEIKH, Egypt — President Biden appeared before an overflowing United Nations convention on Friday to reclaim America’s role as a leader on climate change and to stress a renewed U.S. commitment to stop the planet from catastrophic warming.Mr. Biden came to Egypt as the president who muscled through a landmark climate law, one that provides a record $370 billion to accelerate America’s transition away from the fossil fuels that have underpinned its economy for 150 years.Mr. Biden’s speech came in the midpoint of the two-week summit that has focused not so much on cutting the pollution that is driving climate change, but on the question of what, if anything, industrialized countries owe to poor nations that are suffering climate disasters for which they are ill-prepared and did little to cause.For years, the United States and other wealthy nations have blocked calls for loss and damage funding, concerned that it would open them up to unlimited liability.For the first time, Mr. Biden announced, the U.S. government will require domestic oil and gas producers to detect and fix leaks of methane, a greenhouse gas that traps about 80 times as much heat as carbon dioxide does in the short run."