On the opening day of COP27, the U.N. climate talks, world leaders emphasized the urgent need to accelerate efforts to reduce pollution and combat global warming. They acknowledged the disruptive effects of the war in Ukraine on global energy markets and highlighted the disproportionate impacts of climate change on poorer nations. SHARM EL SHEIKH — Leaders gathered on Monday to confront the growing climate crisis, which remains complicated by multiple global challenges threatening to delay critical transitions away from fossil fuels. A major concern overshadowing the talks is Russia’s invasion of Ukraine, a conflict largely financed through the sale of…