Greenhouse gas concentrations in the atmosphere reached new record highs in 2023, the UN warned on Monday, with countries falling “miles short” of what is needed to curb devastating global warming. “The report’s findings are stark but not surprising — current national climate plans fall miles short of what’s needed to stop global heating from crippling every economy, and wrecking billions of lives and livelihoods across every country,” said UN climate chief Simon Stiell.