Climate negotiators failed to strengthen targets to cut emissions or to create a global carbon-trading system, two main goals of the 2015 Paris accord, as the impending US exit from the pact exacerbated challenges to cut record-high planet-warming gases.

Delegates from nearly 200 nations sparred for two weeks in Madrid at the annual United Nations climate summit without setting new emissions targets before next year’s UN convention in Glasgow or creating a framework to reward and encourage efforts to cut emissions.