Climate summit: U.N. science chief says urgent action is needed against warming.

KATOWICE, Poland — The head of the U.N.’s top science panel on climate change said Tuesday the world needs to “do more and faster” to prevent global warming on a scale that would cause irreversible environmental damage and hit poor societies hard.

Hoesung Lee, who chairs the Intergovernmental Panel on Climate Change, told diplomats at the U.N. climate summit in Poland that scientists had conducted an exhaustive review of data for their recent special report on keeping average global temperature increases to 2.7 Fahrenheit.

“The report shows that not just action, but urgent action is needed,” Lee said.

His comments come as national leaders and ministers gathered in Katowice for the final stretch of the two-week talks, with just days left to break through thorny issues that diplomats have struggled to resolve.

U.N. climate chief Patricia Espinosa urged delegates to show a “spirit of unity” through the end of the week.

Lack of unity was on full display Saturday, when the United States, Russia, Saudi Arabia and Kuwait blocked endorsement of the IPCC’s report. The move prompted anger from environmental groups, who accused the four countries of putting their interests as oil exporters before the need to curb global warming.

Scientists say emissions of greenhouses gases such as carbon dioxide — which is produced through burning of fossil fuels — need to drop significantly by 2030 and reach near-zero by the middle of the century if the 2015 Paris accord’s most ambitious goal is to be achieved.

“We are moving in the right direction in many areas, but we need to do more and faster,” said Lee, adding that cutting emissions sooner would give the world more room for maneuver later.