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MADRID (Reuters) - A U.N. climate summit closed on Sunday with major states snubbing calls for tougher action to combat global warming, prompting sharp criticism from smaller countries and environmental activists.

Here are some key quotes from the final days of the COP25 summit:

U.N. Secretary-General Antonio Guterres:

“The international community lost an important opportunity to show increased ambition on mitigation, adaptation and finance to tackle the climate crisis. We must not give up and I will not give up.”

Sofie Nordvik, Norway’s youth delegates:

“We lack the ambition needed to avoid this climate emergency. Our leaders need to step up. The world would have looked very different if young people were in charge today.”

Zhou Yingmin, China’s lead negotiator:

“The results of the meeting did not meet our expectations... I believe everyone regrets that the result was not proportionate to our efforts.”

A woman carries her luggage past a sign of the U.N. Climate Change Conference (COP25) in Madrid, Spain, December 14, 2019. REUTERS/Nacho Doce

Alden Meyer, Union of Concerned Scientists:

“I’ve been attending these climate negotiations since they first started in 1991. But never have I seen the almost total disconnect we’ve seen here at COP25 in Madrid between what the science requires and what the climate negotiations are delivering in terms of meaningful action.”

Carolina Schmidt, president of the talks on behalf of Chile:

“We are all tired.”

“We are of mixed emotions.”

“This has been the longest COP in the history of COPs.”

Ian Fry, Tuvalu representative:

“There are millions of people all around the world who are already suffering from the impacts of climate change. Denying this fact could be interpreted by some to be a crime against humanity.”

Kevin Conrad, Papua New Guinea’s climate envoy:

“Over the last 24 hours, 90% of the participants have not been involved in this process.”

Ronan McNern, a spokesman for civil disobedience group Extinction Rebellion, after dumping a pile of horse manure near the entrance of the summit:

“Out of shit come the best roses. We hope that the international community comes together to create a beautiful future.”

New York Democratic Congresswoman Alexandria Ocasio-Cortez on Twitter:

“An utter failure. COP25 & conferences like it are intended to be actual negotiations to urgently draw down global carbon emissions - not cocktail parties to make politicians feel better about themselves as they squash dissent & sell off our futures to fossil fuel interests.”

Jennifer Morgan, executive director of Greenpeace International:

“This COP exposed the role of polluters in politics and the youth’s deep distrust of government, as climate blockers like Brazil and Saudi Arabia, enabled by an irresponsibly weak Chilean leadership, peddled carbon deals and steamrolled scientists and civil society.”