"Climate change is taking place before our eyes," Michel Jarraud, the head of the UN's weather agency, said of the shrinking of ice floating on the Arctic Ocean to a record low in September and other extremes.
And the first 10 months of 2012 were the ninth-warmest since records began in the mid-19th century, with early months cooled by a "La Nina" weather event in the Pacific, according to a report by Jarraud's World Meteorological Organization (WMO).
It also documented severe floods, droughts and heatwaves, in what the UN expected to add to pressure for action at the Nov. 26-Dec. 7 meeting among 200 nations in OPEC member Qatar.
"The message here for this conference is very clear," Christiana Figueres, head of the UN Climate Change Secretariat told Reuters of extremes and rising emissions. "Governments need to hurry up and they need to be much more on track."
Superstorm Sandy, which struck the U.S. east coast after raging through the Caribbean, showed the United States "is not exempt from the vulnerabilities of climate change and that it also needs to do something," she said.
"We have had severe climate and weather events all over the world and everyone is beginning to understand that is exactly the future we are going to be looking about if they don't do something about it," she said.
Rajendra Pachauri, head of the UN panel of climate scientists, said the costs of defences against higher sea levels would rise towards 2100 and could amount to five to 10 percent of gross domestic product of low-lying nations.
And between 75 and 250 million people in Africa alone could face greater stress on water supplies by 2020, hitting food output. "This would further adversely affect food security and exacerbate malnutrition," he said in a speech to the conference.
He said polls showed U.S. public opinion had swung towards wanting more action by President Barack Obama to slow global warming after Sandy. "But whether that's a lasting change it's too early to say," he told Reuters.
China, the United States, the European Union and India are the top emitters. None have announced plans to limit emissions at Doha despite wide pleas for action.
The UN meeting is struggling to overcome disputes about how to extend the Kyoto Protocol, the existing plan for cutting emissions by developed nations that will otherwise expire at the end of the year.
The European Union, Australia and a few other countries are willing to extend but Japan, Russia and Canada have pulled out, arguing that it is meaningless unless emerging nations led by China and India also sign up.
The United States never ratified the 1997 Kyoto pact. Without an extension of Kyoto, developing nations say they won't work for a global deal applicable to all and meant to be agreed by 2015 and enter into force by 2020.
Also, coal-dependent Poland won backing as the host for next year's UN climate talks after OPEC member Qatar, a double act that dismayed environmentalists who say both oppose action to drop fossil fuels and embrace greener energies.
"The prospect of Poland hosting the next global climate conference is hugely concerning. At a time when action is desperately needed, a host country should be firmly committed to climate protection," Greenpeace's Jiri Jerabek said.