This year is likely to be the hottest on record, the UN's weather agency has warned ahead of a global climate summit starting in Paris next week.
Global average surface temperature in 2015 is expected "to reach the symbolic and significant milestone of 1C" above the pre-industrial 1880-1899 era, the World Meteorological Organization (WMO) said on Wednesday.
The group said a combination of a strong El Nino and man-made global warming was behind the rise.
The years 2011-2015 were also the warmest five-year period on record, with many extreme weather events - especially heatwaves - influenced by climate change, the WMO said.
"This is all bad news for the planet," said Michel Jarraud, director-general of WMO, warning that inaction on climate change could see global average temperatures rise by 6C or more.
"You have scenarios assuming very strong decisions, very quick and sharp reduction of greenhouse gases, and you have other scenarios with business as usual, where you end up with predictions of additional warming of five, six degrees, maybe even more. That will very much depend on the decisions [in Paris]."
The report comes days before world leaders assemble in Paris to try to negotiate an agreement to fight climate change. The Paris climate conference (COP21) begins on Monday, bringing together the leaders of more than 190 nations.
With current commitments on greenhouse gas emissions, which cause global warming, running out in 2020, any agreement reached at the meeting could have a big impact for decades to come.
The WMO also warned that global ocean temperatures were unprecedented during the five-year period, and several land areas, including the continental United States, Australia, Europe, South America and Russia, broke temperature records by large margins.
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Meanwhile, levels of greenhouse gases in the atmosphere have risen to a new record every year for the past 30 years.
The WMO also said that 2016 could be even hotter due to El Nino - a natural weather pattern marked by warming sea-surface temperatures in the Pacific Ocean. The current El Nino is one of the strongest on record and is likely to continue into 2016.
"The year whose annual mean temperature is likely to be most strongly influenced by the current El Nino is 2016 rather than 2015," the WMO said.
Source: Al Jazeera and agencies