OSLO • Last year was the second or third warmest on record behind 2016, and the hottest without an extra dose of heat caused by an El Nino event in the Pacific Ocean, the United Nations has said.
Average surface temperatures last year were 1.1 deg C above pre-industrial times, creeping towards 1.5 deg C, the most ambitious limit for global warming set by almost 200 nations under the 2015 Paris climate agreement.
The agreement has been weakened by a plan by United States President Donald Trump, who doubts mainstream scientific findings that warming is driven by man-made greenhouse gases, to pull out of the pact.
The UN's World Meteorological Organisation (WMO) said last year was indistinguishable from 2015 as the second or third warmest year behind 2016, and made last year "the warmest year without an El Nino" in records dating back to the late 19th century.
Temperatures in both 2016 and 2015 were lifted by an El Nino, a natural event which can disrupt weather patterns worldwide every few years and releases heat from the tropical Pacific Ocean into the atmosphere.
The WMO said 17 of the warmest 18 years since records began in the 19th century have now happened since 2000, confirming a warming trend driven by man-made greenhouse gases.
A CLEAR PROBLEM
When even the 'colder' years are rewriting the warmest year record books, we know we have a problem.
PROFESSOR DAVE REAY, chair in carbon management at the University of Edinburgh.
"We're in a long-term warming trend despite the ups and downs you get on an annual basis, even a decadal basis," said Dr Gavin Schmidt, of Nasa's Goddard Institute for Space Studies, whose data is used by the WMO.
Professor Dave Reay, chair in carbon management at the University of Edinburgh, said: "When even the 'colder' years are rewriting the warmest year record books, we know we have a problem."
Among extreme weather events last year, the Caribbean and the US suffered a battering from hurricanes, the Arctic ended the year with the least sea ice for mid-winter, and tropical coral reefs suffered from high water temperatures.
"Arctic warmth has been especially pronounced and this will have profound and long-lasting repercussions on sea levels, and on weather patterns in other parts of the world," WMO secretary-general Petteri Taalas said in a statement.
HITTING RECORDS MORE OFTEN
From 1900 to 1980, a new temperature record was set on average every 13.5 years; however, since 1981 it has increased to every three years.
THE US NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION
The findings, which match a projection by the WMO in November, now have full-year data from Nasa, the US National Oceanic and Atmospheric Administration (NOAA) and Britain's Met Office with the University of East Anglia. "From 1900 to 1980, a new temperature record was set on average every 13.5 years; however, since 1981 it has increased to every three years," NOAA said.
The 2015 Paris agreement, which seeks to shift the world economy from fossil fuels this century, aims to limit temperatures to "well below" a rise of 2 deg C above pre-industrial times while pursuing efforts to limit it to 1.5 deg C.
Mr Omar Baddour, WMO scientific coordinator, said temperatures could reach 2 deg C above pre-industrial times by 2060 to 2070.
"It's alarming, actually," he told a news briefing in Geneva of the ever more frequent records.
In the US alone, weather and climate-related disasters cost a record US$306 billion (S$404 billion) last year, NOAA said last week.
Mr Robert Glasser, the UN Secretary-General's Special Representative for Disaster Risk Reduction, described the pace of climate change as "an existential threat to the planet" that required a "drastic response".
Mr Bob Ward, of the London School of Economics, said the heat "should focus the minds of world leaders, including President Trump, on the scale and urgency of the risks that people, rich and poor, face around the world from climate change".