Weather extremes have hit many countries and the Arctic has seen unprecedented sea ice melt as the world experienced another year among the hottest on record, experts have said.
The years 2001 to 2011 were all among the warmest on record, and this year looks set to be no exception, despite a La Nina weather pattern which has a cooling effect on temperatures, the World Meteorological Organisation (WMO) said.
Every year for the last 20 years has been warmer than the average for 1961-1990, according to three sets of data collected and analysed by scientists in the US and the UK, including one by the Exeter-based Met Office and University of East Anglia.
The Met Office said that, taking uncertainties over measuring global surface temperatures into account, 2012 is very likely to be between the fourth and 14th warmest year in records dating back to 1850.
Dr Peter Stott, head of climate monitoring and attribution at the Met Office, said: “Although the first decade of the 21st century was the warmest on record, warming has not been as rapid since 2000 as over the longer period since the 1970s.
“This variability in global temperatures is not unusual, with several periods lasting a decade or more with little or no warming since the instrumental record began.
“We are investigating why the temperature rise at the surface has slowed in recent years, including how ocean heat content changes and the effects of aerosols from atmospheric pollution may have influenced global climate.”
The UN organisation’s secretary-general Michel Jarraud said climate change was “taking place before our eyes” and would continue to do so as a result of rising greenhouse gas emissions which have reached new record levels this year.