14 of the 15 hottest years on record have occurred since 2000, UN says
Fourteen of the 15 hottest years on record have occurred since 2000, according to the UN World Meteorological Organisation, as rising carbon emissions continue to trap heat and drive climate change.
The WMO's new analysis narrowly places 2014 as the hottest recorded since 1850, as have recent analyses from other organisations. The WMO analysis is particularly authoritative as it brings together a number of leading temperature records, as well as alternative ways of estimating the warmth of the globe.
The average global air temperatures over land and sea in 2014 were 0.57C above the average of 14.00C for the 1961-1990 reference period. The record temperature was above those in 2005 and 2010, the next hottest years, but only by a small amount which was within the margin of uncertainty in the calculations.
"The overall warming trend is more important than the ranking of an individual year," said WMO secretary-general Michel Jarraud. "2014 was nominally the warmest on record, although there is very little difference between the three hottest years."
"We expect global warming to continue, given that rising levels of greenhouse gases in the atmosphere and the increasing heat content of the oceans are committing us to a warmer future," he said. "In 2014, record-breaking heat combined with torrential rainfall and floods in many countries and drought in some others - consistent with the expectations of a changing climate."
Global sea-surface temperatures reached record levels in 2014, which is significant because 93% of the heat trapped in the atmosphere by greenhouse gases from fossil fuels and other human activities ends up in the oceans.
The WMO said it was notable that 2014's record temperatures occurred without a fully-developed El Niño event.
These occur when warmer than average seas in the eastern tropical Pacific combine, in a feedback loop, with weather systems to drive up temperatures. The high temperatures in 1998, the hottest year of the 20th century, occurred during a strong El-Niño. On land, England saw its hottest year in three and a half centuries, according to the Central England Temperature data set.
The confirmation of 2014's extreme heat comes ahead of the next round of preparatory UN climate change negotiations in Geneva, starting on 9 February. These are intended to pave towards a global agreement to tackle climate change, the deadline for which is a summit in Paris in December.
The WMO analysis is based, amongst others, on three datasets - Hadcrut, NOAA and NASA - and the analysis from the European Centre for Medium-Range Weather Forecasts.