The first complete temperature datasets for 2017 show that last year was the third in a row of exceptionally warm years, the Copernicus Climate Change Service (C3S) implemented by the European Weather Centre (ECMWF) can announce.
One dataset, produced by ECMWF, shows that the global average surface air temperature exceeded 14.7°C, making 2017:
- about 0.1°C cooler than the warmest year on record, 2016, and warmer than the previous second warmest year, 2015
- the warmest year on record not influenced by warming El Niño conditions in the tropical Pacific
- around 0.5°C warmer than the 1981–2010 climatological reference period
- an estimated 1.2°C warmer than the pre-industrial value for the 18th century.
Comparable results have been obtained by C3S from a reanalysis dataset produced by the Japan Meteorological Agency (JMA).
The method used to produce the datasets is to combine millions of meteorological and marine observations, including from satellites, with models to produce a complete reanalysis of the atmosphere. The combination of observations with models makes it possible to estimate temperatures at any time and in any place across the globe, even in data-sparse areas such as the polar regions.
The results support the provisional announcement by the World Meteorological Organization (WMO) two months ago that 2017 was set to be among the three warmest years on record. Other datasets used in the WMO announcement, which are derived from monthly climatological data for a smaller number of long-term observing sites, are also expected to concur when they are released shortly. All datasets will contribute to the consolidated statement to be issued by WMO on 2017 temperatures.
Air temperature at a height of two metres for 2017, shown relative to its 1981–2010 average. Source: Copernicus Climate Change Service, ECMWF
Temperatures for 2017 were higher than the 1981–2010 climatological average over most regions of the world. They were most above average over parts of the Arctic. 2017 was close to the warmest year on record despite cooling La Niña conditions both early and late in the year over the equatorial eastern Pacific Ocean. The warmest months of 2016 occurred in the declining phase of a strong El Niño, which also influenced temperatures in 2015, making 2017 the warmest year on record that was not influenced by an El Niño.