There is a clear sign of continuing long-term climate change caused by increasing atmospheric concentrations of greenhouse gases and these have been confirmed in 2015, 2016 and 2017, the World Meteorological Organization (WMO) said Thursday.
Senior WMO scientist Omar Baddour told journalists in Geneva it is confirmed that the three last years are the warmest years on record with 2016 holding the global record, whilst 2017 was the warmest year without an El Nino, which can boost global annual temperatures.
"The year 2017 is equally the second warmest along with 2015. The record is held by 2016 because of the influence of El Nico. If we take out the impact of El Nino, 2017 was the warmest year non-El Nino year," said Baddour.
"The big story is not the temperature, but the change," said Baddour
A consolidated analysis by the WMO of five leading international datasets showed that the global average surface temperature in 2017 was approximately 1.1 degrees Celsius above the pre-industrial era.
The year 2016 remains the warmest year on record (1.2°C above pre-industrial era) said Baddour explaining that data was used from such sources at Nasa, in the United States and the metrological offices of Britain and Japan.
Global average temperatures in 2017 and 2015 were both 1.1° degrees above pre-industrial levels.
The two years are virtually indistinguishable because the difference is less than one-hundredth of a degree, which is less than the statistical margin of error.
"The long-term temperature trend is far more important than the ranking of individual years, and that trend is an upward one, " said WMO Secretary-General Petteri Taalas in a WMO statement.
"Seventeen of the 18 warmest years on record have all been during this century, and the degree of warming during the past three years has been exceptional.
"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," said Taalas.
The globally averaged temperature in 2017 was about 0.46 degrees C above the 1981-2010 long-term average (14.3 degrees C).
In addition to the global warming due to rising greenhouse gas levels in the atmosphere, the climate also has a naturally occurring variability due to phenomena such as El Nino.
El Nino has a warming influence, and La Nina, which has a cooling influence. The strong 2015/2016 El Nino contributed to the record temperature in 2016. By contrast, 2017 started with a very weak La Nina and also finished with a weak La Nina.