From BBC.com (Roger Harrabin):
The acting director of the UK Met Office, Prof Peter Stott, told BBC News: “It’s extraordinary that temperatures in 2017 have been so high when there’s no El Niño. In fact, we’ve been going into cooler La Niña conditions.
“Last year was substantially warmer than 1998 which had a very big El Niño.
“It shows clearly that the biggest natural influence on the climate is being dwarfed by human activities – predominantly CO₂ emissions.”
Figures were published on Thursday by the world’s three main agencies monitoring global temperatures: the UK Met Office and the two US organisations – the US space agency (Nasa) and National Oceanic and Atmospheric Administration (Noaa).
Their datasets are compiled from many thousands of temperature measurements taken across the globe, from all continents and all oceans.
Temperatures for 2017 and 2015 are virtually identical.
Nasa rates 2017 the second hottest year, and Noaa and the Met Office judge it to be the third hottest since records began in 1850.
The Met Office HadCRUT4 global temperature series shows that 2017 was 0.99C (±0.1C) above “pre-industrial” levels – that’s taken as the average over the period 1850-1900.
It was 0.38 (±0.1C) above the 1981-2010 average.
After three consecutive years of record-high temperatures for the globe, Earth was a slightly cooler planet in 2017. But not by much.
Earth’s globally averaged temperature for 2017 made it the third warmest year in NOAA’s 138-year climate record, behind 2016 (warmest) and 2015 (second warmest).
However, unlike the past two years, Earth’s average temperature in 2017 was not influenced by the warming effect of an El Nino, say scientists from NOAA’s National Centers for Environmental Information (NCEI).
The average temperature across the globe in 2017 was 1.51 degrees F above the 20th century average of 57 degrees F. 2017 marks the 41st consecutive year (since 1977) with global land and ocean temperatures at least nominally above the 20th-century average. The six warmest years on record for the planet have all occurred since 2010.
The state of sea ice
Sea ice extent (coverage) at the poles remained low throughout last year. Antarctica had a record-low extent in 2017, while the Arctic had its second-lowest ice coverage on record.
2017, as ranked by other scientific organizations
In a separate analysis of global temperature data released at the same time, NASA scientists ranked 2017 as the second warmest year on record. The minor difference in rankings is due to the different methods used by the two agencies to analyze global temperatures; though over the long term, the agencies’ records remain in strong agreement. Both analyses show that the five warmest years on record all have taken place since 2010.
Analyses from the United Kingdom Met Office and the World Meteorological Organizationoffsite link also ranked 2017 among the top three warmest years on record.
Additional findings from our 2017 report
The month of December: Despite the cooling influence of a weak La Nina in the latter part of the year, December ended up as the fourth warmest December on record for the globe, with an average temperature 1.44 degrees F above the 20th century average. The globally averaged sea surface temperature was the third highest on record, 1.21 degrees F above average. The globally averaged land surface temperature was the third highest on record, 2.36 degrees F above average. Continental warmth: South America had its second warmest year on record; Asia, its third; Africa, its fourth; Europe, its fifth; and North America and Oceania, their sixth. The average Arctic sea ice extent for the year was 4.01 million square miles, the second smallest annual average since record-keeping began in 1979. The average Antarctic sea ice extent for the year was 4.11 million square miles, the smallest annual average since record-keeping began in 1979.