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The year 2017 was one of the planet's three warmest years on record—and the warmest without El Niño conditions that give rising global temperatures an extra boost, U.S. and UK government scientists announced on Thursday.
The year was marked by disasters around the globe of the kind expected in a warming climate: powerful hurricanes tore up the islands of the Caribbean and the Texas and Florida coasts; Europe experienced a heat wave so severe it was nicknamed "Lucifer"; record-breaking wildfires raged across California, Portugal and Chile; and exceptional rainfall flooded parts of South Asia and the U.S. Midwest and triggered landslides that killed hundreds of people in Africa.
The National Oceanic and Atmospheric Administration's annual State of the Climate: Global Climate Report has been documenting the warming of the planet and the effects of those rising temperatures. With the UK's Met Office, it declared 2017 the third-warmest year, after 2016 and 2015. In a separate analysis, NASA said that 2017 was the second warmest on record, based on a different method of analyzing global temperatures. The World Meteorological Organization said temperatures in 2015 and 2017 were "virtually indistinguishable."
"The annual change from year to year can bounce up and down," Derek Arndt, head of the monitoring branch at NOAA's National Centers for Environmental Information, said during a conference call, "but the long-term trends are very clear."
Nine of the 10 warmest years in 138 years of modern record-keeping have occurred since 2005, and the six warmest have all been since 2010, NOAA noted.
Globally, temperatures in 2017 were 1.5 degrees Fahrenheit (0.8 degrees Celsius) above the 20th Century average, according to the report. The warmth prevailed over almost every corner of the globe, the agencies found. Hot, dry conditions contributed to record wildfires on three continents, droughts in Africa and Montana, and heat waves so intense that planes had to be grounded in Phoenix.
Ocean temperatures also experienced their third-warmest year on record, well after the last strong El Niño conditions dissipated in early 2016. Warm oceans can fuel powerful tropical storms like the three hurricanes that devastated Puerto Rico and other parts of the United States.
El Niño and a Warming Arctic
The reports noted that 2017 was the hottest year on record that did not coincide with El Niño conditions, a periodic warming of surface waters in parts of the Pacific that tends to increase temperatures globally. Gavin A. Schmidt, director of NASA's Goddard Institute for Space Studies, said during the conference call that if you were to remove the influence of the El Niño pattern, the past four years all would have seen record-breaking average temperatures, with each year warmer than the last, including 2017.
Regionally, declining sea-ice trends continued in the Arctic, with a record-low sea-ice extent recorded in the first three months of 2017 and the second-lowest annual average.
The Arctic has been warming faster than the rest of the globe, but scientists have relatively little data on current and historical temperatures there. NASA leans more on interpolation to estimate average temperature change in the region, while NOAA scientists exclude much of the Arctic data instead. It's largely that distinction, the scientists said, that explains the difference in how the two agencies ranked the year.
What's in Store for 2018?
Last year was also the third-warmest for the United States. NOAA's U.S. year-in-review report, released last week, calculated that 2017's weather and climate disasters cost the country $306 billion.
Schmidt said that NASA's models in 2016 correctly predicted that last year would rank second, and that the same models say much the same for 2018.
"It will almost certainly be a top-five year," Schmidt said.