WASHINGTON — There is a 75 percent chance that 2020 will set a record for the warmest year since instrument-based records began in 1880, the National Oceanic and Atmospheric Administration is projecting, beating out 2016 for the distinction.
This is somewhat unexpected, since there is no declared El Niño event in the tropical Pacific Ocean, which tends to provide a natural boost to global temperatures that are already elevated due to the human-caused buildup of greenhouse gases in the atmosphere.
The NOAA projection, made late last week, is based on statistical modeling now that the first quarter of 2020 is off to a near-record warm start, coming in as the second-warmest January through March period since instrument records began in 1880.
Both Europe and Asia had their warmest first quarter of the year. Only 2016 was warmer during this period, and that year featured an unusually intense El Niño event.
Remarkably, the global temperature differences from average in February and March were among the largest of any of the 1,680 months in the agency’s records. March had the second-largest anomaly of any month, said Deke Arndt, the head of climate monitoring at NOAA’s National Centers for Environmental Information in Asheville, N.C., during a news conference call.
February and March were the warmest two non-El Niño months in NOAA’s temperature database, Arndt said.
He said March was also the 44th-straight March and 423rd-straight month that had global average temperatures at least nominally above the 20th-century average. March has warmed by 1.2 degrees Fahrenheit since 1991, he said.
Despite the lack of an officially declared El Niño, in which temperatures in the tropical Pacific must rise above a particular threshold, ocean temperatures have nevertheless been running above average in recent months, Arndt said, contributing to the warm start to 2020.
He said that in 2016, the anomalous warmth was front-loaded due to El Niño conditions that peaked early in the year, before easing as the El Niño diminished later. The first quarter of this year has run neck and neck with 2016’s temperatures, so that if monthly global average temperatures remain relatively steady during the rest of the year, 2020 will move into the top spot, he said.
The oceans and atmosphere agency also found that there’s a 99.9 percent chance 2020 will end up being a top five-warmest year.
‘‘A lot of that has to do with the fact that the year 2016 became the warmest year on record largely because it was very, very warm in the first half of the year, and it was actually not nearly as impressively warm in the second half of the year,’’ Arndt said. ‘‘So the way this might play out is by staying close to 2016 early on it does look like a better than half probability that we will finish the year warmest on record.’’
NOAA isn’t just making a guess at the final temperature ranking for the year. Instead, scientists are using a statistical model that takes monthly temperatures during the past four decades and generates about 10,000 potential outcomes. With March data included, about three-quarters of the model runs showed 2020 would at least nominally beat 2016.
This model does not incorporate El Niño or La Niña conditions, the latter of which can dampen global average temperatures, so if either of these phenomena develop, the projection may be off target.
Separately, Gavin Schmidt, who leads NASA’s Goddard Institute for Space Studies in New York, put the odds of a record this year at closer to 60 percent, based on NASA’s data set, which has slightly different rankings than has NOAA. However, he said that when applying NOAA’s methods to NASA’s monthly data, the odds would increase to 67 percent.
Other temperature monitoring agencies, such as the United Kingdom’s Met Office, have forecast that 2020 will be one of the five warmest years on record.