Above: Departures from average global temperature for the period January-March. Going back to 1880, this year has seen the second warmest January-March period on record. (NOAA/NCEI)
Even without an assist from El Niño, this year is giving 2016 a run for its money as the warmest year on record. In its monthly global climate summary for March, released on Monday, NOAA’s National Centers for Environmental Information (NCEI) reported that last month was the second warmest March in records going back to 1880. The month came in only 0.15°C (0.27°F) behind March 2016.
Last month also saw the third largest departure from the 20th-century average for any of the 1683 months on record, behind only February and March 2016.
NASA concurred with NOAA, as did the Japan Meteorological Agency, with both ranking last month as the second warmest in their respective databases. Meanwhile, Europe's Copernicus Climate Change Service found March 2020 to be the fourth-warmest March on record, but it was within 0.04 degrees of the second- and third-warmest Marches from 2017 and 2019. Such differences in rankings can stem from variations in how research groups analyze global temperature, including how they account for data-sparse areas such as the Arctic.
The crucial difference between this year and 2016 is that one of the strongest El Niño events on record was peaking in late 2015 and early 2016. As it spreads warm water across the surface of the equatorial Pacific Ocean, El Niño can send vast amounts of stored oceanic heat into the atmosphere. Most of the recent record-warm spikes atop longer-term global warming from human-produced greenhouse gases have occurred during El Niño, so to get a March this warm without El Niño is truly noteworthy.
The most notable warmer-than-average temperatures in March were recorded across the eastern half of the United States, much of Asia and southern South America, where temperatures were 3.6 degrees above average or higher.
As was the case throughout most of the winter, the biggest cool anomaly on Earth’s land surface was across parts of western Canada and Alaska.
Could this year become the warmest on record?
One NCEI tool, the Global Annual Temperature Rankings Outlook, is projecting a 75% chance that 2020 will end up as the warmest year in the global database. That projection should be taken with a grain of salt, though. As NCEI explains: “The calculation does not use any weather or climate forecast models. Rather, we utilize simulations of possible outcomes based on how widely the global temperature time series has varied from month to month in the historical record. Once we've created these plausible scenarios, we identify the 95% range of most likely outcomes.”
You might think that the ongoing drop in carbon dioxide emissions from the coronavirus shutdown would be enough to keep 2020 from topping 2016. Indeed, a recent Carbon Brief analysis shows that CO2 emissions might drop several percent over 2019—perhaps by the largest amount in any year on record. But changes in carbon dioxide play out in global temperature largely on the scale of decades to centuries. As we discussed in a post last month, the total effects of the coronavirus shutdown on global temperature in 2020 could be relatively minor.
It might actually be La Niña that throws a spanner into the statistical forecast of a record-hot 2020. Despite the latest monthly outlook from NOAA and the International Research Institute for Climate and Society—which gives only a 30% chance of La Niña conditions by autumn, lower odds than in the March outlook—there are signs in the evolution of the tropical Pacific and in recent model ensembles that a La Niña event may be brewing. If so, that would tamp down the odds of 2020 ending up warmer than 2016 on a global basis.
The latest report from Australia’s Bureau of Meteorology gives further credence to the idea that La Niña may be on the way. All of the eight global climate models in BOM’s latest biweekly roundup, released on Tuesday, predict that the Niño3.4 region of the tropical Pacific will be steadily cooling during the northern summer months.
By September, four of the eight models (BOM, NASA, NOAA, and UKMET) show ocean temperatures in the Niño3.4 region meeting the U.S. criterion for La Niña (0.5°C below the seasonal average, whereas the BOM’s threshold for La Niña is 0.8°C below average, as referred to in the tweet below).
Another clue: the Pacific Decadal Oscillation, as tracked by Nate Mantua (University of Washington), has dipped into negative territory for the first three months of 2020. Research suggests that a negative PDO surrounding the tropical Pacific tends to favor La Niña conditions.
U.S. storminess dominates the global toll of billion-dollar disasters for 2020 thus far
For this year through March, the planet has seen a total of six billion-dollar weather disasters, according to the March 2020 Catastrophe Report from insurance broker Aon. Four of those related to severe weather events in the United States (and this isn’t counting the two major outbreaks thus far in April, one or both of which could top the $1 billion mark in damage).
For more details on global heat and cold records for March and the year to date, see the in-depth post by Dr. Jeff Masters at his Eye of the Storm blog at ScientificAmerican.com.
Brian Donegan contributed to this post.
