May 2014 Was the Hottest May in Recorded History

The Citizen's Guide to the Future
June 18 2014 11:30 AM

May 2014 Was the Hottest May in Recorded History

Par7222996
Hot enough for you?

Photo by SAKIS MITROLIDIS/AFP/GettyImages

According to new data released this week, May 2014 is officially the warmest May in recorded history.

Both NASA and the Japan Meteorological Agency have tentatively ranked May at the top of historical measurements, though NASA’s numbers are preliminary because crucial information is still missing from China.

Advertisement

Gavin Schmidt, the director of NASA’s Goddard Institute for Space Studies, which maintains NASA’s global temperature database, explained the Chinese data glitch:

Still, the fact that NASA and the JMA used different calculation methods to arrive at similar results is telling. Another agency, NOAA, will release its estimate of May global temperatures next Monday using a third method.

The exceptionally warm month was egged on by a building El Niño in the tropical Pacific. Europe, Central Asia, Russia, Japan, Australia, Southern Africa, Brazil, Eastern Canada, and Western North America (so, basically everywhere) were warmer than normal last month. Besides shifting weather patterns worldwide, that extra El Niño-fueled ocean warmth is supercharging the Earth’s temperature, which could help make 2014 the warmest year since human records have been kept, and probably for much longer. El Niño’s effects should peak between October and December and will likely continue into early 2015.

NASA uses a baseline set from 1951-1980 to determine how much a month’s temperature deviates from normal. The agency’s preliminary numbers show the combined global land and ocean temperature during May deviated from that baseline by about three-quarters of a degree Celsius, the most of any May since accurate records began in 1880. The 0.76 degree Celsius anomaly is tied for the sixth-largest anomaly for any month since 1880. All 10 of the biggest monthly temperature anomalies on record have occurred since 1995, according to NASA:

January 2007: 0.93
March 2002: 0.89
March 2010: 0.87
February 1998: 0.86
April 2010: 0.82
October 2005: 0.76
May 2014: 0.76*

February 1995: 0.75
June 1998: 0.75
November 2013: 0.75
*Preliminary

In April, monthly concentrations of carbon dioxide reached 400 parts per million for the first time in at least 800,000 years. On our current path of minimal attention, scientists say warming could exceed 4.5 degrees Celsius by 2100—which would have devastating effects.

Update, June 23, 2014:  On Monday, new NOAA data joined NASA and JMA in declaring that May 2014 was the warmest May on record. The global record was driven primarily by excessively warm ocean temperatures that NOAA ranked as some of the warmest that had ever been measured, "tying with June 1998, October 2003, and July 2009 as the highest departure from average for any month on record."

Last month's warmth continues the recent trend​ of global warming, at least for the month of May, over the last few years. From NOAA:

Four of the five warmest Mays on record have occurred in the past five years: 2010 (second warmest), 2012 (third warmest), 2013 (fifth warmest), and 2014 (warmest); currently, 1998 has the fourth warmest May on record.  

Future Tense is a partnership of SlateNew America, and Arizona State University.

Eric Holthaus is a meteorologist who writes about weather and climate for Slate’s Future Tense. Follow him on Twitter.

TODAY IN SLATE

Politics

Meet the New Bosses

How the Republicans would run the Senate.

The Government Is Giving Millions of Dollars in Electric-Car Subsidies to the Wrong Drivers

Scotland Is Just the Beginning. Expect More Political Earthquakes in Europe.

Cheez-Its. Ritz. Triscuits.

Why all cracker names sound alike.

Friends Was the Last Purely Pleasurable Sitcom

The Eye

This Whimsical Driverless Car Imagines Transportation in 2059

Medical Examiner

Did America Get Fat by Drinking Diet Soda?  

A high-profile study points the finger at artificial sweeteners.

The Afghan Town With a Legitimately Good Tourism Pitch

A Futurama Writer on How the Vietnam War Shaped the Series

  News & Politics
Photography
Sept. 21 2014 11:34 PM People’s Climate March in Photos Hundreds of thousands of marchers took to the streets of NYC in the largest climate rally in history.
  Business
Business Insider
Sept. 20 2014 6:30 AM The Man Making Bill Gates Richer
  Life
Quora
Sept. 20 2014 7:27 AM How Do Plants Grow Aboard the International Space Station?
  Double X
The XX Factor
Sept. 19 2014 4:58 PM Steubenville Gets the Lifetime Treatment (And a Cheerleader Erupts Into Flames)
  Slate Plus
Tv Club
Sept. 21 2014 1:15 PM The Slate Doctor Who Podcast: Episode 5  A spoiler-filled discussion of "Time Heist."
  Arts
Television
Sept. 21 2014 9:00 PM Attractive People Being Funny While Doing Amusing and Sometimes Romantic Things Don’t dismiss it. Friends was a truly great show.
  Technology
Future Tense
Sept. 21 2014 11:38 PM “Welcome to the War of Tomorrow” How Futurama’s writers depicted asymmetrical warfare.
  Health & Science
The Good Word
Sept. 21 2014 11:44 PM Does This Name Make Me Sound High-Fat? Why it just seems so right to call a cracker “Cheez-It.”
  Sports
Sports Nut
Sept. 18 2014 11:42 AM Grandmaster Clash One of the most amazing feats in chess history just happened, and no one noticed.