Posted on 14 July 2021 by Guest Author

This is a re-post from Yale Climate Connections by Jeff Masters

For the second consecutive year, Death Valley, California, has set a world record for the hottest reliably measured temperature in Earth’s history.

Death Valley National Park’s Furnace Creek Visitor Center hit an astonishing 130.0 degrees Fahrenheit (54.4°C) on Friday afternoon, July 9, 2021, beating the previous world record of 129.9 degrees Fahrenheit (54.4°C), set there on August 16, 2020. For perspective, according to What’s Cooking America, a medium-rare steak is cooked to an internal temperature of 130-135°F.

According to weather records expert Christopher Burt, who wrote the comprehensive weather records book Extreme Weather, and extreme weather expert Maximiliano Herrera, who tweets under the Twitter handle Extreme Temperatures Around the World, the observation, if confirmed, would be the hottest reliably recorded temperature in world history.

Cautions about the record

Friday’s measurement will have to undergo review by the World Meteorological Organization (WMO) before being declared officially valid. Two possible areas of concern are that the temperatures at Furnace Creek showed a steep jump during the afternoon, and the nearby Stovepipe Wells station was considerably cooler, topping out at 122.6 degrees Fahrenheit (50.3°C). (See the raw high-resolution Furnace Creek data here by choosing a time up to six days in the past from the drop-down menu, then choosing “Decoded Data”.) WMO has not yet certified last year’s 129.9 degrees Fahrenheit (54.4°C) reading on August 16, 2020 at Furnace Creek as valid, so there may be a long wait. Fortunately, we’ll have excellent independent verification of this year’s measurement thanks to a temporary thermometer set up at the site in May by Campbell Scientific.

Climatologist William Reid, an expert on Death Valley meteorology who has written extensively about the site, cautioned that an increase in vegetation and structures built in the vicinity of the Furnace Creek site in recent decades has allowed the station to record hotter temperatures.

“An increase in vegetation and some man-made structures not too far south of the station have resulted in poorer ventilation through the station area. Since the station is above a bare and sandy surface, hot air along the ground during afternoon sunshine is less effectively mixed away from the instrumentation. The result is higher temperature readings during the afternoon comparably,” Reid wrote. “I figure that most summer maximums at Death Valley today are a couple of degrees higher because of the poorer station exposure. A day that hits 125 degrees today probably would have only been as high as 122-123 degrees before 1980.”

Figure 1. Hourly maximum temperature at Death Valley National Park’s Furnace Creek Visitor Center July 6-12, 2021. (Image credit: NOAA)

Official world record remains 134°F at Furnace Creek in 1913

“If Friday’s observation passes an investigation (instrument calibration, etc.) then, yes, this is a new reliably measured global extreme heat record,” Burt wrote by email.

But the observation will not count as an official world record. In 2013, WMO officially decertified the official all-time hottest temperature in world history, a 136.4 degrees Fahrenheit (58.0°C) reading from Al Azizia, Libya, in 1923. (Burt was a member of the WMO team that made the determination.) With the Libya record abandoned, the official world record was given to a 134 degrees Fahrenheit (56.7°C) measurement taken at Death Valley on July 10, 1913.

However, this record has been strongly disputed by Burt, Herrera, and Reid.

“The old Death Valley record from July 1913 is 100% bogus (not just 99.9% such), as are all other temperature readings of 130 degrees Fahrenheit or higher from Africa in the past,” Burt said.

Burt wrote a detailed 2016 blog post at Weather Underground challenging the 1913 record at Death Valley, explaining that official readings of 134, 130, and 131 degrees Fahrenheit taken on July 10, 12, and 13, 1913 were likely the result of an inexperienced observer. Climatologist William Reid has also extensively researched what he calls an “improbable record” in 1913. In order for the 1913 Death Valley record to be decertified, though, an official WMO investigation committee would have to be assembled to look into the matter, a years-long process for which there is currently no motivation.

The only other temperature of at least 130 degrees Fahrenheit officially recognized by WMO is a 131-degree reading at Kebili, Tunisia, set July 7, 1931, which is considered to be Africa’s hottest temperature.

Burt disputed this record: “I mentioned to the WMO about the Kebili temperature of 131 degrees Fahrenheit back in 2012, when asked what I thought the next hottest temperature in Africa (after Al Azzia) might be, since that was the only temperature over 130 degrees Fahrenheit that had an actual date attached to it. However, the Kebili ‘record’ is even more bogus than even the Al Azzia record, and I said so. Kebili is a relatively cool spot in Tunisia (an oasis) and never since the 1930s ever again recorded a maximum temperature above 118 degrees Fahrenheit. Nowhere in Africa has any reliably observed temperature been measured above 126 degrees Fahrenheit.”

Figure 2. The unofficial thermometer at Death Valley National Park’s Furnace Creek Visitor Center (which reads about 5°F too high, compared to the official instrument), as seen on Saturday afternoon, July 10, 2021. Earth’s third-hottest reliably measured temperature in history, 54.1° C (129.4°F), was recorded that day at the site. (Image credit: William Reid)

Top-10 list of hottest world temperatures: Furnace Creek dominates

Furnace Creek made a run at beating its Friday world record on Saturday, but according to an email from climatologist William Reid, who visited Death Valley that day, high clouds moved over the station in the afternoon, allowing the temperature to reach “only” 129.4 degrees Fahrenheit (54.1°C). Even so, the highs Friday and Saturday mean that the planet’s top three hottest reliably measured temperatures on record have all occurred at Furnace Creek in the past year. Here’s is Earth’s top-ten list of hottest reliably measured temperatures:

1) 54.4° C (130.0°F), 7/09/2021, Furnace Creek (California, U.S.); 
2) 54.4° C (129.9°F), 8/16/2020, Furnace Creek (California, U.S.); 
3) 54.1° C (129.4°F), 7/10/2021, Furnace Creek (California, U.S.);
4) 54.0° C (129.2°F), 6/30/2013, Furnace Creek (California, U.S.);
4) 54.0° C (129.2°F), 7/21/2016, Mitribah (Kuwait);
6) 53.9° C (129.0°F), 7/17/1998, Furnace Creek (California, U.S.);
6) 53.9° C (129.0°F), 7/19/2005, Furnace Creek (California, U.S.);
6) 53.9° C (129.0°F), 7/06/2007, Furnace Creek (California, U.S.);
6) 53.9° C (129.0°F), 7/22/2016, Basra International Airport (Iraq); and
10) 53.8° C (128.8°F), 7/22/2016, Basra-Hussen (Iraq).

Kudos go to Maximiliano Herrera (@extremetemps) and Jérôme Reynaud (geoclimat.org) for helping assemble this list.

Figure 3. The Stovepipe Wells measurement station in Death Valley, California. (Image credit: NOAA)

Highest recorded minimum temperature in North America: 107.7°F

Another astonishing heat record occurred on Sunday, when the 24-hour low temperature at Stovepipe Wells, also located in Death Valley, dropped to a ridiculously hot 107.7 degrees Fahrenheit (42.1°C). The previous North American hottest reliably measured minimum temperature on record was 107 degrees Fahrenheit (41.7°C) at Furnace Creek on July 12, 2012. On Sunday, the high temperature at Stovepipe Wells hit 128.6 degrees Fahrenheit (53.7°C) – one of the hottest U.S. temperatures ever measured. Summing together Sunday’s high and low and dividing by two gives an average temperature for the day of 118.1 degrees Fahrenheit (47.8°C), which is very likely a world record for reliably measured average daily temperature.

According to weather records expert Maximiliano Herrera (@extremetemps), only one location worldwide has recorded a higher overnight minimum temperature than Stovepipe Wells: Oman. The world record for highest 24-hour minimum temperature is 108.7 degrees Fahrenheit (42.6°C) at Qurayyat, Oman, on June 26, 2018. The world record for highest overnight low (12-hour low) is 111.6 degrees Fahrenheit (44.2°C) at Khasab Airport, Oman, on June 17, 2017.

Note that the Western Region Climate Center shows seven daily minimums of 110°F occurred at Death Valley’s Greenland Ranch, primarily in the 1920s. These would be the official hottest minimums on record for the world, presumably. However, in an email, climatologist William Reid said, “Do I believe they are authentic? No. The record provided by the observer is plagued by some of the problems found during the 1913 era at the site”.

Stovepipe Wells, established in 2004, is part of NOAA’s Climate Reference Network, with equipment among the highest quality in the world. The station is located at an elevation of 80 feet (24 m), and is usually 3-5 degrees Fahrenheit cooler than Furnace Creek, which is at -193 feet (-59 m).

Other all-time heat records July 9-11

Among U.S. stations with long periods of record spanning at least 40 years, there were at least 12 sites that tied or exceeded their previous all-time (any day) heat record during the July 9-11 western U.S. heat wave (kudos to Maximiliano Herrera for this list):

July 9:
Grand Junction, CO: 107°F (41.7°C), new record
Tonopah, NV: 104°F (40.0°C), tied

July 10:
St. George, UT: 117°F (47.2°C), ties all-time state record for Utah
Farmington, NM: 106°F (41.1°C), new record
St. Johns, AZ: 104°F (40.0°C), tied
Page, AZ: 111°F (43.9°C), tied
Mercury, NV: 113°F (45.0°C), tied
Toponah, NV: 104°F (40.0°C), tied
Las Vegas Airport, NV: 117°F (47.2°C), tied
China Lake, CA: 119°F (48.3°C), tied
Barstow-Daggett Airport, CA: 118°F (47.8°C), tied
Bishop, CA: 111°F (43.9°C), new record
Winslow, AZ: 110°F (43.3°C), new record

July 11:
Tonopah, NV: 105°F (40.6°C), new record

This list may be updated if additional records come to light, or are set on Monday, when the heat wave will be winding down. Over the past 30 days, according to the NOAA/NCEI database of record highs and lows, the U.S. has racked up a startling total of at least 301 all-time record highs. NOAA’s list includes stations with a period of record shorter than 40 years, though.

Update from July 13: Many more all-time heat records fell July 9-11 in Utah, Arizona, California, Colorado, and Nevada, according to Maximiliano Herrera. In Utah alone, there were these: Eskdale (tied), Kodachrome Basin (tied), Fort Duchesne (tied), Hovenweep 109°F on July 9 (beaten),  Escalante 106°F on July 9 (beaten), and Bullfrog Basin 114°F on July  10 (beaten).

Figure 4. Predicted height of the atmosphere’s 500-mb surface in decameters (dm) at 18Z (2 p.m. EDT) Tuesday, July 20, 2021, according to the 0Z Monday, July 12, run of the European model. A near record-strength ridge of high pressure with a 500 mb height peaking at 599 dm was predicted to be centered over Wyoming. (Image credit: weathermodels.com)

Déjà vu: another extreme high-pressure ridge predicted for the western U.S. next week

It’s July, the hottest month of the year in the Northern Hemisphere, and extreme ridges of high pressure forming in July have a good chance of setting all-time heat records. Unfortunately, the latest long-range forecasts from the GFS and European models predict that the western U.S. will have another unusually intense ridge of high pressure capable of overthrowing more all-time U.S. heat records next week.

By one common measure, the 0Z Monday run of the European model is predicting that the heat dome at the center of this upper-level high will be nearly as strong as any ever observed in the region. Warm air expanding at lower levels pushes the height of the 500-millibar surface, roughly at the midpoint of the atmosphere, upward. The model predicted a 500-mb height of 599 decameters over Wyoming on July 20. The record-high 500-millibar height at Riverton, Wyoming, as measured in twice-daily weather-balloon launches (soundings) since 1948, is 605 dm.

But long-range forecasts of this nature are often inaccurate, so the coming heat wave may fall short of setting all-time records. However, the models did an excellent job seven days in advance in predicting the intensity of this past weekend’s extreme ridge of high pressure. Even if the next heat wave falls short of setting all-time records, it will boost the odds of significant wildfire activity, and intensify the record drought gripping the western U.S., where severe to exceptional drought (levels D2 to D4) was at 83% last week – the highest level since the U.S. Drought Monitor was established in 2000.