A record of 52.9 degrees Celsius (127.2 Fahrenheit) in suburban Delhi on Wednesday – surpassing the national record – was an outlier compared to other stations, and India’s Meteorological Department said it was checking data and sensors.
The incident underscores the importance of verifying temperature readings, especially for monitoring and understanding how the climate is changing – and responding to it.
The United Nations World Meteorological Organization is responsible for entering global, continental and hemispheric temperature records.
The Geneva-based WMO maintains a global archive of weather and climate extremes, which records temperature, pressure, precipitation, hail, aridity, wind, lightning and weather-related mortality.
The lengthy verification process takes months and even years of careful scientific review, and sometimes sees flaws and equipment errors that lead to claimed records.Long evaluation
The WMO first contacts the national weather service of the country concerned, and the organization that takes the necessary records to obtain the raw data. This includes details about the exact reading location, equipment used, calibration, and regional weather conditions at the time.
The initial evaluation was carried out by the WMO Climatology Commission and Randall Cerveny, the organization’s rapporteur for extreme weather and climate, who is the head of the record archive.
An international panel of atmospheric scientists then reviewed the raw data and gave Cerveny, a professor of geography at Arizona State University, a recommendation for the final verdict.
The database was started in 2007
In 2005, while watching US news coverage of Hurricane Katrina’s trail in New Orleans, Cerveny was attacked by a television presenter who repeatedly called the storm the worst hurricane of all time.
He knew something else: while Katrina killed 1,800, a tropical cyclone in 1970 killed an estimated 300,000 people in what is now Bangladesh.
Cerveny co-wrote a scientific article calling for an official global record database.
And in 2007, the WMO asked him to set one, to keep world, hemispherical and regional records for certain extreme weather events.
Measuring climate change
Knowing the prevailing weather and climate extremes is essential to determine exactly how much and how fast the world’s climate is changing, according to the WMO.
The information is also important for health planning and civil engineering. For example, an architect must know the maximum wind speed when designing a bridge.
Another reason to maintain a database of records is to advance science — and to help the media put weather events in perspective.
The all-time heat record was overturned
WMO also re-examines records from before 2007, and sometimes delists.
The most famous case is the world record temperature of 58 C (136 F) measured in 1922 in El Azizia, in what is now Libya.
After a two-year investigation under dangerous conditions during the 2011 Libyan revolution, the recording was invalidated due to five main problems, including potentially problematic instrumentation and “new and inexperienced observers”.
Since then, 56.7 C (134.1 F) registered on July 10, 1913 at Furnace Creek, in Death Valley in the United States, has held the world record for heat.
In July 2021, the WMO recognized a new high temperature record for the Antarctic continent, confirming a reading of 18.3 C (64.9 F) at Argentina’s Esperanza research station on the Antarctic Peninsula on February 6, 2020.
But importantly, the WMO rejected the higher temperature reading of 20.75 C (69.35) reported on February 9, 2020 at Brazil’s automated permafrost monitoring station on nearby Seymour Island.
Finding an improvised radiation shield caused a demonstrable thermal bias error for the permafrost monitor’s air temperature sensor, making the reading ineligible as a record.
