2021 tied for Earth’s sixth warmest year on record: NASA Report

The global average surface temperature of the Earth in 2021 tied with 2018 as the sixth warmest on record, according to independent analyses done by NASA and the National Oceanic and Atmospheric Administration (NOAA).

Collective warming

As the planet’s long-term warming trend continues, global temperatures in 2021 were 1.5 degrees Fahrenheit (0.85 °C) more than the average for NASA’s baseline period — 1951 to 1980 — according to scientists at NASA’s Goddard Institute for Space Studies (GISS) in New York.

“Collectively, the past eight years are the warmest years since modern recordkeeping began in 1880. This annual temperature data makes up the global temperature record — which tells scientists the planet is warming,” NASA said in an official release.

According to temperature records kept by the space agency, Earth’s temperature in 2021 was about 1.9 degrees Fahrenheit (or about 1.1 °C) warmer than the late 19^th century average, the start of the industrial revolution.

‘Existential threat’

“Science leaves no room for doubt: Climate change is the existential threat of our time,” said NASA Administrator Bill Nelson. 

“Eight of the top 10 warmest years on our planet occurred in the last decade, an indisputable fact that underscores the need for bold action to safeguard the future of our country — and all of humanity,” added Nelson.

The warming trend across the globe is owing to human activities that have led to increased emissions of carbon dioxide and other greenhouse gases into the atmosphere.

The effect of global warming has been visible with Arctic sea ice declining, rising sea levels, wildfires increasingly becoming more severe and animal migration patterns shifting. 

“Understanding how the planet is changing – and how rapidly that change occurs – is crucial for humanity to prepare for and adapt to a warmer world,” NASA said.

Accounting for uncertainties

Ground-based measurements of surface temperature recorded by weather stations, ships, and ocean buoys around the globe are validated with satellite data from the Atmospheric Infrared Sounder (AIRS) on NASA’s Aqua satellite. These measurements are then analysed by scientists using computer algorithms to navigate uncertainties in the data and quality control to calculate the global average surface temperature differences for each year. 

NASA compares that global mean temperature to its baseline period of 1951-1980. This baseline includes climate patterns and unusually hot or cold years due to other factors.

“Many factors affect the average temperature any given year, such as La Nina and El Nino climate patterns in the tropical Pacific. For example, 2021 was a La Nina year and NASA scientists estimate that it may have cooled global temperatures by about 0.06 degrees Fahrenheit (0.03 °C) from what the average would have been,” it explained.

Similar trends

The conclusion of global surface temperature for 2021 being the sixth highest since record keeping began in 1880 was also supported by an independent analysis by NOAA.

“NOAA scientists use much of the same raw temperature data in their analysis and have a different baseline period (1901-2000) and methodology,” it explained.

“The complexity of the various analyses doesn’t matter because the signals are so strong,” said Gavin Schmidt, Director of GISS, NASA’s leading center for climate modeling and climate change research. 

“The trends are all the same because the trends are so large,” Schmidt said.

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