NASA Analysis: 2021 Tied for 6th Hottest Year in Continued Warming Trend

Earth’s global average surface temperature 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).

Continuing the planet’s long-term warming trend, global temperatures in 2021 were 1.5 degrees Fahrenheit (0.85 degrees Celsius) above the average for NASA’s baseline period, according to scientists at NASA’s Goddard Institute for Space Studies (GISS) in New York. NASA uses the period from 1951-1980 as a baseline to see how global temperature changes over time.

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.

According to NASA’s temperature record, Earth in 2021 was about 1.9 degrees Fahrenheit (or about 1.1 degrees Celsius) warmer than the late 19th century average, the start of the industrial revolution.

“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. NASA’s scientific research about how Earth is changing and getting warmer will guide communities throughout the world, helping humanity confront climate and mitigate its devastating effects.”


2021 was tied for the sixth warmest year on NASA’s record, stretching more than a century. Because the record is global, not every place on Earth experienced the sixth warmest year on record. Some places had record-high temperatures, and we saw record droughts, floods, and fires around the globe. Credit: NASA’s Scientific Visualization Studio/Kathryn Mersmann

This warming trend around the globe is due to human activities that have increased emissions of carbon dioxide and other greenhouse gases into the atmosphere. The planet is already seeing the effects of global warming: Arctic sea ice is declining, sea levels are rising, wildfires are becoming more severe and animal migration patterns are 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.

Weather stations, ships, and ocean buoys around the globe record the temperature at Earth’s surface throughout the year. These ground-based measurements of surface temperature are validated with satellite data from the Atmospheric Infrared Sounder (AIRS) on NASA’s Aqua satellite. Scientists analyze these measurements using computer algorithms to deal with uncertainties in the data and quality control to calculate the global average surface temperature difference for every year. NASA compares that global mean temperature to its baseline period of 1951-1980. That baseline includes climate patterns and unusually hot or cold years due to other factors, ensuring that it encompasses natural variations in Earth’s temperature.

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 degrees Celsius) from what the average would have been.

A separate, independent analysis by NOAA also concluded that the global surface temperature for 2021 was the sixth-highest since record keeping began in 1880. NOAA scientists use much of the same raw temperature data in their analysis and have a different baseline period (1901-2000) and methodology.

“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.”

NASA’s full dataset of global surface temperatures for 2021, as well as details of how NASA scientists conducted the analysis, are publicly available from GISS.

GISS is a NASA laboratory managed by the Earth Sciences Division of the agency’s Goddard Space Flight Center in Greenbelt, Maryland. The laboratory is affiliated with Columbia University’s Earth Institute and School of Engineering and Applied Science in New York.

Climate ChangeGlobal WarmingNASANASA Goddard Space Flight Center
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  • Clyde Spencer

    “Earth’s global average surface temperature in 2021 tied with 2018 as the sixth warmest on record, …”

    That can also be stated as 2021 and 2018 tied for the coolest years in the last 7 years! Whether half a glass of water is half full or half empty depends on what process was in action just prior to making the observation. The global temperatures reached a peak in 2016, and the general trend has been cooling since then.

    “The planet is already seeing the effects of global warming: Arctic sea ice is declining,”
    It currently seems to be increasing from the low reached in 2012.
    “sea levels are rising,”
    Sea levels have been rising for the last 12,000 years.
    “wildfires are becoming more severe”
    Compared to what? The US acreage lost annually was much greater in the early-1900s than in recent years.
    “and animal migration patterns are shifting.”
    Shifting animal migration patterns are the way animals cope with changing climate, whether warming or cooling. Animals have always done that.

    Why is it that these kinds of reports from NASA and NOAA put a negative spin on natural events and try to hide the cooling that has been taking place for the last 7 years? It is not what I would call objective reporting.

  • vealham scorchroad

    What if it turns out that massive electricity use is a primary contributor to global warming? Heat is a natural byproduct of sending electrical current through wires. Is it possible even clean energy won’t save us? Could it be that our addiction to electricity is what will doom our planet, and NOT what we use to make electricity?

    • Clyde Spencer

      Even though ALL the electricity produced will eventually end up as heat, some simple calculations show that the waste energy produced by humans is a small fraction of the energy received by the sun.