Scientists believe that the unusually hot year is part a long-term warming trend, which shows signs of acceleration.
On Thursday, two U.S. science agencies, NASA and the National Oceanic and Atmospheric Administration, and a private measurement group released their calculations of last year's global temperatures. All said that it was not far behind ultra-hot 2016 and 2020.
Six different calculations showed that 2021 was the fifth to seventh hottest since the late 1800s. NASA ranked 2021 sixth in terms of temperature, with 2018 tied at sixth. NOAA placed last year sixth, just ahead of 2018.
Scientists believe that a La Nina, which is a natural cooling process in the central Pacific that alters weather patterns and brings cold deep ocean water to surface, has dampened global temperatures, just like its opposite, El Nino, did in 2016.
They said that 2021 was the hottest La Nina Year on record. This year also did not reflect a cooling of human-caused climate changes but instead provided more heat.
"So it's still not as headline-dominating than being the warmest ever recorded, but we'll see another one in a few years," said Zeke Hausfather, climate scientist at Berkeley Earth, which also ranked 2021 as the sixth hottest. It's the long-term trend and it's an indomitable marche upward.
Gavin Schmidt (climate scientist at NASA) said that "the long-term trend in temperature is very, very clear." It's all because of us. It won't stop until we reduce the amount of carbon dioxide in our atmosphere.
NASA and NOAA data confirm that the last eight years were the hottest ever recorded. Their data shows that global temperatures are almost 2 degrees (1.1 Celsius) warmer today than they were 140 years ago.
Other 2021 measurements were taken by the Japanese Meteorological Agency, Copernicus Climate Change Service i n Europe, and satellite measurements from the University of Alabama in Huntsville.
Scientists have begun to investigate whether temperatures are rising faster than they did eight-ten years ago. Schmidt and Hausfather both said that early signs suggest this, but it's difficult to be certain.
Schmidt stated in an interview that he believes you can see the acceleration but it isn't clear if it is statistically robust. If you look at the past 10 years, how many are significantly above the trend line compared to the 10 years before? They are almost all.
According to NOAA, the global average temperature was 58.5 degrees (14.7 Celsius) last year. NASA's former chief climate scientist James Hansen made headlines in 1988 when he testified before Congress about global warming. This was in 1988, the year that was the hottest ever recorded. The 28th hottest year is 1988, which was 57.7 degrees (14.3 Celsius).
According to Berkeley Earth, last year, 1.8bn people lived in 25 Asian, African, and Middle Eastern countries. These included China, Nigeria and Bangladesh.
According to a separate study, the deep ocean, which is where most heat is stored, set a new record for warmth in 2021.
"Ocean warming is causing coral bleaching, threatening fish populations, and is destabilizing Antarctic Ice shelves and threatens massive... sea level rise, if we don’t act," stated Michael Mann, a Pennsylvania State University climate scientist.
1976 was the last year Earth experienced a less than normal year according to NASA or NOAA calculations. Based on data from the United Nations, this means that 69% of Earth's population -- which is more than 5 billion people below age 45 -- has never seen such a year.
Kathie Dello (39), a North Carolina state climatologist, was not part of the new reports, but said that they make sense. She said, "I have only lived in a warmer world and I wish that younger generations didn't have to feel the same." It didn't have be this way.