Scientists unnerved by record shattering 2023 temperatures
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Climate scientists lack an explanation for why 2023 was the world's hottest year by such a large margin, calling the records revealed Friday "astonishing."
Why it matters: Without an adequate explanation for 2023's record global temperatures, scientists could be missing a shift in the climate system that would call into question their projections of future climate change.
Driving the news: NOAA, NASA and the independent climate tracking group Berkeley Earth released new annual temperature data on Friday.
- Each group's data, calculated using slightly different sources and methods, showed the year was by far the hottest on record globally, which defied expectations from earlier in the year.
Zoom in: The record-breaking heat extended from the air to the sea, NOAA found, as the amount of heat stored in the top 2,000 meters of the ocean shattered records as well.
- The oceans store about 90% of the heat in the climate system, making them a critical climate indicator.
- According to NOAA, 2023 ranks as the hottest year since their instrument data began in 1850, beating out the previous record-holder of 2016 by a record-setting margin of 0.27°F.
- The 10 warmest years in NOAA's database have each occurred in the past 10 years.
The intrigue: Typically, climate scientists hold a press conference at the end of a year to explain where the period ranked on the list of hottest years and why.
- This year, NOAA and NASA's top climate researchers could only accomplish the first part, saying it is not yet known why the year got so unusually warm.
- "We're looking at this and we're frankly, astonished," Gavin Schmidt, who heads NASA's Goddard Institute for Space Studies in New York City, said during a press conference.
Between the lines: The factors that scientists are investigating as potential causes for 2023's rapid warming include the quick flip from a robust, long-lasting La Niña to a strong El Niño.
- However, temperatures didn't warm in lockstep with previous El Niño events, since usually such events have a three-month delay on global temperatures.
- There has also been a drop in certain emissions from marine shipping, and water vapor in the stratosphere as a result of 2022's explosive eruption of the Hunga Tonga-Hunga Ha'apai undersea volcano in the South Pacific.
Context: A recent study casts doubts on the warming effects of the Hunga Tonga eruption.
- Schmidt said 2024's conditions will help indicate whether 2023 was just "a blip" or if "There's something systematically different going forward."
- "I think we're discomforted by the findings that we've had," Schmidt said.
Yes, but: Some climate scientists, most prominently former NASA researcher James Hansen, have already concluded that last year was not just a blip, and climate change is speeding up due to the planet's increasingly lopsided energy imbalance.
- This is caused by the increasing amounts of greenhouse gases in the atmosphere, which absorb heat and were emitted by burning fossil fuels.
- Most climate scientists have not yet bought into Hansen's conclusions, but many have not ruled it out, either.
The bottom line: As climate scientist Zeke Hausfather wrote Friday, predictions for 2024's temperatures are now less reliable after the notable forecast bust for 2023.
- "Ultimately, what matters for the climate is not the leaderboard of individual years," Hausfather wrote Friday. "Rather, it is the long-term upward trend in global temperatures driven by human emissions of greenhouse gases. Until the world reduces emissions down to net-zero, the planet will continue to warm."
Go deeper: The world's hottest year may soon be an average one
