Analyses last year had already confirmed 2023 to be the warmest on record, but Tuesday’s data shows an alarming leap in heating from 2016, previously the hottest year. In 2023, the average global temperature was 14.98 degrees Celsius — 0.17 degrees above the previous record — while warming in the world’s oceans also hit a new high.
Scientists repeatedly expressed shock in 2023 as successive heat records fell, and warned the world is moving dangerously close to the 1.5-degree limit that nearly 200 countries sought to avoid in the Paris Agreement in 2015.
The data and an analysis, published by Copernicus — the EU’s climate and weather monitoring agency — says that global warming may worsen at the start of this year, projecting that a 12-month period ending in January or February will likely breach 1.5 degrees.
But scientists are far more concerned about a long-term state of warming of 1.5 degrees and above — rather than individual years. Above that threshold, many of the Earth’s ecosystems will struggle to adapt and summertime heat will approach the limits of human survivability in some places.
The unprecedented heat in 2023 was caused primarily by climate change, Copernicus said, but was exacerbated by El Niño, a natural climate variability that increases Pacific Ocean heat and typically boosts the world’s temperatures.
While some scientists have said the 1.48 degrees of warming is in line with last year’s heat records, others are still surprised at how much hotter 2023 was over previous years.
“It is a shock that this year has unarguably smashed the global temperature record,” said Bill Collins, professor of climate processes at the University of Reading in the UK. “There is no opportunity here to quibble about hundredths of a degree, exceeding the previous record by 0.17 degrees should be an alarm call to everyone.”
Every day in 2023, the global average temperature was at least 1 degree hotter than the corresponding day in the 1850-1900 pre-industrial period, Copernicus said. That’s the first time on record that’s happened.
Global temperatures have been steadily increasing since the 1970s, until 1 degree of global warming was breached for the first time in 2015, according to historical temperature data from Copernicus. It took only eight years to leap another half a degree above pre-industrial levels.
Even compared to the past three decades, when temperatures have been warmer, 2023 stands out. The year was 0.6 degrees Celsius hotter than the 1991-2020 average.
Temperatures rising ‘more exponentially’
Several months ago, there was a projection among the scientific community that warming would hit around 1.3 degrees in 2023, said Liz Bentley, chief executive of the UK’s Royal Meteorological Society. That prediction has been “annihilated,” she said, as temperature records fell on the regional, national and international levels around the world, including daily and monthly records.
Other thresholds are being crossed too — two days in November were, for the first time, more than 2 degrees warmer. Every month in 2023 between June and December was the hottest such month on record. July and August were the first and second-warmest on record, overall, Copernicus said.
Given the tumbling records, Bentley said, it wasn’t so much the 1.48-degree temperature rise that was surprising but the pace of climate change in recent years.
“If you look at climate projections, when we expect to see temperature changes of close to 1.5 degrees Celsius, indeed it has come sooner than many would have expected,” Bentley told CNN. “We’ve definitely seen an acceleration towards that, rather than it being a kind of linear progression. It feels like it’s rising much more exponentially.”
Annual average air temperatures were either the hottest, or nearly the hottest, on record over all ocean basins and all continents, except Australia, the Copernicus data shows. That temperature rise covers nearly the entire world map.
The year of record heat, which saw deadly extreme weather events, including wildfires in Canada, Hawaii and southern Europe, “has given us a taste of the climate extremes that occur near the Paris targets,” said Brian Hoskins, chair of the Grantham Institute, Imperial College London.
“It should shake the complacency displayed in the actions by most governments around the world,” he said.
The world’s oceans also experienced unprecedented heat and remained unusually warm in 2023. Sea surface temperatures were 0.44 degrees above the 1991–2020 average, the highest on record and a leap from the 0.26-degree rise seen in 2016, the second-warmest year.
The main long-term factor behind the oceans’ alarming heat is fossil fuel pollution, but El Niño — which began in July — also contributed. Higher sea surface temperatures can lead to more powerful hurricanes, typhoons and tropical cyclones.
At the tail end of the hottest year on record, nearly 200 countries represented at the COP28 climate talks in Dubai last month agreed for the first time to contribute to a global transition away from fossil fuels, the main cause of the climate crisis. The deal was widely welcomed, but critics say it included loopholes that would allow major fossil fuel producing nations to take little action.
“The extremes we have observed over the last few months provide a dramatic testimony of how far we now are from the climate in which our civilization developed,” said Carlo Buontempo, director of Copernicus’ Climate Change Service. “This has profound consequences for the Paris Agreement and all human endeavors. If we want to successfully manage our climate risk portfolio, we need to urgently decarbonize our economy whilst using climate data and knowledge to prepare for the future.”
