2023 has been confirmed as the warmest ever experienced by humankind, as a result of climate change and the natural El Niño weather event – propelling the world to just hundredths of a degree away from a critical climate threshold.
During 2023 temperatures were 1.48C warmer than the long-term average before humans started burning large amounts of fossil fuels, according to the EU’s Copernicus Climate Change Service (C3S).
Samantha Burgess, Deputy Director of C3S, describes it as an ‘exceptional year’, breaking climate records. She said that all days in 2023 were over 1°C warmer than during the pre-industrial period.
Scientists estimate last year’s temperatures most likely exceeded any period in the last 100,000 years – a date reached by analysis of sediment from the seabed – and roughly 90,000 years before humans settled into communities and started farming.
Almost every day from July saw a new global air temperature high for the time of year, while sea surface temperatures have also been higher than ever before.
2023 Surpasses Predictions
These global records are bringing the world closer to breaching the key international climate target of a 1.5C increase.
‘What struck me was not just that  was record-breaking, but the amount by which it broke previous records,’ said Andrew Dessler, a professor of atmospheric science at Texas A&M University.
It is an accepted scientific fact that the world is much warmer now than 100 years ago, as humans keep releasing record amounts of greenhouse gases like carbon dioxide into the atmosphere.
However 12 months ago, scientists were not predicting record heat levels because of the unpredictable way in which the Earth’s climate behaves. And during the first few months of the year, only a small number of days broke air temperature records.
But the world saw an almost unbroken streak of new daily records in the second half of 2023 as more than 200 days saw a new daily global temperature high for the time of year, according to the C3S.
Researchers linked the increases to the rapid switch to El Niño conditions, where warmer surface waters in the East Pacific Ocean release additional heat into the atmosphere, on top of long-term human-caused global warming.
But air temperatures have been boosted unusually early on in this El Niño phase – the full effects had not been expected until early this year.
‘That raises a bunch of really interesting questions of why [2023 was] so warm,’ said Zeke Hausfather, a climate scientist at US research establishment Berkeley Earth.
Almost all of the world experienced above average temperatures, especially northern Canada, parts of the Arctic and Antarctic, and western South America.
Also Antarctic sea-ice hit an extreme low, with Arctic sea-ice also below average, while glaciers in western North America and the European Alps experienced an extreme melt season, adding to sea-level rise.
The heat worsened many extreme weather events across large parts of the world in 2023 – from intense heatwaves and wildfires across southern Europe, Canada and the US, to prolonged drought and then flooding in parts of east Africa.
‘These are more than just statistics,’ said Prof Petteri Taalas, Secretary General of the World Meteorological Organization up until last year. ‘Extreme weather is destroying lives and livelihoods on a daily basis.’
The year 2024 could be warmer than 2023 and may even surpass the key 1.5C warming threshold across the entire calendar year for the first time, according to the UK Met Office.
Nearly 200 countries agreed in Paris in 2015 to try to limit warming to this level, to avoid the worst effects of global warming. It refers to long-term averages over 20 or 30 years, so a year-long breach in 2024 wouldn’t mean the Paris agreement had been broken.
However such an event would create alarm, with each hot year bringing the world closer to passing 1.5C over the longer term.