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After record temperatures throughout the second half of the year, 2023 is ‘virtually certain’ to be the hottest year ever recorded.

Despite early predictions of record temperatures, the margin by which records have been broken has taken scientists by surprise. September, for example, saw average temperatures 1.8C higher than pre-industrial levels, 0.5C higher than the previous record. In a world where temperature records are typically broken by 0.1C or 0.2C, this is unprecedented. But September was no outlier – across the first nine months of the year, one in three days were 1.5C or more above pre-industrial levels. Indeed scientists now believe the average temperature for 2023 as a whole is likely to be above 1.5C

This does not mean the world has breached the Paris threshold of keeping temperatures below 1.5C above pre-industrial levels – to do so would require the threshold to be breached consistently for many years. But it highlights just how quickly temperatures are rising – by an unprecedented rate of more than 0.2C over the past decade – and how little time is left to contain them. Indeed latest estimates suggest the world will have emitted enough CO2 to breach the Paris threshold in just six years.

Massive variations

Record temperatures were recorded across the world – September was the hottest on record in Africa, Europe, North and South America, and Antarctica, while sea surface temperatures have been at record highs since April. But these averages hide wild variations – in July, some parts of northern Canada were more than 7C above the 30-year average. 

This extreme heat coming on top of longer-term warming led to devastating consequences in the form of widespread wildfires. These are a good example of what scientists call feedback loops – fires release huge amounts of CO2 that speeds up warming, making wildfires ever more likely, and so the cycle continues.

Compounding events

There are a number of factors that have driven temperatures dramatically higher this year, some of which are unrelated to human-caused climate change.

These include El Niño, a natural climate event occurring every two to seven years that increases sea temperatures in the Pacific Ocean; an undersea volcano erupting last year that increased the amount of water vapour in the atmosphere, trapping heat; and regulations that have reduced the amount of sulphur, which reflects heat back into the atmosphere, emitted by ships.

However, it is abundantly clear that global warming, caused primarily by burning fossil fuels, is driving the dramatic increases in temperatures, and that natural events and variability have had very  little impact