In Short : Scientists have long known that temperatures will continue to rise as humans keep releasing record amounts of planet-heating greenhouse gases like carbon dioxide, mainly through burning fossil fuels. This is the main cause of global warming.
In Detail : There have been historically high sea temperatures, worrying lows in Antarctic sea-ice, and extreme weather events hitting every continent – the latest being an “unbearable” heatwave in Brazil.
It’s now “virtually certain” that 2023 will be the hottest year on record. That’s something that no major climate science body expected at the start of the year.
Scientists have long known that temperatures will continue to rise as humans keep releasing record amounts of planet-heating greenhouse gases like carbon dioxide, mainly through burning fossil fuels. This is the main cause of global warming.
While they are struggling to fully explain 2023’s “gobsmacking” surge in temperatures, here are four additional reasons that could be behind the increases.
A ‘weird’ El Niño
One key factor is the unusually rapid onset of a natural weather system known as El Niño.
During an El Niño, warmer surface waters in the eastern Pacific release additional heat into the atmosphere. This typically leads to a surge in global air temperatures.
The graph below shows how a new El Niño is strengthening. It has not yet reached the peak of the last major one in 2016, as you can see, but is expected to intensify in the coming months.
The ongoing 2023 El Niño may be releasing even more warmth than previous ones, because the world had previously been in an extended cool phase – an opposite weather system known as La Niña.
This kept a lid on global temperatures for an unusually long period, as warmth was less able to escape from the sea surface into the atmosphere.
During this time, the oceans continued to absorb record amounts of heat, some of which is now finally being released into the atmosphere.
Normally, scientists expect a delay of around three months between maximum El Niño strength and global air temperatures peaking, explains Zeke Hausfather, a climate scientist at Berkeley Earth, a science organisation in the US.
But air temperatures have risen much more quickly during this El Niño than with previous ones, and it’s not even reached full strength yet.
As Dr Hausfather puts it, “this El Niño is weird.”