Why is 2023 so hot?

As the world swelters through record temperatures, scientists say an unusual culprit may be partly to blame: an underwater volcanic eruption off Tonga in the South Pacific last year.
While most big blasts cool the planet with a sun-dimming haze, the eruption of Hunga Tonga-Hunga Ha’apai in January 2022 blew the equivalent of 60,000 Olympic swimming pools of water into the stratosphere, high above the planet.
Water vapour is a natural greenhouse gas, trapping heat as it swirls around the globe. By contrast, major land eruptions – such as Pinatubo in the Philippines in 1991 – temporarily dim sunshine with an ashen sunshade before falling back to Earth.
The June-August period this year was the warmest on record worldwide by a puzzlingly wide margin, with heatwaves occurring from Japan to the United States.
Many scientists say more research into volcanoes is vital to gauge how far eruptions can briefly affect the long-term trend of global warming, driven by burning fossil fuels.