Is another factor beyond global warming leading to this summer's record temperatures?

Around the world, temperature records have shattered this summer, and scientists now wonder if something beyond global warming is at work.

Researchers have suggested that a reduction in sunlight-reflecting particles from shipping – or an undersea volcanic eruption – could also be contributing to this summer's soaring heat.

July was a third of a degree Celsius hotter than previous records and in June, the global-mean surface air temperature was more than 1.5C above pre-industrial levels in early June, is a first for a summer month, according to the Copernicus Climate Change Service (C3S).

Global temperatures higher than 1.5C above pre-industrial levels have been observed before, but until now only in the northern hemisphere winter and spring months.

The biggest cause is man-made climate change, combined with a warming El Niño weather cycle, but scientists now suspect a third factor may be in operation – relating to particles in the atmosphere.

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Scientists agree that man-made climate change is the main culprit, along with a natural El Nino.

El Niño events see the Pacific up to 3C warmer than normal, and during La Niña – the other part of the cycle – the ocean is up to 3C colder.

Several experts have warned that this year’s El Niño could see the crucial 1.5C temperature barrier (compared to pre-industrial levels) breached as global temperatures soar.

Copernicus director Carlo Buontempo observed, "What we are seeing is more than just El Niño on top of climate change."

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Cleaner air from new maritime shipping rules introduced in recent years may be contributing to Earth's rising temperatures, some scientists believe.

International regulations which took effect in 2020 slashed emissions of sunlight-reflecting particles from oceangoing vessels by up to 80%.

This reduction in atmospheric pollutants could be removing a source of cooling that has partially masked the climate impacts of greenhouse gases.

Researchers are also investigating whether 165 million tons of water vapour ejected by Hunga Tonga-Hunga Ha'apai undersea volcano in the South Pacific in January may be trapping additional heat.