Climate change is by far the main cause of this summer's sweltering heat, but the eruption of the Hunga Tonga-Hunga Ha-apai undersea volcano in 2022, changes in the amount of energy emitted by the sun, and the Pacific Ocean heading into its warmer El Niño phase are other factors helping push the mercury to new extremes.

The eruption of the Hunga Tonga-Hunga Ha-apai volcano has vaporized large amounts of seawater, which could raise global temperatures by 0.06 degrees F (more than 0.03 degrees C) over the next few years, according to a recent study.

The amount of energy emitted from the sun rises and falls slightly every 11 years. At the peak of this cycle, a surge in solar energy warms the Earth by about 0.09 degrees F (0.05 degrees C). The sun is now rising to its next peak, expected in 2025.

The Pacific Ocean is heading into its warmer El Niño phase, when warm ocean waters radiate heat into the air. The last strong El Niño raised global temperatures by 0.25 degrees F (0.14 degrees C).

Climate change is still much bigger than any of these factors. Humans have warmed the Earth by 2.2 degrees F (1.2 degrees C) since the pre-industrial era, setting the stage for a depressingly hot weather. Scientists say climate change made the recent heat wave in China 50 times more likely, while concurrent heat waves in Europe and North America were at least 1,000 times more likely. This month is on track to be the hottest on record, with unprecedented heat signaling that “an era of global boiling has arrived,” said UN Secretary-General António Guterres.

And temperatures are still rising. “If a strong El Niño develops over the next year, combined with a solar maximum and the effects of the Hung Tonga-Hunga Ha’apai eruption, Earth’s temperatures would likely soar to unprecedented heights,” Michael Wysession, an Earth scientist at the University of Washington, wrote in The Conversation. “According to climate modeling, this would likely mean even more heat waves, wildfires, flash floods, and other extreme weather events.” (AI)