Sometimes a vast warm current appears in the Pacific Ocean, changing weather across the globe. This is El Niño. When it is particularly strong, strange things happen: carbon dioxide levels in the air rise, and Earth itself starts spinning a little faster. For a long time, scientists could only guess that these events were connected.

Now researchers have compared records spanning several decades: the strength of El Niño (measured by six ocean indicators), carbon dioxide levels in Hawaii, and the length of the day (which fluctuates slightly around 24 hours). It turns out that after a strong El Niño, CO2 growth accelerates three months later, and Earth's rotation four months later. The relationship is as regular as clockwork: the stronger the current, the more noticeable the effect.

But in 1991, Mount Pinatubo in the Philippines erupted so much ash that the link was disrupted for two years. This shows that under normal conditions, the rhythm holds. Now scientists can test their models: if a model reproduces these numbers, it correctly captures how the ocean, the atmosphere, and Earth's rotation are interconnected.