Scientists have found that oceans continued getting warmer in 2025, leading to adverse climate conditions across the globe. This includes New Zealand, which has experienced an alarming amount of rainfall over the last year. 

What's happening?

In a study published in the journal Advances in Atmospheric Sciences, a team of researchers revealed that the world's oceans reached a new, record-high heat content for the ninth consecutive year in 2025. In total, they absorbed approximately 23 zettajoules more energy than in 2024.

These unusually warm ocean waters are linked to an increase in evaporation and moisture in the atmosphere. In turn, this can create intense, heavy rainfall that triggers flooding across countries such as New Zealand.

Kevin Trenberth, a distinguished scholar at the National Center for Atmospheric Research and co-author of the study, penned an article on The Conversation to detail the team's findings.

"Understanding ocean heat — and how it shapes rainfall, storms, and marine heatwaves — is central to explaining what we experience on land," he wrote.

Why are warmer ocean temperatures important?

According to Trenberth, the continued warming indicates that oceans are absorbing over 90% of the excess heat from human-caused pollution. Ocean depths up to 2,000 meters have shown massive heat accumulation, contributing significantly to intensified extreme weather. 

"This is not a passive process," Trenberth explained. "Heat entering the ocean raises sea surface temperatures, which in turn influence exchanges of heat and moisture with the atmosphere and change weather systems." 

While the added heat can create "atmospheric rivers" that dump heavy rain on already saturated ground, Trenberth noted that it can also increase the risk of droughts and wildfires in other regions. 

Another side effect of high ocean temperatures is the threat of sea level rise. As water heats up, it expands. When combined with the immense volume of the ocean during El Niño events, it can lead to a significant increase in water levels. This can also raise the risks of flooding and devastating storm surges for coastal communities.

Whether through increased rainfall or prolonged droughts, high ocean temperatures can lead to the displacement of thousands of people and the disruption of vital industries. 

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What's being done about rising ocean temperatures?

As Trenberth noted, keeping a close eye on ocean temperatures will play a pivotal role in determining forecasts and developing mitigation efforts. 

"Monitoring sea-level rise through satellite altimetry is therefore an essential complement to tracking ocean heat content," he added. "Tracking both heat and water is crucial to understanding variability and long-term trends."

For now, many countries around the globe are attempting to get a better handle on their air pollution contributions. Initiatives such as the Paris Agreement have been put in place to help reduce reliance on natural gas, coal, and oil and instead promote more sustainable energy resources such as wind and solar power.

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