Ocean warming 4 times faster than in 1980s — and likely to accelerate in coming decades

Earth's oceans are getting warmer at an accelerating rate, researchers find — indicating that climate change is speeding up too.

The scientists found that ocean warming has more than quadrupled over the past 40 years and is likely to accelerate even faster in the future. The researchers published their findings in a new study published Tuesday (Jan. 28) in the journal Environmental Research Letters.

The rate of sea surface temperature warming has risen from 0.1 degrees Fahrenheit (0.06 degrees Celsius) per decade in the 1980s to 0.5 F (0.27 C) per decade today. The team's modeling suggests that this amount of accelerated warming will occur again in the next two decades and accelerate by an even greater margin if we don't address the causes of climate change and move away from fossil fuels, according to the study.

Study lead author Christopher Merchant, a professor in ocean and Earth observation at the University of Reading, U.K., said the oceans generally dictate the pace for global warming as a whole because they are Earth's main heat sink and absorb heat from the atmosphere. This means if ocean warming is accelerating, then it's a sign that climate change is accelerating too.

"Nature might do something different next, but on current trends, the world is warming faster than we have been used to," Merchant told Live Science in an email. "That means all the impacts are coming at us faster."

Global warming drives rising sea levels that threaten coastal communities, fuels more extreme weather and dries out land, compromising our ability to grow food. Scientists have warned that unchecked climate change will bring untold suffering to billions of people while driving a third of Earth's species to extinction.

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Merchant and his colleagues used satellite data to model changes in average global sea surface temperatures over multiple decades. The team found an upward trend of warming alongside natural variations driven by events such as El Niño.

The team linked the accelerated ocean warming to climate change and Earth taking in more energy than it's emitting — a phenomenon called Earth's energy imbalance. Greenhouse gases such as carbon dioxide (CO₂) and methane (CH₄) trap heat in the atmosphere, which warm up the planet, and subsequently the oceans. This process, along with other human activities and natural variations, is a significant driver of Earth's energy imbalance, which has doubled within the last two decades.

Merchant noted that the warming ocean trend has picked up in the last 15 years because Earth is absorbing more sunlight as well as heat trapped by greenhouse gases. Researchers believe this increased sunlight absorption is linked to reduced cloud cover, meaning more sunlight penetrates Earth. Global warming also reduces snow and ice cover that would otherwise reflect sunlight back into space.

The study authors noted that the rate of surface ocean warming, and therefore global warming, over the last four decades isn't a guide for what's to come, and that much greater warming is expected if climate change isn't successfully mitigated.

"If we want to stabilize the climate, we should multiply our efforts to power our lifestyles without fossil fuels," Merchant said. "The good news is that significant transformation is already underway worldwide."