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What Do The 2024 Record High Temperatures Mean for Our Planet?

From fueling extreme weather to impacting marine life, these changes are reshaping our planet

It was 2012, and I was doing my PhD in Australia. While I was working with paleontological questions, my two best friends were doing their fieldwork in the Great Barrier Reef. They were scuba diving in research stations only licensed scientists could access.

I was looking forward to having them back from their trip. They proudly shared the pictures they had taken of underwater seascapes.

Four years later, having graduated with their PhDs and landed positions in other countries, their supervisor broke the terrible news: 2016’s extreme temperatures had led to the third mass-bleaching event in the reef. There were side-by-side pictures of corals they had photographed that had turned bright white.

But it didn’t end there, as temperatures kept creeping up, we experienced four more mass bleaching events: 2017, 2020, 2022, and… 2024. Of course, the warmest year on record did bring more than heat, fires, and floods. It also affected the very ecosystems that sustain healthy oceans. And with them, our future livelihoods.

Throughout these years, I have dedicated more and more of my research, first, and of my outreach efforts, later on, to communicating the science behind climate change. Ultimately, this is why I doubled down on my communication efforts:

Science communication is the bridge between knowing and doing. When people understand the science behind climate change, they care. When they care, they act. It’s our duty as scientists to make the science clear, relatable, and impossible to ignore. 🌍 #SciComm #ClimateAction

Silvia PM, PhD is Climate Ages (@climateages.bsky.social) 2025-01-10T02:11:46.913Z

Indeed, it’s now official that 2024 shattered records as the hottest year ever recorded on Earth and in the world’s oceans. And this warming isn’t just happening at the surface. It extends deep into the ocean, down to depths of 2,000 meters, where most of the extra heat from global warming has been quietly accumulating for decades.

These findings, published in Advances in Atmospheric Sciences by a team of 54 scientists from seven different countries, reveal how quickly our oceans are changing and how those changes are affecting life both above and below the surface.

Professor Lijing Cheng, who led the research, put it bluntly: “The broken records in the ocean have become a broken record.” Indeed, new heat records have become disturbingly routine.

Global upper 2000 m OHC from 1958 through 2024 according to (a) IAP/CAS, (b) CIGAR-RT, and © Copernicus Marine (1 ZJ = 1021 J). The black line in (a, b) shows monthly values, and the histogram presents annual anomalies. The time series are relative to the 1981–2010 baseline for IAP/CAS and CIGAR-RT data, and the 2005 baseline for the Copernicus Marine data. The 2005 values for IAP/CAS and CIGAR-RT data are 78 ZJ and 108 ZJ relative to the 1981–2010 baseline, respectively. The green bars indicate the uncertainty estimates from different datasets — Cheng, L., Abraham, J., Trenberth, K.E. et al. Record High Temperatures in the Ocean in 2024. Adv. Atmos. Sci. (2025). https://doi.org/10.1007/s00376-025-4541-3

But let’s backtrack a little bit. I like transparency in how science is done and I strive to provide you with the behind-the-scenes of our little worlds. So, how was the study performed?

To measure ocean heat content, the researchers used three independent datasets: observations from the Institute of Atmospheric Physics, Copernicus Marine Service, and the CIGAR reanalysis system. These sources rely on millions of ocean temperature readings collected by Argo floats, research vessels, and other monitoring tools.

Together, they create a highly detailed picture of how heat is spreading in the upper layers of the ocean over time.

The most striking result? In 2024 alone, the ocean’s heat content jumped by 16 Zettajoules. As a reference, this is an amount of energy so massive that it’s 140 times the total electricity generated worldwide in 2023. Worldwide.

But what else do the results tell us?

The findings confirm what climate scientists have warned about for years: the ocean is warming faster than ever. Surface temperatures were up by 0.61°C compared to the 1981–2010 average.

That made 2024 the hottest year on record for sea surface temperatures as well.

Global SST changes from 1955 through 2024 (units °C). Upper panel: The thick lines are the annual values, and the thin lines are the monthly values. The anomalies are relative to a 1981–2010 baseline. The within-year variation of SST is shown in the inner box, with 2024 values shown in red. Lower panel: Global annual mean SST changes from three data products (ERSST, Copernicus Marine, and IAP/CAS) — Cheng, L., Abraham, J., Trenberth, K.E. et al. Record High Temperatures in the Ocean in 2024. Adv. Atmos. Sci. (2025). https://doi.org/10.1007/s00376-025-4541-3

Why does this matter? Well, because the ocean’s surface heat drives weather patterns. From hurricanes to heatwaves, the ocean plays a pivotal role in shaping extreme weather events.

For instance, some regions, like the Atlantic Ocean, the Mediterranean Sea, and parts of the Southern Ocean, experienced especially intense warming. Dr. Karina von Schuckmann, a scientist from Mercator Ocean International, explained why this matters: “The ocean is our sentinel for planetary warming.” The researcher noted that oceans act like giant heat sponges, soaking up more than 90% of the excess energy trapped by greenhouse gases. But if the ocean crumbles, so do we.

Image 1

Another co-author of the study, Professor John Abraham, added, “To know what is happening to the climate, the answer is in the ocean.” That’s because warmer oceans aren’t just bystanders; they play an active role in our climate system. In fact, oceans orchestrate our climate.

Oceans fuel stronger storms, release more water vapor into the atmosphere, and drive weather extremes like floods, droughts, and heat waves.

Yes, that was the ocean.

You may be asking though, why does this matter?

This isn’t just abstract data; it’s happening already and reshaping our world. Over the past year alone, 104 countries hit their hottest-ever recorded temperatures. Wildfires intensified across parts of Europe and the Americas. Southern Asia experienced severe droughts, and hurricanes caused billions of dollars in damage across the United States.

See? We all pay the consequences—unfortunately, some more than others.

Differences of annual mean upper 2000 m OHC values between 2024 and 2023, based on (a) IAP/CAS analysis and (b) CIGAR-RT . Units: 109 J m−2 [data updated from Cheng et al. (2024a)] — Cheng, L., Abraham, J., Trenberth, K.E. et al. Record High Temperatures in the Ocean in 2024. Adv. Atmos. Sci. (2025). https://doi.org/10.1007/s00376-025-4541-3

Dr. Kevin Trenberth, a senior scientist involved in the study, explained why this is happening: “The main way the ocean continues to influence the climate is through accompanying increases in water vapor in the atmosphere. That leads to damaging increases in extremes in the hydrological cycle.”

In other words, when the oceans warm, they release more water vapor, which fuels extreme weather events like torrential rains or prolonged dry spells by moving these clouds away from where they used to release their water.

But it’s not just the atmosphere feeling the impact, either. As I explained earlier in this essay, warmer oceans are throwing marine ecosystems into chaos. Coral reefs are being devastated by heat stress, fish populations are migrating away from traditional fishing grounds, and coastal communities are facing economic and food security challenges.

A series of cascading events that go beyond the “it’s just warmer” picture some are trying to paint.

Regional observed upper 2000 m OHC change from 1958 through 2024 relative to a 1981–2010 baseline using IAP/CAS data. The time series (black lines) are smoothed by LOWESS with a span width of 240 months. The gray shaded areas are the 95% confidence intervals [data updated from Cheng et al. (2024a)] — Cheng, L., Abraham, J., Trenberth, K.E. et al. Record High Temperatures in the Ocean in 2024. Adv. Atmos. Sci. (2025). https://doi.org/10.1007/s00376-025-4541-3

Now let’s move forward. What does this mean for our future?

This study makes something clear: the warming of our oceans is a loud wake-up call to act now to reduce greenhouse gas emissions and slow global warming.

Over the years, scientists have come to realize that oceans are essentially the planet’s health barometer. Their record-breaking heat shows just how fast climate change is happening and how fast the ocean’s health is deteriorating.

But while the outlook is alarming, understanding these changes also gives us tools to take action. By protecting vulnerable marine habitats, adapting coastal infrastructure, and adopting bold carbon reduction policies, we can still work toward a future where our oceans and our planet are healthier. We can’t lose sight that there’s always something we can still do.

The time to act is now, and while the challenge is massive, there’s still hope to pave a more sustainable path forward.


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