New Study Shows Deep Oceans Cooler Today Than 4.5 Million Years Ago

A new study finds the Earth’s bottom water temperatures (BWTs) have cooled by 2-3°C over the last 4.5 million years through to the preindustrial era (1750)

Since 1750, however, global BWTs have not risen in a detectable way, nor have they exceeded the warmth achieved during the Medieval Warm Period (Gebbie and Huybers, 2019).

The Pacific Ocean as a whole has continued to cool over the last centuries.

Image Source: Clark et al., 2025 and Gebbie and Huybers, 2019

Regionally, today’s North Atlantic’s bottom water temperatures hover around 4°C – just as they did throughout the Late Holocene.

The BWTs averaged ~5°C, or “slightly warmer than present-day,” during the last glacial, with anomalies reaching 10°C both 13,000 and 16,000 years ago and about 7°C both 15,000 and 19,000 years ago (Yasuhara et al., 2019).

Image Source: Yasuhara et al., 2019

As recently as 10,000 years ago, the Arctic Ocean’s bottom water temperatures were 6-10°C warmer than they are today (Beierlein et al., 2015).

These global and regional BWT reconstructions do not support the narrative that modern ocean temperatures are unprecedentedly warm due to human activity.

See more here climatechangedispatch

Header image: Shutterstock

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Comments (1)

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    Tom

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    While this could be true, they are guessing at temps going back 4.5 million years. I expect the earth is still cooling off from the inside out after 3-4 billion years. No matter, global warmer is the biggest scam since vaccines.

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