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). [emphasis, links added]
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.
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).
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.
Read more at No Tricks Zone
