New Study: Sea Levels Were 3 Meters Higher Than Today 5000 Years Ago Along Japan’s Coasts

Relative sea levels are lower today than at any time in the last 7000 years.

According to 80-year-old aerial photograph evidence, scientists (Nakanishi et al., 2024) report the coastline of their studied area (Hokkaido, Japan) has “receded by approximately 100 m seaward” since 1944. This is a continuation of the long-term, millennial-scale decline in relative sea level.

Accounting for crustal deformations, earthquakes, tsunamis, and vertical land movements (e.g., uplift), the authors conclude relative sea levels were “at least 1 m higher than the present sea level” about 2000 years ago, and a “maximum sea level of +3 m was obtained at 6-4 ka.”

So, ever since about 4000 years ago, when carbon dioxide levels were alleged to be a “safe” 265 ppm, relative sea levels have been falling and CO2 levels have been rising. This negatively correlated pattern has continued into the 20th and 21st centuries.