According to new research, marine organisms embedded in coastal rocks dating to ~6500 years ago indicate Northern Ireland’s sea levels were 7.8 m higher than today at that time.
As recently as 3400 years ago sea levels were still no lower than 5.6 m higher than today.
Image Source: Simms et al., 2026
Approximately 7000 to 6000 years ago biomarker evidence embedded in rock suggests Brazilian sea level was >2 m (3-3.5 m) higher than today (Anduro et al., 2026).
This equatorial region was minimally affected by post-glacial uplift. Thus, the 2 to 3.5 m higher relative sea level during this period likely represents the Holocene eustatic (water volume in ocean basins attributed to a less-glaciated Earth) sea level.
And what was the atmospheric CO2 concentration at that time?