A new sea surface temperature (SST) reconstruction (Pan et al., 2026) uses mollusc fossil evidence to affirm southern Australia’s (Yorke Peninsula) SSTs were 4°C warmer than today (23°C versus 19°C) during both the mid-Holocene (MH, 8000 to 5000 years ago) and Last Interglacial (LIG, 125,000 to 116,000 years ago).

Both the MH and LIG had allegedly “safe” CO2 levels, ranging from 265 to 275 ppm. Sea levels were nonetheless 1-3 meters (MH) to 2-5 meters (LIG) higher than today along the Yorke Peninsula.

Interestingly, SSTs varied by “as much as 5-6°C” across multi-millennial timescales during the MH and LIG despite the low and stable CO2 levels.

None of these data points support the contention that CO2 is a driver of either ocean warming or sea level rise.

Image Source: Pan et al., 2026