Read here. During an extended period of low atmospheric levels of CO2, researchers find both higher and cooler Gulf of Mexico sea surface temperatures for prior historical periods. Solar activity correlation is indicated. (click on image to enlarge)
- "The researchers report that "two multi-decadal intervals of sustained high Mg/Ca indicate that Gulf of Mexico sea surface temperatures (SSTs) were as warm or warmer than near-modern conditions between 1000 and 1400 yr B.P.,....during the coolest interval of the Little Ice Age (ca. 250 yr B.P.) indicate that SST was 2-2.5°C below modern SST." In addition, they found that "four minima in the Mg/Ca record between 900 and 250 yr. B.P. correspond with the Maunder, Sporer, Wolf, and Oort sunspot minima.""