There is uncertainty around the maximum sea surface temperatures. These are calculated using δ18O values from marine rocks, and there is an ongoing debate about the levels δ18O in Cambrian seawater relative to the rest of the Phanerozoic. Estimates for tropical sea surface temperatures vary from c. , to c. . Modern average tropical sea surface temperatures are .
there is uncertainty around the maximum sea surface temperatures these are calculated using δ18o values from marine rocks and there is an ongoing debate about the levels δ18o in cambrian seawater relative to the rest of the phanerozoic estimates for tropical sea surface temperatures vary from c  to c  modern average tropical sea surface temperatures are 