Molecular thermometer, known as U^k₃₇ index, is used to estimate sea surface temperature (SST) based on unsaturation ration of long chain ketone in marine sediments. The production ratio of alkenones of the oceanic coccolithophrid Emiliania hyxleyi is linarly correlated with their growth temperature, and there is no alteration for this ratio during sedimentation and burial, so it is a good indicator for studies of paleoceanography and paleoclimate. This method is not affected by salinity, upwilling and polar ice volumn, so it extends the range of paleoclimatic studies to regions with carbonate poor sediments where any foraminiferal analyses are not possible.