They accounted for that possibility: > One possible reason for the lower temperature estimates today than in the past is the difference in thermometers or meth

They accounted for that possibility: > One possible reason for the lower temperature estimates today than in the past is the difference in thermometers or methods of obtaining temperature. To minimize these biases, we examined changes in body temperature by birth decade within each cohort under the assumption that the method of thermometry would not be biased on birth year. I think that the assumption that the method of thermometry is not biased based upon birth year is probably correct.