On the correct use of cumulative applied climate indices for studying biological objects

The cumulative applied climate indices SAT and SET used in the Russian literature are considered in detail. These indices differ in calculation methods and, consequently, their values differ in different regions. The example is presented of the incorrect use of these indices by some authors for studying biological objects which leads to false conclusions. The method of calculation of the foreign applied climate index GDD is given. This index corresponds to the Russian index SET, and its interpretation as a counterpart of SAT is wrong.