The UTCI and the ISB.

Thermal effects of the environment are the most prominent environmental influences on the human body. Keeping the body core temperature in a narrow optimum range is the dominating physiological process. Thus, assessing thermal environments has been a major field in biometeorology for many decades, which is also reflected in the number of respective articles and their citations. In the early days of thermal assessments, simple indices only considering a few environmental parameters were used. The next step has been the development of heat budget models describing all relevant heat/energy fluxes to and from the human body. One of the first was PET, which has been presented in the most cited IJBM publication ever (1999). All of these models created by individual scientists have some shortcomings and confinements in their application. In order to overcome such restrictions and to bring the state of the art scientists of thermal modelling together a working group to define a "universal" thermal climate index (UTCI) has been founded, backed and driven by an own commission of the International Society of Biometeorology. This working group has developed a comprehensive open source tool to calculate UTCI for the assessment of outdoor thermal environments for biometeorological applications (see the IJBM special issue 56 (2012) on UTCI).