Earth Temperature: A New Additive Global Climate Observable Defined Through Synthetic Global Modeling

Climate science relies heavily on averages, anomalies, and gridded reanalyses to describe global temperature. These approaches discard the majority of information contained in the instantaneous temperature field and obscure diurnal structure. This preprint introduces a new global climate observable: the instantaneous additive temperature of the Earth, defined as the sum of all local temperatures measured across the planet at a given moment. This observable — Earth Temperature — is additive, time‑aligned, and sensitive to diurnal, seasonal, and long‑term structure. To demonstrate its behavior and scientific value, I construct a synthetic global model of 100 representative cities distributed across latitudes and continents. The results show that Earth Temperature exhibits a well‑defined global diurnal cycle, a seasonal cycle, and a long‑term trajectory that differs fundamentally from global mean temperature. This work establishes the conceptual foundation for computing Earth Temperature from historical hourly station data and motivates the development of a global data infrastructure to support this new observable.