Graphene is theoretically expected to be a highly suitable material for spintronic and quantum computation applications. Current experimental reports assign surprisingly low spin lifetimes to graphene and related carbon structures. Recently, we showed a solvothermal synthesis method that can be employed to produce a high-purity sample, which approximates very well the assembly of graphene sheets. Using the contactless spectroscopic technique of electron spin resonance (ESR), we were able to identify in this graphene material the ESR of both conduction electrons and localized spins [Nafradi et al., Carbon 74, 346-351 (2014)]. Here, we show the temperature dependent evolution of the ESR of these two spin species. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim