  We develop a theoretical model to describe the dissipative dynamics of
singlet-triplet (S-T_0) qubits in GaAs quantum dots. Using the concurrence
experimentally obtained as a guide, we show that each logical qubit is coupled
to its own environment because the decoherence effect can be described by
independent dephasing channels. Given the correct description of the
environment, we study the dynamics of concurrence as a function of the
temperature, the constant coupling between the system and the environment, the
preparation time, and the exchange coupling. Although the reduction of the
environment coupling constant modifies the entanglement dynamics, we
demonstrate that temperature emerges as a crucial variable and a variation of
millikelvins significantly modifies the generation of entangled states.
Furthermore, we show that the exchange coupling together with the preparation
time strongly affects the entanglement dissipative dynamics.
