def dt_dt(sdat):
    """Derivative of temperature.

    Compute dT/dt as a function of time using an explicit Euler scheme.

    Args:
        sdat (:class:`~stagpy.stagyydata.StagyyData`): a StagyyData instance.
    Returns:
        tuple of :class:`numpy.array`: derivative of temperature and time
        arrays.
    """
    temp, time, _ = sdat.tseries['Tmean']
    dtdt = (temp[1:] - temp[:-1]) / (time[1:] - time[:-1])
    return dtdt, time[:-1]