def aerocom_n(x, bc, oc, so2, nh3):
    """ERFari linear in emissions including nitrate

    Inputs
    ------
    x : obj:`numpy.array`
        Time series of aerosol emissions
    bc : float
        Radiative efficiency of black carbon, W m**-2 (TgC yr**-1)**-1
    oc : float
        Radiative efficiency of organic carbon, W m**-2 (TgC yr**-1)**-1
    so2 : float
        Radiative efficiency of sulfate (expressed as SO2 emissions),
        W m**-2 (TgSO2 yr**-1)**-1
    nh3 : float
        Radiative efficiency of nitrate (expressed as NH3 emissions),
        W m**-2 (TgSO2 yr**-1)**-1

    Returns
    -------
    res : obj:`numpy.array`
        Time series of ERFari
    """
    return bc*x[0] + oc*x[1] + so2*x[2] + nh3*x[3]