def skin_temperature(upward_longwave_irradiance_W_m2, emissivity=1.0):
    """
    Calculates the radiative skin temperature from the upward longwave irradiance.

    Args:
        upward_longwave_irradiance_W_m2: The upward longwave irradiance from the surface
        emissivity: How much energy is emitted in comparison to a blackbody. Ranges from 0 to 1.

    Returns:
        The skin temperature in Kelvin.
    """
    sigma = 5.673067e-8
    return (upward_longwave_irradiance_W_m2 / (emissivity * sigma)) ** 0.25