The emissions limits in this study were prescribed such that they were approximately consistent with a stabilization of atmospheric concentration of CO2 at the level of 550 parts per million (ppm). With the inclusion of the radiative forcing associated with other non-CO2 greenhouse gases, this stabilization level is approximately a 675 ppm CO2-equivalent limit.

From here.

Seems high to me too. The model explicitly excludes carbon cycle feedbacks, which could already be in play. My preference is Hansen’s 350…