Among other forcings, past climate variations have been driven by changes in Earth’s orbit and greenhouse gas concentrations. These forcings often change concurrently, making it difficult to isolate specific climate responses from the paleoclimate record alone. Here, simulations are run with the NCAR CESM1.2 to isolate the climate responses to different past forcings. In each simulation, only one boundary condition is changed while others remain fixed at preindustrial levels, with the goal of isolating the climate response to individual forcings. The experiments are described below. In each simulation, parameters not mentioned are the same as the preindustrial simulation.
Simulations:
· 0ka_0urb: A preindustrial simulation, with the following parameters: Obliquity: 23.44107°; Longitude of perihelion: 102.7242°; eccentricity: 0.01670772; CO2: 284.7 ppm; Ice sheets: 0 ka.
· lo_obliq and hi_obliq: Obliquity is set to 22.079° or 24.480°, respectively.
· 0_AEQ, 90_WSOL, 180_VEQ, and 270_SSOL: Longitude of the perihelion is set to 0°, 90°, 180°, or 270°. This corresponds to perihelion at the Northern Hemisphere autumnal equinox, winter solstice, vernal equinox, or summer solstice, respectively. Eccentricity is set to 0.0493.
· ECC_0: Eccentricity is set to 0, resulting in a perfectly circular orbit.
· half_CO2: CO2 is set to 142.35 ppm, half of its preindustrial level.
These simulations have been discussed in Erb et al., 2018: Model evidence for a seasonal bias in Antarctic ice cores, Nature Communications, and Bosmans et al, 2018: Response of the Asian summer monsoons to idealized precession and obliquity forcing in a set of GCMs, Quaternary Sci. Rev. Please inform the authors if you use these simulations.
Computing resources (ark:/85065/d7wd3xhc) were provided by the Climate Simulation Laboratory at NCAR’s Computational and Information Systems Laboratory, sponsored by the National Science Foundation and other agencies.
