vs HyCAM.ftorch.2d (10yr) and SPCAM (5yr). Thick = per-step, light = annual mean. B1850 trend lines per spin-up period: 0-3 yr +0.105 W/m² (short spin-up), 0-6 yr +0.062 W/m² (long spin-up), 6-20 yr +0.0035 W/m² (equilibrated/flat). Two-stage spin-up; equilibrated from ~year 6; no shocks at the 5/10/15-yr resubmit boundaries.
