7.4 Reading: Planetary boundaries
7.4 Reading: Planetary boundaries 1. What are the nine planetary boundaries? These nine planetary boundaries are · Climate change (CO2 concentration in the atmosphere <350 ppm and/or a maximum change of +1 W m-2 in radiative forcing); · Ocean acidification (mean surface seawater saturation state with respect to aragonite ≥ 80% of pre-industrial levels); · Stratospheric ozone (<5% reduction in O3 concentration from pre-industrial level of 290 Dobson Units); · Biogeochemical nitrogen (N) cycle (limit industrial and agricultural fixation of N2 to 35 Tg N yr-1) and phosphorus (P) cycle (annual P inflow to oceans not to exceed 10 times the natural background weathering of P); · Global freshwater use (<4000 km3 yr-1 of consumptive...