Are there scientifically and politically viable ways to counter-act the most serious consequences of human-induced climate change (i.e., loss of the Arctic, diversion of storm tracks, intensification of weather extremes, acidification of the environment, etc.) for at least the several decades of peak climate change that are inevitable even in the face of aggressive international action? How much more intensive would the impacts and counter-acting actions have to be if international action is delayed for several decades?

With fossil fuels providing about 80% of global energy, it is going to take decades to decarbonize the energy system even with aggressive mitigation. As a result, it is virtually inevitable that the warming will head well past 2 C, leading to significant and likely irreversible impacts to climate, the environment, sea level, and acidification. The only potential way to keep the increase in global average temperature increase below 2 C (especially as SO2 emissions and aerosols decrease) and to limit some of the most severe impacts (e.g., to save the Arctic) is going to be to take counter-acting actions (often called geoengineering), We must determine if the potential to take such actions is scientifically justifiable, environmentally effective, and societally and politically acceptable–if research proves this so, we should be preparing to start soon to offset each year’s warming influence and perhaps take the climate back several decades; if not, we need to redouble and redouble our mitigation efforts.