Climate change is a cumulative problem. Every added molecule of CO2 loads the carbon budget further, adds to the extreme weather events we are already experiencing, and takes us one step closer to irreversible tipping points and runaway warming. Emissions today cannot be compensated by higher ambition tomorrow. A focus on emissions levels decades ahead, such as the recent weak G7 statement, is a dangerous distraction if not preceded by aggressive emissions reductions here and now. Pre-2020 action must be centre-stage for Paris.