For generations, human civilization has been building a climate debt, borrowing from the stability of the future to power the economic growth of the present. Through fossil fuel combustion and land use change, we have disrupted the carbon cycle, overwhelming the influence of natural forcing on Earth’s climate. As heat accumulates in the climate system, it drives long-term increases in temperature and sea level, and super-charges hurricanes, heatwaves, and heavy precipitation events. These changes in turn exacerbate poverty, hunger, disease, refugee crises, and more. Today, the choice is stark: can we do what it takes to avoid widespread dangerous change? Or will we remain mired in inaction until the full cost of this unprecedented experiment we’re conducting with our planet falls due?