The time lag between a carbon dioxide emission and maximum warming increases with the size of the emission

In a recent letter, Ricke and Caldeira (2014 Environ. Res. Lett. 9 124002) estimated that the timing between an emission and the maximum temperature response is a decade on average. In their analysis, they took into account uncertainties about the carbon cycle, the rate of ocean heat uptake and the climate sensitivity but did not consider one important uncertainty: the size of the emission. Using simulations with an Earth System Model we show that the time lag between a carbon dioxide (CO2) emission pulse and the maximum warming increases for larger pulses. Our results suggest that as CO2 accumulates in the atmosphere, the full warming effect of an emission may not be felt for several decades, if not centuries. Most of the warming, however, will emerge relatively quickly, implying that CO2 emission cuts will not only benefit subsequent generations but also the generation implementing those cuts.