SI 1. Impulse response of the carbon cycle
In figure SI 1 we compare the impulse response to a pulse emissions of
CO2 in DICE 2016 2R to the pulse response used for calcluating Global
Warming Potentials (GWP) in IPCC AR5 (Myhre et al, 2013). The Impule
response used in IPCC AR5 chacterizes the impulse response close to
present days concentrations and is the basis for the carbon cycle in the
FAIR model. As can be seen in the figure, a substantially larger
fraction of a CO2 pulse emission stays in the atmosphere
for the carbon cycle in DICE 2016 R2 than in the carbon cycle in IPCC
AR5. However, it must be kept in mind that the carbon cycle is
non-linear and the removal rate decreases with increasing atmospheric
concentrations (which is considered in the revised carbon cycle, but not
in DICE-2016R2). The impulse response in DICE-2016R2 is likely to be
representable for far higher concentration than those compatible with
keeping the global mean surface temperature at or below 2.5 °C above the
pre-industrial level.