Question i): Roles of external influences

What were the roles of external influences on climate evolution during the early Anthropocene?

Newly available observed data for the last two centuries are analyzed individually and interpreted, based on observations only and in conjunction with coupled model simulations, to arrive at estimates of the contribution to temperature change by greenhouse gas increases, other anthropogenic influences (including aerosols and land use change), solar forcing, volcanism, and internal climate variability. Because the role of external influences and climate variability can be separated more effectively based on a longer time horizon (see Hegerl et al., 2006), this reduces uncertainty in these estimates.