Abstract
The scientific understanding of the Earth’s climate
system, including the central question of how the climate
system is likely to respond to human-induced perturbations,
is comprehensively captured in GCMs and Earth
System Models (ESM). Diagnosing the simulated climate response,
and comparing responses across different models, is
crucially dependent on transparent assumptions of how the
GCM/ESM has been driven – especially because the implementation
can involve subjective decisions and may differ
between modelling groups performing the same experiment.
This paper outlines the climate forcings and setup of the Met Office Hadley Centre ESM, HadGEM2-ES for the
CMIP5 set of centennial experiments. We document the prescribed
greenhouse gas concentrations, aerosol precursors,
stratospheric and tropospheric ozone assumptions, as well as
implementation of land-use change and natural forcings for
the HadGEM2-ES historical and future experiments following
the Representative Concentration Pathways. In addition,
we provide details of how HadGEM2-ES ensemble members
were initialised from the control run and how the palaeoclimate
and AMIP experiments, as well as the “emissiondriven”
RCP experiments were performed.