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Project Overview
Problems to be solved:
In order to quantify the potential climate impact of changing atmospheric
constituents such as 'greenhouse gases' two simple measures have been used,
namely 'Global Warming Potential' (GWP) and 'Radiative Forcing' (RF).
While these measures are convenient 'metrics' allowing estimation of. potential
climate change in terms of e.g. global mean temperatures from an emission
into the atmosphere of greenhouse gases, it has recently been found that
these
metrics have shortcomings, in particular when considering short lived,
chemically active and not well mixed chemical species.
Scientific objectives and approach
The objectives are to assess current metrics of climate change, e.g.
Radiative Forcing and Global Warming Potential as used in the Kyoto Protocol,
to refine
metrics of climate change, suitable for climate forcing agents arising
from inhomogeneously distributed perturbations of the atmosphere, e.g.,
aerosols, ozone,
contrails and from gases with different levels of thermal infrared
optical thickness and different atmospheric adjustment times, e.g., CO2
versus CH4, and to
evaluate the refined metrics with respect to their usefulness for policy
makers.
Several cases of localised emission perturbations of ozone precursors
will be defined. Using two different chemical transport models, the indirect
impact on
ozone and other greenhouse gases (e.g., methane) will be calculated
and radiative forcing will be determined.
Idealised and realistic cases of perturbations of climate change agents
will be defined. The equilibrium climate responses to these forcings will
be compared
using three different general circulation models, and the causes of
disagreement will be analysed.
A review of available metrics of climate change will be made. Available
metrics (like radiative forcing and global warming potential) will be applied
to the
simulations. Finally, on this basis it will be assessed in which cases
the current metrics are sufficiently good predictors of climate change.
Refined metrics will be
developed and it will be assessed under which circumstances metrics
are good predictors of climate change.
The requirements of policy makers for metrics of climate change will
be discussed and formulated. Current and refined metrics will be assessed
with respect to
their applicability as tools for decision making.
Expected impacts
The project will contribute to a further development of environmentally
effective policy measures under e.g. the UNFCCC and to better control and
regulation
of anthropogenic impact on the atmosphere and climate.