In:
Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 18, No. 23 ( 2018-12-11), p. 17529-17543
Abstract:
Abstract. Climate sensitivity in Earth system models (ESMs) is an emergent
property that is affected by structural (missing or inaccurate model physics)
and parametric (variations in model parameters) uncertainty. This work
provides the first quantitative assessment of the role of compensation
between uncertainties in aerosol forcing and atmospheric parameters, and
their impact on the climate sensitivity of the Community Atmosphere Model,
Version 4 (CAM4). Running the model with prescribed ocean and ice conditions,
we perturb four parameters related to sulfate and black carbon aerosol
radiative forcing and distribution, as well as five atmospheric parameters
related to clouds, convection, and radiative flux. In this experimental setup
where aerosols do not affect the properties of clouds, the atmospheric
parameters explain the majority of variance in climate sensitivity, with two
parameters being the most important: one controlling low cloud amount, and
one controlling the timescale for deep convection. Although the aerosol
parameters strongly affect aerosol optical depth, their impacts on climate
sensitivity are substantially weaker than the impacts of the atmospheric
parameters, but this result may depend on whether aerosol–cloud interactions
are simulated. Based on comparisons to inter-model spread of other ESMs, we
conclude that structural uncertainties in this configuration of CAM4 likely
contribute 3 times more to uncertainty in climate sensitivity than
parametric uncertainties. We provide several parameter sets that could
provide plausible (measured by a skill score) configurations of CAM4, but
with different sulfate aerosol radiative forcing, black carbon radiative
forcing, and climate sensitivity.
Type of Medium:
Online Resource
ISSN:
1680-7324
DOI:
10.5194/acp-18-17529-2018
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2018
detail.hit.zdb_id:
2092549-9
detail.hit.zdb_id:
2069847-1
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