Abstract
Cloud radiative feedbacks are currently the largest source of spread in
estimates of climate sensitivity. Here we examine how cloud feedbacks
relate to biases in model simulations of present-day clouds relative to
NASA Multiangle Imaging SpectroRadiometer (MISR) satellite observations.
Specifically, we examine relationships between bias in cloud fraction,
cloud-top-height, and cloud optical depth with tropical high cloud,
midlatitude low cloud, global high-cloud altitude, and tropical low
cloud feedbacks for CMIP5 and CMIP6 models that have produced MISR
simulator output. We find that the strength of all four of these
simulated cloud feedbacks have statistically significant relationships
with biases in present-day simulations of clouds. We use these
relationships in an emergent constraint analysis to narrow the spread in
the strength of each feedback. This suggests that future expert
assessments of cloud feedbacks (and climate sensitivity) should consider
present day biases in clouds and the climate modeling community might
consider undertaking simulations where models are systematically tuned
to eliminate (or at least reduce) biases relative to satellite
observations.