Low-Cloud Feedbacks from Cloud-Controlling Factors: A Review

Details

• Journal Title:
  Surveys in Geophysics
• Personal Author:
  Klein, Stephen A. ; Hall, Alex ; Norris, Joel R. ; Pincus, Robert
• NOAA Program & Office:
  OAR (Oceanic and Atmospheric Research) ; PSL (Physical Sciences Laboratory) ; CIRES (Cooperative Institute for Research in Environmental Sciences)
• Description:
  The response to warming of tropical low-level clouds including both marine stratocumulus and trade cumulus is a major source of uncertainty in projections of future climate. Climate model simulations of the response vary widely, reflecting the difficulty the models have in simulating these clouds. These inadequacies have led to alternative approaches to predict low-cloud feedbacks. Here, we review an observational approach that relies on the assumption that observed relationships between low clouds and the “cloud-controlling factors” of the large-scale environment are invariant across time-scales. With this assumption, and given predictions of how the cloud-controlling factors change with climate warming, one can predict low-cloud feedbacks without using any model simulation of low clouds. We discuss both fundamental and implementation issues with this approach and suggest steps that could reduce uncertainty in the predicted low-cloud feedback. Recent studies using this approach predict that the tropical low-cloud feedback is positive mainly due to the observation that reflection of solar radiation by low clouds decreases as temperature increases, holding all other cloud-controlling factors fixed. The positive feedback from temperature is partially offset by a negative feedback from the tendency for the inversion strength to increase in a warming world, with other cloud-controlling factors playing a smaller role. A consensus estimate from these studies for the contribution of tropical low clouds to the global mean cloud feedback is 0.25 ± 0.18 W m−2 K−1 (90% confidence interval), suggesting it is very unlikely that tropical low clouds reduce total global cloud feedback. Because the prediction of positive tropical low-cloud feedback with this approach is consistent with independent evidence from low-cloud feedback studies using high-resolution cloud models, progress is being made in reducing this key climate uncertainty.
• Keywords:
  Climate Change Cloud Feedbacks Low Clouds Climate Change Cloud Feedbacks Low Clouds
• Source:
  Surv Geophys 38, 1307–1329 (2017)
• DOI:
  https://doi.org/10.1007/s10712-017-9433-3
• Document Type:
  Journal Article
• Rights Information:
  CC BY
• Compliance:
  Submitted
• Main Document Checksum:
  urn:sha256:2a3730e6bfa465d358980105b1ae7780c74f08bebbfb894a099a34a68b3ce468
• Download URL:
  https://repository.library.noaa.gov/view/noaa/31044/noaa_31044_DS1.pdf
• File Type:
  [PDF - 844.17 KB ]