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CMIP5 Models Simulating Southeast Pacific Stratocumulus Clouds
Reference
Lin, J.-L., Qian, T. and Shinoda, T. 2014. Stratocumulus clouds in Southeaster Pacific simulated by eight CMIP5-CFMIP global climate models. Journal of Climate 27: 3000-3022.

Background
The authors write that stratocumulus clouds in the tropics and subtropics have come to be known as "climate refrigerators," in light of the likelihood that "a 5% increase of their coverage would be sufficient to offset the global warming induced by doubling CO2," due to their reflecting of an enhanced amount of incoming sunlight back to space, citing the confirming studies of Randall et al. (1984), Slingo (1990), Bretherton et al. (2004) and Wood (2012).

What was done
Lin et al. examined stratocumulus clouds and associated cloud feedback in the southeast Pacific (SEP), as simulated by eight global climate models that participated in phase 5 of the Coupled Model Intercomparison Project (CMIP5), as well as the Cloud Feedback Model Intercomparison Project (CFMIP), based on "long-term observations of clouds, radiative fluxes, cloud radiative forcing (CRF), sea surface temperature (SST), and [the] large-scale atmospheric environment."

What was learned
The three researchers say their results showed that "state-of-the-art global climate models still have significant difficulty in simulating the SEP stratocumulus clouds and associated cloud feedback." More specifically, and compared with observations, they report that (1) "the models tend to simulate significantly less cloud cover," as well as (2) "higher cloud tops," (3) "a variety of unrealistic cloud albedos," (4) "overly weak shortwave cloud radiative forcing," (5) "biases in large-scale temperature structure," including (5a) "lack of temperature inversion," (5b) "insufficient lower troposphere stability [LTS]," and (5c) "insufficient reduction of LTS with local SST warming," along with (6) "improper model physics" as it pertains to "insufficient increase of low cloud cover associated with larger LTS."

What it means
These findings represent but one group of global climate model failures to adequately "predict the past," which should provide us with ever more reasons to not trust the projections of future climate by even the best climate models in use today.

References
Bretherton, C.S., Uttal, T., Fairall, C.W., Yuter, S., Weller, R., Baumgardner, D., Comstock, K., Wood, R. and Raga, G. 2004. The EPIC 2001 stratocumulus study. Bulletin of the American Meteorological Society 85: 967-977.

Randall, D.A., Coakley, J.A., Fairall, C.W., Knopfli, R.A. and Lenschow, D.H. 1984. Outlook for research on marine subtropical stratocumulus clouds. Bulletin of the American Meteorological Society 65: 1290-1301.

Slingo, A. 1990. Sensitivity of the earth's radiation budget to changes in low clouds. Nature 343: 49-51.

Wood, R. 2012. Stratocumulus clouds. Monthly Weather Review 140: 2373-2423.

Reviewed 2 July 2014