New UH Research: Warming to rise to high end of climate change estimates

One of the trickiest things in climate modeling is predicting what clouds will do.

That’s important, because heavy clouds reflect solar radiation, causing cooler conditions, and lower cloud cover let solar radiation reach the surface, increasing warming.

(Image: In this IPRC graphic, covering cloud cover over the Eastern Pacific for the past quarter century, the black line represents satellite-observed cloud cover, while the red line represents model-predicted cloud cover.)

New research done largely at the University of Hawai`i’s International Pacific Research Center (IPRC) is suggesting that clouds may thin when it’s warmer, meaning future climate change could be more severe than the most conservative estimates.

The researchers are conservative in their language, but they say their results are worrisome.

“If our model results prove to be representative of the real global climate, then climate is actually more sensitive to perturbations by greenhouse gases than current global models predict, and even the highest warming predictions would underestimate the real change we could see,” said IPRC researcher Kevin Hamilton.

It comes down to clouds.

“All the global climate models we analyzed have serious deficiencies in simulating the properties of clouds in present-day climate. It’s unfortunate that the global models’ greatest weakness may be in the one aspect that is most critical for predicting the magnitude of global warming,” said IPRC scientist Axel Lauer.

Researchers at the center have developed a new cloud prediction model that may help fine tune the predictive process. After developing their new model, they applied it to satellite imagery of the Eastern Pacific over the past 25 years. As the image with this post shows, it seems to be a pretty good match.

The center’s report on the research, “The Impact of Global Warming on Marine Boundary Layer Clouds over the Eastern Pacific—A Regional Model Study,” was written by University of Hawai`I scientists Lauer, Kevin Hamilton, Yuqing Wang and Vaughan Phillips, along with University of Wisconsin atmospheric scientist Ralf Bennartz. It was published in the Journal of Climate.

They call their new model iRAM, which is an acronym for something that already contains an abbreviation: IPRC Regional Atmospheric Model. In their careful terminology, they say that while this research may not be a slam dunk, it’s strongly suggestive that the ball goes through the hoop with some force (to poorly employ a sports analogy.)

“The iRAM results by themselves cannot be connected definitively to global climate feedbacks; however, among the (Global Climate Models) the cloud feedback in the full tropical–subtropical zone is correlated strongly with the east Pacific cloud feedback, and the cloud feedback largely determines the global climate sensitivity," the paper says.

In essence, the work suggests a troubling feedback mechanism may take place with continued warming, in which more warming means less clouds, which in turn means even more warming.

© Jan TenBruggencate 2010