A team of University of Hawaii-Manoa researchers from the U.S. and Japan have solved one of the most deceptively difficult problems in climate science: What happens to clouds in a warming world? Are there more, or fewer, and do they make matters better or worse?
They report that a regional atmospheric model has achieved a breakthrough in the depiction of the impact of warming temperatures on cloudiness in the eastern Pacific Ocean, something that large global climate models have failed to accomplish.
It doesn't qualify as a dramatic Eureka! moment, but in climate science, progress on this front is a big deal, because this failure of the large, supercomputer-driven global climate models to accurately capture the role of clouds in our changing climate is a major source of uncertainty in their forecasts.
"All the global climate models we analyzed have serious deficiencies in simulating the properties of clouds in present-day climate," Discovery News quoted lead author Axel Lauer from the University of Hawaii team as saying.
"It is unfortunate that the global models' greatest weakness may be in the one aspect that is most critical for predicting the magnitude of global warming," Lauer added.
Unfortunately, the news apparently confirms earlier estimates that the response of clouds to rising sea surface temperatures amplifies the warming trend, leading scientists to suggest that our future lies at the warmer high end of the spread of model uncertainty rather than the cooler low end.
Higher sea surface temperatures cause low-level marine clouds to dissipate, the thinking goes, allowing more of the sun's warming rays to break through, causing a further rise in ocean temperatures. . . and so on.
In the same stretch of the eastern North Pacific, similar "positive feedback" results were reported last summer by a team led by Amy Clement of the University of Miami, who compared observations made by sailors with measurements taken by satellite-borne instruments, but is the first report of a model successfully capturing the effect.
"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 co-author Kevin Hamilton.
The findings have been reported in the Journal of Climate.