For the first time, researchers have found evidence that global warming caused by humans is affecting clouds -- and not in a good way. A study by team from the Scripps Institution of Oceanography shows that clouds are being pushed up and out of mid-range latitudes toward the poles. "It's really the first credible evidence that we have of climate change and clouds in the observed record ," says Scripps atmospheric scientists Joel Norris. The cloud shift could push temperatures even higher than predicted, and also shows the need to improve atmospheric measurements.
Getting the data wasn't easy, as the team had to fix unreliable data from satellites with degrading sensors, shifted orbits and other problems. Once they figured out how to get rid of the artifacts, researchers found that storms in the middle latitudes both south and north of the equator had shifted toward the poles. In addition, the tops of the highest clouds had also moved upwards. That matches the scariest predictions created by computer climate models.
It's really the first credible evidence that we have of climate change and clouds in the observed record.
Fewer clouds means less precipitation in mid-latitudes, making arid regions more arid. However, it also reinforces global warming, as the mid-latitude areas that get the highest solar radiation have fewer clouds to reflect it back into space. In addition, the higher cloud tops trap more heat by increasing the size of the planet's "greenhouse."
As with any type of new study, there could be flaws. NASA scientist Kate Marvel points out that the cloud shifts could have been caused by two volcanoes that happened in the early '80s at the beginning of the study period (Mount St. Helens and Mexico's El Chicon). However, it shows a greater need for improved long-term observations by satellite and ground-based systems. "This study reminds us how poorly prepared we are for detecting signals that might portend more extreme climate changes than are presently anticipated," researcher Bjorn Stevens tells the Guardian.