David Medvigy, an assistant professor in the Department of Geosciences at Princeton, and Claudie Beaulieu, a postdoctoral research fellow in Princeton’s Program in Atmospheric and Oceanic Sciences, believe that extremely sunny or cloudy days have become more common and that swings between stormy days and dry days have increased dramatically.

This has obviously occurred at a time when global temperatures have been rising, but it’s impossible to say for sure whether the increase in variability is being caused by climate change. On the one hand, a warmer world means there’s more energy in the atmosphere to generate dramatic weather with, but on the other hand, climate is merely an average of weather over a long period of time.

This increase in variability could have impacts on the stability of ecosystems and on industries like agriculture, renewable energy production and transport. “Our work adds to what we know about climate change in the real world and places the whole problem of climate change in a new light,” saud Medvigy. “Nobody has looked for these daily changes on a global scale. We usually think of climate change as an increase in mean global temperature and potentially more extreme conditions — there’s practically no discussion of day-to-day variability.”

He added: “If you don’t know what role variability is playing now, you’re not in a very strong position for making remarks about how it might change in the future,” he said. “We’re at a stage where we had better take a look at what this research is pointing out.”

The most extreme variations in weather were observed in the tropics, but those effects radiate around the glove, said William Rossow, a professor of earth system science and environmental engineering at the City College of New York. “Wherever it’s raining heavily, especially, or variably is where the atmosphere is being punched. As soon as it is punched somewhere in the tropics it starts waves that go all the way around the planet,” he said.

“Signals end up going over the whole globe, and whether they’re important in a particular place or not depends on what else is happening,” he added. “But you can think of storms as being the disturbances in an otherwise smooth flow. That’s why this is a climate issue even though we’re talking about daily variability in specific locations.”

The results of the study were published in the Journal of Climate.

from:    http://www.wired.co.uk/news/archive/2011-11/16/erratic-weather