Erratic, Extreme Day-To-Day Weather Puts Climate Change in New Light

ScienceDaily (Nov. 15, 2011) — The first climate study to focus on variations in daily weather conditions has found that day-to-day weather has grown increasingly erratic and extreme, with significant fluctuations in sunshine and rainfall affecting more than a third of the planet.

Princeton University researchers recently reported in the Journal of Climate that extremely sunny or cloudy days are more common than in the early 1980s, and that swings from thunderstorms to dry days rose considerably since the late 1990s. These swings could have consequences for ecosystem stability and the control of pests and diseases, as well as for industries such as agriculture and solar-energy production, all of which are vulnerable to inconsistent and extreme weather, the researchers noted.

The day-to-day variations also could affect what scientists can expect to see as Earth's climate changes, according to the researchers and other scientists familiar with the work. Constant fluctuations in severe conditions could alter how the atmosphere distributes heat and rainfall, as well as inhibit the ability of plants to remove carbon dioxide from the atmosphere, possibly leading to higher levels of the greenhouse gas than currently accounted for.

Existing climate-change models have historically been evaluated against the average weather per month, an approach that hides variability, explained lead author David Medvigy, an assistant professor in the Department of Geosciences at Princeton. To conduct their analysis, he and co-author Claudie Beaulieu, a postdoctoral research fellow in Princeton's Program in Atmospheric and Oceanic Sciences, used a recently developed computer program that has allowed climatologists to examine weather data on a daily level for the first time, Medvigy said.

"Monthly averages reflect a misty world that is a little rainy and cloudy every day. That is very different from the weather of our actual world, where some days are very sunny and dry," Medvigy said.

"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," he said. "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."

The Princeton findings stress that analysis of erratic daily conditions such as frequent thunderstorms may in fact be crucial to truly understanding the factors shaping the climate and affecting the atmosphere, said William Rossow, a professor of earth system science and environmental engineering at the City College of New York.
"It's important to know what the daily extremes might do because we might care about that sooner," said Rossow, who also has studied weather variability. He had no role in the Princeton research but is familiar with it.

Rossow said existing climate-change models show light rain more frequently than they should and don't show extreme precipitation. "If it rains a little bit every day, the atmosphere may respond differently than if there's a really big rainstorm once every week. One of the things you find about rainstorms is that the really extreme ones are at a scale the atmosphere responds to," he said.

Although climate-change models predict future changes in weather as the planet warms, those calculations are hindered by a lack of representation of day-to-day patterns, Rossow said.

"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."

Medvigy and Beaulieu determined sunshine variation by analyzing fluctuations in solar radiation captured by the International Satellite Cloud Climatology Project from 1984 to 2007. To gauge precipitation, the researchers used daily rainfall data from the Global Precipitation Climatology Project spanning 1997 to 2007.

read more at link above..

November 16, 2011 – GEORGIA – Severe weather — including suspected tornadoes — swept through the South on Wednesday, killing one person and injuring at least four others, officials said. The fatality occurred in Forsyth County, Georgia, when a tree fell on a car, the fire department said. Four people were injured in Mississippi, but their injuries were not critical, according to National Weather Service reports. A possible tornado caused “major damage” to a mobile home park near Opelika, Alabama, with homes and vehicles demolished, the weather service said, citing an emergency manager in Lee County. It was not immediately known if anyone was injured. Downed trees, damaged homes and buildings, and power outages were reported across north, central and west Alabama and Georgia, including in metro Atlanta, from high winds and possible twisters. Georgia Power said it had 1,975 customers without power — 594 in metro Atlanta, 1,375 in the Manchester area, and scattered outages elsewhere. A high school in Harris County, Georgia, was also reported damaged. Eastern Alabama’s Lee County received “significant reports of damage,” said Rita Smith, a public information officer with Lee County Emergency Management. “We’ve got reports of damage at an apartment complex, structures at a lake, mobile homes and trees down,” she said. –CNN excerpt http://www.cnn.com/2011/11/16/us/severe-weather/index.html?eref=igoogledmn_topstories