Researchers: Weather has become increasingly erratic

University students used to battling the rain one day and wearing flip flops the next will be unsurprised to learn that daily weather has become more erratic over the past couple of decades, according to University researchers.

In one of the first studies to investigate day-to-day climate variations, the scientists found that exceptionally sunny or cloudy days have become increasingly common since the early 1980s, as have swings between dry and stormy days since the late 1990s.

This change implies significant variability in solar radiation and precipitation for 35 percent of the world, and could result in increased levels of carbon dioxide in the atmosphere — with consequences for ecosystem stability, pest and disease control and the agriculture and solar energy industries.

The researchers said they found some of the largest impacts in tropical regions such as the rainforests of Africa, Southeast Asia and the Amazon. These sweeping changes are associated with the formation of large, powerful convective clouds that can also affect weather in more temperate northern areas.

“The atmosphere is like a fluid,” explained assistant geosciences professor and the study’s lead author David Medvigy. “The formation of these clouds in the tropics actually has a ripple effect that propagates to other areas of the atmosphere and could affect weather and climate at remote locations.”

Climate variations have historically been observed in terms of monthly averages, but there are many dynamics that make monthly averages obscure, Medvigy explained. In their study, Medvigy and Claudie Beaulieu, co-author and postdoctoral research fellow of the Program in Atmospheric and Oceanic Sciences, used new computer and satellite technology to observe weather on a daily scale.

High frequency weather variability holds implications for any process reliant on climate, most notably solar energy production and terrestrial plant photosynthesis.

“The amount of carbon dioxide will affect Earth’s climate, and that is something of interest to us all,” Medvigy said. “This day-to-day variability in sunshine and in rainfall strongly controls plant photosynthesis and respiration. And so if you change this atmospheric variability, you will change the ability of vegetation to take carbon out of or to release it to the atmosphere.”

Medvigy and his colleagues published a separate paper last year that investigated how weather variability would affect terrestrial ecosystems in the Eastern United States and Canada. They found that any increase in variability would reduce the amount of carbon stored in ecosystems and cause changes in ecosystem composition from evergreen to deciduous forests.

“The implications of changes in variability could be substantial, and I think that putting a number on it is going to require a little more work,” Medvigy said.

He added that he doesn’t think scientists truly understand the physical mechanism behind the observed increase in variability.

“So is variability in the future going to continue to increase, or is it going to drop off?” Medvigy asked. “Determining the mechanisms that are going to control the level of variability is an essential research task.”