A new study has found that daily weather in many parts of the planet have become more erratic.

The study, which is the first global climate study to focus on the variation in day-to-day weather, has found that in certain places, daily weather is increasingly changing between sunny and cloudy, and wet and dry days.

According to David Medvigy, the lead researcher and an assistant professor in the department of geosciences at Princeton University, the study is particularly important because increases in weather fluctuations can affect plants which currently pull about 25 percent of the greenhouse gas carbon dioxide emitted by humans out of the air.

Fluctuations in water and sunlight can reduce photosynthesis, the process by which plants use carbon dioxide and water to create sugars and oxygen, to make the planet's air breathable and feed the rest of the food chain. It can also cause a change in the composition of the ecosystems.

For the study, the researchers looked at data gathered by satellites on radiation bouncing off the Earth from 1984 to 2007 which showed that variability in sunlight reaching the surface changed significantly over 35 percent of the planet, primarily over tropical land in Africa and Asia, and seasonally in parts of the Amazon.

Over the same period, the flip-flopping between sunny and cloudy days increased on average by just under 1 percent a year, reaching a total change of 20 percent for the whole study period.

Medvigy and co-researcher Claudie Beaulieu also used precipitation data collected by satellites and rain gauges from 1997 to 2007 around the globe and they found that changes in variability of precipitation overlapped with the increased fluctuations in solar radiation. A 25 percent increase in the variability in precipitation over the 11-year period was seen in these regions.

Medvigy and Beaulieu said it's not clear why daily sunlight and precipitation are becoming more variable in parts of the world, but they suspect it may have something to do with giant convective clouds created by rising warm air. These clouds, which play a role in rainfall and in blocking sunlight from reaching the ground, were found over areas where the changes in variability occurred, they said.

Ther researchers are now investigating the connection between these clouds and the increases in weather variability.